NZ223884A - Electrochromic device for electrically darkenable windows - Google Patents

Description

r< Priority Date(s): Complete Specification Filed: Class: <3 £>2 sbs. \<, i n DEC'1990" Publication Date: P.O. Journal. No: . Bcfl-. 2.? 3 8 3-1 NEW ZEALAND No.: Date: PATENTS ACT, 1953 COMPLETE SPECIFICATION NEW ZEALAND PATENT OFFICE 16NQVI990 RECEIVED ELBCTROCHROMIC DEVICE •>(yWe, IMPERIAL CHEMICAL INDUSTRIES PLC, A British company of, Imperial Chemical House, Millbank, London SW1P 3JF, ENGLAND hereby declare the invention for which <Ef/ we pray that a patent may be granted to r^c/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page 1A) -1A- 228884 SOLID ELECTROLYTES This invention relates to an electrochromlc device. Electrochromlc devices employing an electrolyte between two electrodes-, one of which Is a composite electrode comprising a so-called electrochromlc material, are known, eg. from 6B-A 1 540 713, EP-A 127 111 and EP-A 128 982.

In such known devices, the electrochromlc material will often comprise a higher oxidation state transition metal compound. The best known examples of such compounds include the so-called tungsten bronzes and related oxide bronzes. The electrochromlc (host) material (eg tungsten oxide) Interacts with guest atoms or ions (eg lithium in the case of tungstan oxide) or electrons fed to it by the application of an electrical potential to the device, In a manner which affects its interaction with incident electromagnetic radiation (eg a visible change of colourless tungsten oxide to blue).

In such known devices, the components are conveniently, in the form of thin layers, which are preferably essentially colourless and normally transparent or translucent in one state of the device (ie before a potential is applied across the electrodes to bring about an electrochromlc change in the electrochromlc material). Thus, typical known transparent conductive materials used for such electrodes include certain metal oxides and mixed oxides, such as indium and tin oxides, and their mixtures and solid solutions, coated conventionally on one face of a sheet which is transparent or translucent at the operating wavelengths, eg. a glass pane or a thermoplastic.

Such known devices usually require a fast conductor solid electrolyte. Polymeric semi-fluid electrolytes containing an alkali metal cation are often used, eg as described in Br. Poly. J..1975, 7, 319-327.

PAWNiT 16 NOV 1990 223334 Such semi-fluid plastics electrolytes require rigid containment and support for satisfactory robustness and operation. As described and claimed in our related New Zealand Patent Specification Mo. 221722 we have found that a specific type of solid electrolyte which contains liquid, is nevertheless advantageously dry in handling, Is dimensionally stable and flexible, and has good elastically resilient compression properties and unexpectedly good conductivity. The electrolyte is thus suitable for and enables the production of high energy density devices, eg batteries having an unexpectedly high power density (ie power per unit weight) and capacitors having an unexpectedly high capacitance density, similarly defined at room temperature. The electrolyte has also been found to be suitable for use in electrochromlc devices. The embodiments of this type of solid electrolyte further described hereinafter and used In the electrochromlc device of the present invention are known herein as the Sol id'Electrolyte.

Accordingly the present invention provides an electrochromlc device for electrically darkenable windows which comprises a pair of electrodes, at least one of which t3 tungsten oxId8 composite electrode, separated by the Solid Electrolyte.

In a preferred embodiment the electrodes and Solid Electrolyte are thin films, so that the electrochromlc device is highly compact.

The Solid Electrolyte in the present invention comprises: a) a matrix of cross-1 inked polymer chains, having side-chains linked thereto, which side-chains comprise polar groups free from reactive hydrogen atoms, b) a polar aprotic liquid dispersed in the matrix, and c) a highly ionised lithium salt dissolved in the matrix and/or liquid.

In the matrix of the Solid Electrolyte, the cross-linked polymer main chains (to which the side chains are linked) may be for example: essentially organic such as organic polymer chains optionally comprising sulphur, nitrogen, phosphorus or oxygen atoms; or inorganic-organic such as polymer chains comprising silicon and oxygen atoms, for example comprising polymeric polysi loxane £l"ia,Zsa:Land I PATENT 223884 3 - Essentially organic cross-linked polymer main chains are favourably hydrocarbons, or polyethers with cross-linking functions eg oxy or cross-linked -C-C- groups. Preferably such cross-linked sheet chains contain no, or at most a few, free cross-linking eg -C-C- functions.

The cross-lInking eg -C-C- functions are favourably pendent, and may be in the side-chains, e.g. in a terminal position.

However, the electrochromlc device of the present Invention for electrically darkenable windows may as an alternative comprise a matrix which comprises polymer chains without specific cross-linking functions which are cross-linked by C-C bonds between chain atoms in the main chain (and/or in side-chains as defined).

The Solid Electrolyte chains are cross-linked for good mechanical properties, eg tear resistance and to ensure that at a chosen loading of polar liquid the Solid Electrolyte remains solid at ambient temperatures. However, excessive cross-linking tends to affect other desirable physical properties of the Solid Electrolyte adversely, for example extensibility, feasible liquid loading levels and the conductivity of the Solid Electrolyte. The optimum degree of cross-linking will be dictated by a balance of such properties and will vary widely with the spec ific matrix mater iaI (inter alia). Within the composition ranges of the Solid Electrolyte given hereinafter such optimisation is largely a matter of routine trial. However, by way of example it is often suitable if 2 to 8% of the monomer units of the sheet chain backbones are cross-linked, often via functions pendent from such units. In the embodiments of the Solid Electrolyte further described hereinafter, main chains typically average 2,500 to 10,000 backbone units per chain with 50 to 800 cross-links per chain.

Accordingly, in a preferred aspect the present invention provides an electrochromlc device for electrically darkenable windows which comprises a corresponding Solid Electrolyte.

Each chain is favourably linked to an average of at least 2, and preferably at least 4, (for example within such preferred chains 10 to 10,000) side-chains (as hereinbefore defined). ■ ,r—— ——— NtW 2€ALAWi) (followed by page 3A) 16 NOV 1990 - 3A - 223834 The polar groups In such side-chains may for example be ester or ether linkages.

Where the matrix (favourably) consists essentially of cross-linked hydrocarbon, or polyether chains, the side-chains are favourably end-capped polyether or polyether ester, such as polyalkylene oxide, or polyalkylene oxide carbonate side-chains linked to the sheet chains by oxy, or for hydrocarbon and polyether chains, oxycarbonyl or carbonate groups.

By 'end-capped' herein is meant that terminal OH groups in such chains are replaced by groups without active hydrogen atoms, eg ether or ester groups.

In such favoured main and side-chains, the equivalent ratio of side-chain polar groups (excluding any linking groups) to total 223834 i may suitably be in the range 2:3 to 1:6, preferably 2:3 to 1:4, such as 1:2 to 1:3.

Favoured polyether chains with side-chains of the above favoured polyether types may be made for example by copolymerising monomers comprising ethylene and/or propylene oxide with for example a compound selected from butadiene monoxide, glycidyl methacrylate, glycidyl acrylate and vinyl glycidyl ether and in addition with glycidol.

The free -OH groups resulting from the glycidol and the terminal -OH groups of the polyether chains may be reacted with alkylene oxides, preferably ethylene oxide and optionally derivatives thereof, using for example a basic or acidic catalyst to form side-chains comprising polar groups as aforesaid. The free OH groups may be reacted to eliminate the active hydrogen atoms ('capped'), (for example by forming alkoxy groups) by reacting them with an alkyl halide for example methyl chloride in the presence of a basic catalyst or by forming ester groups with a carboxylic acid or anhydride).

Where any of the foregoing cross-linkable polymers contain -C=C- groups (in the main or side chains), they may be cross-linked using for example free radical or Y~radiation, generally after side chain formation and capping (if effected).

Cross-linking may also be achieved even if no unsaturated groups are present, for example, with free radical forming substances for example peroxides, such as benzoyl peroxide, optionally with heating. However, this procedure may cause adhesion of the matrix to a vessel in which it is made, and the degree of cross-linking may be so low that (although corresponding Solid Electrolytes tend to have good ambient temperature conductivities) the mechanical properties (eg tear resistance) of such matrices are impaired, and it is thus generally preferred that cross-linking should take place by reaction of cross- linking functions eg -C=C-groups.

Favoured hydrocarbon main chains may be preformed by polymerisation of moieties containing -C=C- groups. Such polymers are then subsequently or synchronously cross-linked,* optionally via cross-linkable functions (eg further -C=C- functions) favourably pendent from the main chain, including in a side chain as hereinbefore defined eg in a terminal position.

Thus, for example main chains may be formed by polymerisation of a first monomer species comprising a single -C=C- function and a side chain moiety as defined hereinbefore, optionally together with a second monomer comprising two -C=C- functions to provide at least one cross-linkable -C=C- function for the final sheet chain, which is often pendent and often in a side-chain as defined. The side-chain moiety may be a favoured end capped polyether or polyether ester chain. Thus for example the first monomer species may be a methoxy polyethylene oxide methacrylate or acrylate, optionally copolymerised with allyl methacrylate or acrylate as comonomer, or a polyethylene oxide dimethacrylate or diacrylate, or a polyethylene oxide carbonate dimethacrylate or diacrylate, subsequently homopolymeri sed.

End-capping of side-chains (to eliminate active hydrogen atoms) and cross-linking of the main chains may be effected as described above, in the case of cross-linking, whether cross-linking -C=C- groups are present or absent.

The relevant polymerisation of monomer -C=C-groups may be effected using free radical or group transfer initiation or Y~ra<3iation. Such conditions may iWi{eWr(2jffFfCE j 16NWOT0 'j I VEesweo ~ 'I 223884 intrinsically, or may be adjusted to, also effect synchronous or immediately subsequent cross-linking, so that cross-linked matrix formation from monomer may be run as a one-pot process, in particular where a difunctional comonomer is used.

Organic-inorganic polysiloxane chains, (together with the side-chains linked thereto) are preferably of the formula: R R R l i i Si 0 Si 0 Si———0 i i i AAA wherein each group R independently is alkyl or cross-linked alkenyl, (preferably Cx_6 alkyl or cross-linked Cx_6 alkenyl, in particular methyl), or cross-linking oxy, and each group A is a group as defined for R (with the same preferred groups as for R) or a side-chain (as hereinbefore defined) comprising an end-capped polyether or polyether ester, eg a capped polyalkylene oxide or polyalkylene oxide carbonate group, at least 20% and preferably at least 40% of the groups A being such side chains.

Such polysiloxane chains are cross-linked through the groups R when oxy or through -C=C- functions in R and/or A (as defined). Corresponding matrices preferably contain no, or at most few, free -C=C~ functions.

The optimum percentage of groups A which are side-chains as hereinbefore defined will vary widely within the above mentioned ranges with the specific matrix material (inter alia) and is a matter of routine trial to determine. Suitable and typicai^degrees of n cross-linking and main chain lengths for such polysiloxanes are as so described for essentially organic' polymers hereinbefore.

A corresponding matrix may suitably be made by preforming individual chains, complete with all R and A groups as defined, or cross-linkable precursors thereof and subsequently end-capping side-chains if desired as described hereinabefore, and then cross-linking by heating. For R oxy cross-linking functions, corresponding chains, but wherein R is H, are preformed and sufficient water is allowed to be present to provide the desired number of oxy functions. It is preferred that cross-linking should be carried out in an inert atmosphere, for example of nitrogen. Oxygen may be present if desired but tends to accelerate cross-linking and thus produces a "skin" on any surface of the material which is in contact with it.

Where no unsaturation is present free radical transfer initiated cross-linking may be effected as described for organic polymer sheets hereinbefore.

From the foregoing it will be seen in summary that the matrix may be formed inter alia by a) adding the side chains (as defined) to a matrix of corresponding essentially organic cross-linked main chains without side chains, or b) cross-linking a matrix of essentially organic or inorganic-organic polymer chains with side chains (as defined) linked to the polymer chains.

In case b) the initial or product matrix favourably is one which does not readily crystallise at 0 to 100°c. Matrix formation by any of the foregoing methods will generally be effected during production of the Solid Electrolyte as described further hereinafter.

Suitable polar aprotic liquids dispersed in the $ matrix may be any compatible with the rest of the Solid wew-zealand WJreNi*r Office t 16NOV9990 Electrolyte, but include any such liquids with a dielectric constant of at least 20, preferably at least 50 and/or a dipole moment of at least 1.5, preferably at least 3 Debye. The liquid may be a pure liquid or mixture (mutual solution) of liquids or a solution of a solid solute other than the salt component c) as defined hereinbefore of the Solid Electrolyte. Within the above, suitable and preferred liquids are those which comprise or have a component comprising an N0a, CN or (favourably) an -Ax-E-Aa- group where Ax and Aa each independently are a bond, -0-, or -NR- where R is Cx_4 alkyl and E is -CO-, -SO-, -S02~, or -P(0)A3- where A3 independently is as defined for Ax and A2, or -0- when Ax and A, are each a bond. Such liquids or components thereof may also contain other substituents known to increase polarity, but without acidic hydrogen atoms such as secondary amino, esterified carboxyl and, such optionally substitued aminocarbonyl groups.

Within suitable and preferred polar aprotic liquids or components comprising an -Aj-E-Aj- group are those of formula Rj-Aj^-E-Aj-Rj including R^Aj-P (0) (A3-Rj)-Aa-Rj where Rx, R2 and R3 are each independently hydrogen or optionally substituted hydrocarbyl or Rx and R2 together are optionally substituted hydrocarbadiyl (to from a cyclic Rj-A^E-Aj-Rj compound) , for example Cj.jj alkyl optionally non-terminally oxa-substituted, including Cx_4 alkyl, and C2_6 alka-a,w -diyl respectively.

Such liquids or components thereof thus include amides (-CONR-) such as dialkyl formamides for example dimethylformamide and N-methyl pyrrolidone, sulphoxides (-SO-) such as dimethylsulphoxide and thiophene-l-oxide, sulphones (-S02~) such as dimethylsulphone and sulpholane, carbonates (-0-C0-0) such as optionally oxa-substituted dialkyl and alkylene carbonates, for W*iWr<birflftr£ I "NOV WO I BfCClVEO 9 2.? 33 34 example diethyl, dipropyl, and bis(polyalkoxy alkyl) carbonates, including bis(methoxy ethoxyethyl) and bis(methoxy propoxypropyl) carbonates, and ethylene and propylene carbonates.

A group of such liquids include ethylene or propylene carbonate, a dialkyl formamide or -sulphoxide preferably where each alkyl group is Cx_4 alkyl, or a cyclic ether, for example tetrahydrofuran, or higher viscosity liquids such as sulpholane or higher molecular weight congeners of the foregoing, for example bis(polyalkoxyalkyl) carbonates such as bis(methoxyethoxyethyl) carbonate.

Favoured liquids include cyclic amides such as N-methylpyrrolidone, and cyclic carbonates such as propylene carbonate.

The liquid may typically be present in the matrix as 5 "to 250 parts by weight, favourably 35 to 200 parts by weight, per 100 parts by weight of the matrix.

Clearly the matrix should be in practical terms insoluble in the polar aprotic liquid, or, if soluble, the concentration of liquid in the matrix should be insufficient to dissolve the matrix to any appreciable extent. Of course where any salt is insoluble in the matrix the liquid concentration should be sufficient to dissolve the salt adequately. Suitable materials, and concentrations, within these constraints will be evident or a matter of routine trial.

The ions in the ionised lithium salt dissolved in the matrix and/or liquid within the Solid Electrolyte may be, and in the preferred case are, totally discrete and separated or may exist as ion pairs or higher aggregates {eg. triple ions).

Suitable examples of the salt anion including mono- and divalent anions, inter alia I~, SCN", 16NOVWO 223884 r^. o S-sW O ^w' PF6", AsF6", BC14 *, BPht_, alkaryl sulphonate ions, and (preferably) CF3S03", C104" and BF4~. A preferred salt is lithium triflate CF3S03Li. Mixtures of salts may be used.

The salt may typically be present in the matrix in a matrix:salt equivalent weight ratio of 1 equivalent part by weight of salt per 80 to 18,000 parts by weight of matrix, favourably 200 to 18,000, more favourably 200 to 7000 and preferably 400 to 7000 parts by weight.

Where the matrix contains oxygen atoms in the side chains and/or the sheets, these ratios may be expressed in terms of equivalents of matrix oxygen atoms. The salt may be present as 1 equivalent per 4 to 100 equivalents matrix oxygen atoms, favourably per 10 to 40 equivalents.

As is also described and claimed in New Zealand Patent Specification No. 221722, the Solid Electrolyte may be made by a process comprising in any feasible order: a) forming the matrix b) incorporating the highly ionised salt in the matrix or a precursor thereof, and c) introducing the aprotic liquid into the matrix or a precursor thereof.

In the case of an organic or organic-inorganic polymer matrix the steps are preferably carried out in the order b), a) and c) In such case, the salt is incorporated in a material (which may be a non-cross-linked polymer precursor of a cross-linked matrix, or an oligomer or monomer, or a mixture of such species) which is a precursor of a cross-linked polymer matrix. Matrix formation thus involves cross-linking (e.g. as described hereinbefore and optionally polymerisation, either of which may be effected with or without a solvent or vehicle. f aland office 116N0VIWO (*< O O O "> ,4 >}tfo '1 In brief, In such a case, In step b) the salt or a solution thereof Is dissolved in the matrix precursor or a solution thereof, the precursor Is as necessary polymerised, typically to an average of o 2,500 to 10,000 monomer units per main chain backbone, and cross-linked, in step a), as necessary with removal of solvents, to form a solid matrix, and in step c) the aprotlc liquid is introduced.

Step c) may be effected for example by exposing the product to the vapour of the liquid, if necessary under vacuum and/or elevated temperature. For incorporating larger quantities of liquid it may be | necessary to immerse the matrix in the liquid. To prevent leaching or i ! osmosis of the salt from the matrix the liquid should contain more of \ ■ i the salt eg as a 1 or 2 M solution. To prevent Incorporation of | further salt In the matrix the chemical potentials of the salt in the } matrix before dipping and in the solution should be roughly matched, I unless of course it is desired to incorporate further salt In this | way. However, for some salts in some matrices and liquids, higher concentration of the salt may unfavourably decrease the conductivity I of the Solid Electrolyte, possibly by Ion aggregate formation. The js; } optimisation of the conductivity is a matter of ready and routine -> 1 trial as shown for example in the Table (E4.1) to (E4.4) hereinafter, i in an electrochromlc device for electrically darkenable i windows, the Solid Electrolyte as indicated in New Zealand Patent ifi ^ Specification No. 221722 may be of any thickness provided it is 3 cohesive and continuous, and it is clearly advantageous and preferred j that it be as thin as possible. It may typically be from 1000 to 2^ thick, for example 200 to 10yuand 100 to 10^u . As for the electrodes ? referred to hereinafter, at lower thicknesses it will have to be ? applied to a support, ie. an electrode (either of which may in turn be supported), and painting a precursor onto a support and forming the matrix in situ may be desirable.

The pair of electrodes in the electrochromic device may be of j any suitably inert and conductive material eg a metal conventionally ; used in such devices provided that at least one of the electrodes in the pair is a conconventionaI tungsten oxide composite electrode.

WSW^'EALAND ? fWTfeNrOFFICE 16NWNM Mcewa 'A'■?**>• . . cr ^..

,VS. ■• 22:3834 <0 c O Conductive current collectors additional to and In contact with the electrodes will generally be necessary, as Is conventional. Suitable materials with the desired optical properties for use In the electrodes of the device will be icnown to the skilled man, and are described In the prior art referred to hereinbefore.

As is conventional, the electrode other than the tungsten oxide composite electrode ('the other electrode') generally comprises material capable of oxidative electron loss to form a catlonic species. The conventional electrochromlc process of the tungsten oxide composite electrode will be known to the skilled man from the aforementioned prior art. These electrode processes are reversible.

Where the other electrode comprises a cation source, it may suitably comprise an alkali metal such as Na, K or preferably Li. The metal may be comprised as an alloy component for example In a lithium aluminium alloy or less favourably as a dopant in a potentially salifiable ('conductive') polymer in particular one with an extended delocalised electron system, for example poly(p-phenylene) or polyacetylene. In such cases the matrix should not contain any hydrogen atoms reactive to anode metal, for example such atoms n to carbonyloxy groups. Such an alkali metal other electrode is conveniently a thin foil, sheet or plate.

The other electrode must be cohesive and continuous, but it is clearly desirable that it be as thin as possible (provided that the cell does not rely on conduction in the plane of the electrode). The other electrode may typically be from 2,500 to 5 micron thick, for example 250 to 50 micron, it will be appreciated that at lower thicknesses the other electrode will have to be applied to a support, for example a device and/or the electrolyte. It may even be necessary to apply the other electrode to the support eg. by vapour deposition. Such a support may be or comprise a conductive mesh, foil or coating, current collector, equipped with at least one terminal or terminal attachment.

Suitable materials for use in the tungsten oxide composite electrode of the device will be dictated by the desired optical -ZEALAND ^TgNT-OFFICE 16NQVI990 ftteewsb "w properties and wiI I be known to the skilled man, and are described in the prior art referred to hereinbefore. The tungsten oxide composite electrode by definition comprises a so-called tungsten bronze, but may also suitably comprise another higher oxidation state transition metal compound, ie one in which the transition metal is In a higher oxidation stage. Such compounds (set forth In New Zealand Patent SpecificatIon No. 221722) Include transit Ion metal chalcogenides, such as oxides, sulphides and seI en Ides, eg. V205, V6°13' Mo03» Cu0» CuS.

Favoured other compounds Include Vg013 In use Internal current conduction between electrodes takes place via cation (ie. Li+) migration through the Solid Electrolyte.

The composite tungsten oxide electrode must be cohesive and continuous, but It is clearly advantageous and preferred that it be as thin as possible provided that the device does not rely on conduction In the plane of the electrode. The above electrode may typically be from 1,500 to 3 micron thick, for example 150 to 30 micron. It will be appreciated that at the lower thicknesses the above electrode will have to be applied to a support, for example a device wall and/or the electrolyte. It may even be necessary to form the electrode in situ on such a support (matrix formation is described hereinbefore) having eg painted a precursor onto the support. As for the other electrode, such a support may be or comprise a conductive mesh, foil or coating current collector, equipped with at least one terminal or terminal attachment.

The device described above (as with the capacitor or cell assembly described in New Zealand Patent Specification No. 221722) is desirably sealed into an insulative envelope, and preferably a moisture and air impervious one eg a barrier plastic. Where the assembly is in a preferred thin-film embodiment, it may be mounted flat and the cell assembly sandwiched by two thermoplastic films, of for example a polyester such as polyethylene terephthalate, or a NEW ZEALAND PATENT OFFICE il 6 NOV 1990 RECEIVED a polyethersulphone, the edges of which are heat-sealed optional with adhesive to enclose the assembly. This assembly may be further •: enclosed in eg a barrier plastic such as VI clan (ICI). It can also be mounted on a conventional circuit substrate and sealed to the \ substrate by a thermoplastics or thermoset cover. j Suitable methods for fabricating the present device will be t known to the skilled man, and are described in the prior art referred I' to hereinbefore.

The device may be made up by conventional layering/coating techniques. For example, the tungsten oxide composite electrode may I be laid on an insulatlve thermospiastIc sheet or, In particular for | very thin electrodes, a fluid precursor of the electrode, a solution $ f or dispersion of the electrode materials in a suitable vehicle, may | be applied to the sheet, eg using a doctor blade, followed by | any necessary solvent removal/insert Ion and/or curing. The Solid I Electrolyte may then be laid on the electrode, or a fluid precursor I of the Solid Electrolyte may be applied and converted to the Solid •> i Electrolyte. Finally, the other electrode, any current collector I optionally on any insulator layer and the insulator layer itself may | be applied In order. The order of steps may of course be reversed as 1 desired. The Insulator sheets may then be sealed around the edges, | and any further encapsulation carried out. 4 The Solid Electrolyte itself for the devices of the present I invention, and processes for the preparation of the Solid Electrolyte I ?• are Illustrated in following Examples 1 to 7, and the device of the present invention and a method for its fabrication are illustrated in i f following Examples 8 and 9. i The preparation and properties of matrix precursors for the Solid Electrolyte is illustrated in the following Descriptions.

H6N0VNM 223884 - I Q Description 1 Preparation of an Ethylene Oxide (EO)/Methyl Diqol Glycidyl Ether (MDGE)/AIlyI Glycidyl Ether (AGE) Matrix Precursor (UncrossI Inked Terpolymer) (DP Methyl digol glycidyl ether Is of formula /'°\ CH2 - CH - CH2 - 0 - CH2 - CH2 - 0 - CH2 - CH2 - 0 - CK3 A catalyst was made following the technique of E J Vandenberg, Journal of Polymer Science Part A-1 Vol 7 Pages 525-567 (1969) as follows. A 25% solution of EtgAI (Et means ethyl) In heptane was diluted with dry diethyl ether to a concentration of 0.5 moles per litre, cooled to 0°C and water (0.5 mole/mole EtgAI) was added dropwise with stirring over 15 mins. Acetylacetone (0.5 mole/mole Et3AI) was added dropwise with stirring at 0°C. Stirring at 0°C was continued for 15 mins; this was followed by stirring overnight at room temperature all steps being done under an inert nitrogen atmosphere.

The following materials were charged to a stirred nitrogen purged 400 ml stainless steel autoclave; MDGE (19 ml), AGE (4 ml), and toluene (200 ml).

Qflta luef ao ahnt/a Mft mil anH athu lonA rtv S Ha ( 1 flm I ae a 16 liquid) were then added whilst continuing to stir throughout and the temperature raised to 110°C for 2 hours. The hot viscous polymer solution produced was discharged into a 1 litre jar containing 5 ml methanol to inactivate the catalyst. The autoclave was given two hot washes with a total of 500 ml toluene. The washings were bulked with the polymer solution and thoroughly mixed.

The polymer solution was rotary evaporated to a volume of 300 ml and cast in a polyester tray in a fume cupboard and left overnight for the solvent to evaporate. The terpolymer was finally dried in a vacuum oven at 80° overnight to give 18.4 g of a sticky, rubbery product.

Molecular wt of the product was measured by gel permeation chromatography using lithium bromide in dimethylformamide as solvent.

MW = 380,000 100 MHz NMR was used to measure the relative amounts of the three monomers incorporated in the final terpolymer which were:- (Uncrosslinked Polymer) ,-Measurement of Conductivity of Uncrosslinked Film 1 g of terpolymer (Dl) was dissolved in 25 ml dry acetonitrile with stirring under a nitrogen atmosphere. Lithium triflate (CF3S03Li) was added to the solution to give a ratio of 16:1 oxygen atoms present in the polymer to lithium atoms. 77.9 mole % EO 17.5 mole % MDGE 4.6 mole % AGE Example 1 i) Incorporation of Salt in Matrix Precursor 1«NWI9» The solution was cast into a glass/polytetra fluoroethylene mould and the solvent allowed to evaporate slowly under a stream of nitrogen. The 200 yw film was dried at 80° under vacuum for 4 hours to remove any traces of water or solvent and its ionic conductivity over a range of temperatures was measured by standard AC impedance techniques.

Conductivity 20°C = 2 x 10"5 mho.cm ii) Incorporation of Salt in Matrix Precursor (Uncrosslinked Polymer); Forming the Matrix by Cross-linking the Precursor a) 1 g of terpolymer (Dl) was dissolved in 25 ml acetonitrile with stirring and lithium triflate was added to give a 16:1 oxygen to lithium ratio. 1.0 wt % dry benzoyl peroxide was added to the solution which was cast as above into a 200 pm film under a stream of nitrogen.

The film was lightly cross-linked by heating in a vacuum oven at 110°C for 30 minutes.

Conductivity 20°C = 3.5 x 10"6 mho.cm _1 b) An acetonitrile solution of terpolymer (Dl) (85% w/w). lithium triflate (13% w/w) and benzoyl peroxide (2% w/w), was cast into a film, and the film was cured, as in a) above to give a 50 pm thick film. iii) Introducing the Liquid into the Matrix; adding Propylene Carbonate (PC) Dry propylene carbonate was placed in the bottom of a dessicator and molecular sieve added to it. The dried cross-linked film from ii)a) above was placed in the vapour space above the liquid for an appropriate time at a total pressure of 1 to 2 mm of mercury at room temperature. In general about 25% of the propylene carbonate is taken up per hour based on the weightWfeKfzEALAND fawent'office I16N0VIW0 c O *"> 'i r> 0 4 .t .< o 6 <1 /""s W' O ^HSJr the polymer and this rate is essentially constant for at least four hours. Solid Electrolytes (El.l) to (El.3) were produced in this way.

The procedure was repeated using the following liquids to produce the following Solid Electrolytes: Sulpholane (El.4) and (El.5) Methyl digol carbonate (El.6) and (El.7) N-methylpyrrolidone (El.8) and (El.9), all listed in the Table hereinafter.

The dried cross-linked film from ii) b) above was similarly treated with PC to a 50% weight increase to give Solid Electrolyte (El.10).

All these Solid Electrolyte films were easy to 15 handle and adequately dimensionally stable.

The films were kept dry before use in a cell.

Description 2 i) Preparation of a Methoxypolyethoxyethyl Methacrylate (MPM) Matrix Precursor (Monomer) (D2.1) Methoxy PEG 350, Me(OCH2CHa),.5-0H (145.8 g; dried over 4A molecular sieve), HPLC grade methylene chloride (80 ml) and dimethylaminopyridine (4.24 g) were added to a 500 ml flask with mechanical stirring. The 25 flask was immersed in a cold water bath and methacrylic anhydride (65.0 g of 94% purity) added over 30 minutes from a dropping funnel. The reaction mixture was stirred for 17 hours at room temperature. The solution was transferred to a separating funnel and washed with 2 x 30 200 ml dilute HC1 (40 ml conc. HC1 in 360 ml water) followed by 2 x 200 ml 10% sodium bicarbonate solution followed by 2 x 200 ml water.

The solution was dried over MgS04.lH20 and filtered. Irganox 1010 antioxidant (0.5 g) was added and 25AIANO 1 16NOVI990 223834 the solution rotary evaporated and then pumped for 2.5 hours on the vac line with stirring.

Finally, the MPM was distilled on a short path still under vacuum (5 x 10"1 mbar) at 230°C. Yield 115 g, stored in the freezer until required. ii) Preparation of an MPM/Allyl Methacrylate (AM) Matrix Precursor (Uncrosslinked Copolymer) (D2.2) AM (ex Aldrich) was distilled under vacuum before use and passed down a column of 4A molecular sieve to remove the last traces of water. 1-Methoxy-l-methyl-siloxy-2-methylprop-l-ene (MTS) (Aldrich) was distilled before use and stored in PTFE containers in the refrigerator. Tetrabutylammonium fluoride (TBAF) (Aldrich) supplied as a 1M THF solution was stood over CaH2 for 2 days and filtered before use.

All operations were done under nitrogen in flame dried glass apparatus.

To a stirred solution of MTS (5.5 x 10~3 g) in dry THF (10.0 ml) was added (D2.1) (3.0 g), AM (0.11 ml) and TBAF (2 pi of 1M THF solution). The mixture warmed up and was stirred overnight at room temperature. 50 ppm Irganox 1010 antioxidant was added to the very viscous clear solution, which was cast into a polyester tray in a stream of nitrogen. The last traces of THF were removed by heating in a vacuum oven at 60° for 4 hours.

Molecular wt of the product was measured by gel permeation chromatography using lithium bromide in dimethylformamide as solvent MW = 113,000 100 MHz NMR in CDC13 was recorded. There were virtually no free monomers in the copolymer and the ratio of MP 350 M units to AM units was 9:1.

PATW©fffi|£E Example 2 i) Incorporation of Salt in Matrix Precursor (Uncrossllnked Copolymer); Forming the Matrix by Crosslinking the Precursor Copolymer (D2.2) (1 g) was dissolved in 25 ml acetonitrile with stirring and lithium triflate was added to give a 16:1 oxygen to lithium ratio. 1.0 wt % dry benzoyl peroxide was added to the solution which was cast as in description 2 ii) into a 200 ym film under a stream of nitrogen. The film was cross-linked by heating in a vacuum oven at 110°C for 30 minutes.

Conductivity = 3.25 x 10*6 mho cm*1 (determined as in Example 7). ii) Introducing the Liquid into the Matrix; Addition of PC- As in Example l(iii) with a similar rate of uptake to give Solid Electrolytes (E2.1) to (E2.3), all listed in the Table hereinafter.

Description 3 Preparation of an EO/MDGE Matrix Precursor (Uncrosslinked Copolymer) (D3) As in Description 1, but omitting AGE and using 22 ml MDGE.

Yield 15 g; M Wt 431,000; Mole % MDGE 31.3.

Example 3 i) Incorporation of Salt in Matrix Precursor (Uncrosslinked Copolymer); Forming the Matrix by Crosslinking the Precursor Mixture Copolymer (D3) (1.062 g) and dry benzoyl peroxide (0.0244 g) were dissolved in 25 ml acetonitrile, with stirring and lithium triflate was added to give a 16:1 oxygen to lithium ratio. The solution was cast as in new zealand PATENT OFFICE 16N0V1990 ^ RECEIVED a 'r>.

Vyv-"' gr>y«/ u O O 'i <"•, ^ * GO 'J Example 2 into a 200 ym film under a stream of nitrogen. The film was cross-linked by heating in a vacuum oven at 110°C for 4 hours. Cross-linked films produced in this way were very difficult to remove from the mould.

If the mould is immersed in liquid nitrogen, then the film usually separates cleanly. The films were re-dried by heating in a vacuum oven at 80°C for 3 hours.

Conductivity of cross-linked copolymer film = 6 x 10 10"6 mho cm-1 at 20°C (determined as in Example 7). ii) Introducing the Liquid into the Matrix; Addition of PC As in Example 1 (iii) to give Solid Electrolytes (E3.1) to (E3.3) all listed in the Table hereinafter.

Description 4 Preparation of a Methacrylate End-capped Poly(ethylene Ether Carbonate) (Methacryloxy-poly (ethoxycarbonyloxyethoxy)ethyl Methacrylate) Matrix 20 Precursor (Monomer) (D4) Diethylene glycol (27.7 g) and dibutyl carbonate (44.5 g) were weighed into a test-tube fitted with a side arm and held under nitrogen. Sodium ethoxide solution (1 ml of 1.02 molar solution) was added by 25 syringe. The reaction mixture was stirred magnetically. The tube was immersed in an oil bath at 150°C. The temperature was raised to 200°C over 1 hour at atmospheric pressure. The pressure in the apparatus was gradually lowered to a few mm of Hg over 3 hours, to 30 distil off butanol essentially completely.

After cooling, the very viscous product resin was dissolved in chloroform (100 ml) and washed in a separating funnel with dilute HC1 (10 ml conc HC1/40 ml water) and then water (3 x 60 ml).

Wl-\A/ ZEALAND I LATENT OFFICE i!6NOVI990 deceived c 99 3884 n The solution was rotary evaporated and the resin dried under vacuum at 180°C for 2 hours.

Molecular weight was determined by VPO in methyl benzoate at 136°C and found to be 1810 ± 10%. 5 Dimethylaminopyridine (0.1 g) was added to this product hydroxyl terminated oligomer (5 g) followed by methacrylic anhydride (2.17 g; Aldrich, 94% pure) in a reaction flask blanketed with nitrogen. The reaction mixture was stirred magnetically at 80°C for 3 hours. 10 The excess methacrylic anhydride was distilled out under vacuum at 80°C. The resin was dissolved in methylene chloride and transferred to a separating funnel and washed once with dilute HCl and then three times with water. The solution was dried with MgS04.lHa0 and 15 filtered. 200 ppm 4-methoxyphenol antioxidant was added and the solution rotary evaporated until most of the methylene chloride had come off. The last of the methylene chloride was removed in a dry air stream over 4 hours.

Example 4 i) Incorporation of Salt in Matrix Precursor (Monomer); Forming the Matrix by Polymerising and Cross-linking the Precursor Mixture 25 A casting solution was prepared from resin (D4) (2.357 g), lithium triflate (0.3749 g), and dry benzoyl peroxide (0.046 g) in HPLC grade acetonitrile (20 ml) with stirring under nitrogen. 2 ml of this solution was placed in a glass mould 30 coated with a mould release agent. The mould was placed in an oven with nitrogen blowing through it. The temperature was raised to 110°C at 2°C/minute, held at 110°C for 2 hours and slow cooled to room temperature overnight. office 16HOVI990 The clear rubbery film could be pulled easily from the mould.

Conductivity at 20°C = 1.3 x 10"9 mho cm-1 (determined as in Example 7) . ii) Introducing the Liquid into the Matrix; Addition of PC As in Example l(iii) to give Solid Electrolyte (E4.1) listed in the Table hereinafter.

It proved difficult to incorporate any further propylene carbonate into the film by this method. An alternative method was to suspend the film in a dry solution of lithium triflate in propylene carbonate (1 molar). The film was dried by pressing between filter papers. This procedure was in a dry box, to give Solid Electrolyte (E4.2) listed in the Table hereinafter.

Example 5 i) One-pot Preparation of an MPM/Polyethylene Glycol Dimethacrylate (PPM) Matrix (Cross-linked Polymer) including Salt Polyethylene glycol 4 00 dimethacrylate (0.05 g; Polysciences), MPM (D2.1) (2.0 g) and dry benzoyl peroxide (0.02 g) were co-dissolved in 20 ml HPLC grade acetonitrile. Lithium triflate was added to the solution to give a ratio of 16:1 oxygen atoms present in the oligomers to lithium atoms. 2 ml of this solution was cast and cured as in Example 4, but at 80°C for 24 hr. ii) Introducing the Liquid into the Matrix; Addition of PC As in Example l(iii) to give Solid Electrolytes (E5.1) to (E5.4), all listed in the Table hereinafter. 223884 n- Description 6 Preparation of a Polysiloxane Matrix Precursor (Uncrosslinked Copolymer) (D6) A silicon compound of formula CH j CH, i CH, - Si - i CH 3 H H CH, H ll I I 0 - Si-O-Si -O-Si-O-Si- i CHj CH3 CH, CH3 CH, l 3 0 - Si - CH, I CH3 48 (4 g) and a compound of formula 10 CHj CH, = CH CHaO (CjH40)9.5 CH3 (6 g) were dissolved in dry toluene (10 ml) and 1.0 ml of a solution of trans PtCl3I(CaHs)2S]s (1 mg dissolved in 1 ml of toluene) added.

This mixture was refluxed under Na for 2.5 hours, 15 to give a fairly viscous solution. The toluene was removed under vacuum to give a very viscous copolymer (D.5).

C O Example 6 i) Incorporation of Salt into Matrix Precursor (Uncross-linked Copolymer) 6.218 g of copolymer (D6) and 0.6223 g lithium triflate (0.6223 g) (0:Li ratio = 20:1) were co-dissolved in 5 ml acetonitrile with stirring. 5 ml dioxane was added to reduce the evaporation of acetonitrile. The solution was cast onto the stainless steel electrodes of conductivity cells and solvent allowed to evaporate for 1 hour in air. ii) Forming the Matrix by Cross-linking the Precursor Copolymer coated electrodes were ciire^d in air and "'f A r £, argon as described below, t<' V E O. c 223834 Air 0 The electrodes were heated rapidly to 140°C and held at 140°C for 20 minutes in an oven and immediately removed from the oven.

Conductivity was 5.2 x 10"® mho cm-1 (determined as in Example 7).

Film thickness was 170 pun.

Argon Films were cast under argon and placed in an argon flushed oven. The oven was heated to 60° for 25 minutes and slowly allowed to cool to room temperature overnight. iii) Introducing the Liquid into the Matrix; Addition of PC PC was incorporated into the 'air' films above, as in Example l(iii), whilst still attached to the electrodes, to give Solid Electrolytes (E6.1) to (E6.3), all listed in the Table hereinafter.

Example 7 Measurement of Conductivity of the Solid Electrolyte The ionic conductivity of the foregoing Solid Electrolyte films was measured by standard AC impedance techniques using a Solartron 1250 frequency response analyser. The results are shown in the following Table, in which the '% liquid1 is the weight % of liquid in the Solid Electrolyte, '% Increase* is the number of parts by weight liquid taken up by the penultimate film in the final process step taken as 100 parts, and conductivities are at 20°C unless otherwise indicated in or by following brackets. '6 NOV W0 TABLE Solid Electrolyte % Liquid % Increase Conductivity mho.cm-1 x 104 (El.1) 16.7 1.6 (25) (El.2) 28. 6 40 3.0 (25) (El.3) 37. 5 60 .4 (25) (El.4) 33.2 47 0.52 (El.5) 49. 3 96 0.96 (El.6) 13. 0 0.17 (El.7) 44.4 80 0.39 (El.8) 41.2 71 1.55 (El.9) 60 150 4.8 (E2.1) 16.7 1.1 (E2.2) 28. 6 40 2.15 (E2.3) 37. 5 60 3.6 (E3.1) 18 1.3 (E3.2) 1.8 (E3.3) 33. 3 50 3.6 (E4.1) 33. 3 50 0.23 (E4.2) 80 1.2 (E4.3) 140 2.0 (E4.5) 180 0.48 (E5.1) 28.8 40 2.3 (E5.2) 33. 3 50 3.2 (E5.3) 37. 5 60 4.0 (E5.4) 41. 2 70 .2 (E6.1) 16.7 1.0 (E6.2) 28. 6 40 2.3 * * (E6.3) 40. 0 66 6.0 * % increase may include added salt * Determined as in Example 6 223884 Example 8 An Electrochromlc Device Assembly Comprising the Solid Electrolyte The assembly of a device in accordance with the present invention is described below with reference to the accompanying drawings (not to scale) in which: Figure 1 is a side elevation of the device assembly.

Figure 2 is a plan section of the assembly viewed along AA in Figures 1 and 3.

Figure 3 Is a cross section of the device assembly viewed along BB In Figure 1, The film 1 of Solid Electrolyte (El.10) prepared In Example 1ii)b) Is sandwiched between and bore reslilently against a coterminous layer 2 of tungsten oxide composite cathode and a coterminous other electrode (the layer, film and other electrode O being mutually In register) to produce a device 4, 600 mm in plan area.

The device 4 was heat-sealed between two sheets 5 of polyester (Meiinex; ICI), each coated, on the face so biased into electrical contact with each of the device electrodes with a current collector from each electrode.

The sheets 5 are of the same planar dimensions although larger than the device 4 in plan and are sealed around the device 4 with only their long edges in register, to form end lugs 7 with metal faces 8. Sealing is effected around the edges of the device 4 with a layer 9 of adhesive. The sealed device (excluding most of the lugs 7) is coated with a layer 10 of an air and water impervious barrier polymer. The projecting lugs 7 are used for external connections to the device, and may if desired be fitted with appropriate terminals. The resulting device assembly is less than 1 mm thick.

Example 9 Further Cell Assemblies comprising the Solid Electrolyte Afl the Solid Electrolytes in the Table may be used to form assemblies analogously to that of Example 8. —r^~- NEW zealand PATENT office 116N0V199C w RECEIVED 22 ="<834

Claims (6)

WHAT WE CLAIM IS:

1. An electrochromlc device for electrically darkenable windows comprising a pair of electrodes, at least one of which is a tungsten oxide composite electrode, separated by a solid electrolyte, which compr ises: a) a matrix of cross-linked polymer chains having side-chains linked thereto, which side-chains comprise polar groups free from reactive hydrogen atoms, b) a polar aprotic liquid dispersed in the matrix, and c) a highly ionised lithium salt dissolved in the matrix and/or liquid.

2. A device according to claim 1 wherein the aprotic polar liquid Is one with a dielectric constant of at least SO and/or a dipole moment of'at least 3 Debye.

3. A device according to claim 2 wherein the aprotic polar liquid is ethylene or propylene carbonate, a dialkylformamide or -sulphoxlde, a cyclic ether, sulpholane or a bis(poIyaIkoxyaIkyI) carbonate, or a cyclic amide.

4. A device according to claim 1, wherein the liquid is present in the matrix at 35 to 200 parts by weight per 100 parts by weight of the matr i x.

5. A device according to claim 1 wherein the matrix is a derivative of a polyalkylene oxide.

6. An electrochromlc device as defined in claim 1 substantially as herein described with reference to any example thereof. Al___ _ . .1 Bis/Their authorised Agent •\. FV f.K £ SON NEW ZEALAND _ PATENT OFFICE | 116 NOV 1990 RECEIVED