Energy storage device and ionic conducting composition for use therein

Abstract

The present invention relates to an energy storage device comprising a silicate comprises a formula:
M.sub.vM1.sub.wM2.sub.xSi.sub.yO.sub.z
where M is selected from the group consisting of Li, Na, K, Al, and Mg M1 is selected from the group consisting of alkaline metals, alkaline earth metals, Ti, Mn, Fe, La, Zr, Ce, Ta, Nb, V and combinations thereof; M2 is selected from the group consisting of B, Al, Ga, Ge or combinations thereof; v, y and z are greater than 0; w and/or x is greater than 0; y≥x; and wherein M.sub.vM1.sub.wM2.sub.xSi.sub.yO.sub.z accounts for at least 90 wt % of the composition.

Claims

1. A lithium energy storage device comprising: a glass or a glass ceramic silicate composition comprising: 1 to 30 wt % Li.sub.2O; 10 to 60 wt % ZrO.sub.2; and 20 to 80 wt % SiO.sub.2, wherein the sum of Li.sub.2O+ZrO.sub.2+SiO.sub.2 is greater than 50 wt %, the silicate composition further including oxides selected from the group consisting of alkaline earth metal oxides, boron oxide, tantalum oxide, gallium oxide, potassium oxide, germanium oxide, lanthanum oxide, vanadium oxide, manganese oxide, iron oxide, cerium oxide, niobium oxide, titanium oxide and combinations thereof, and there is a sum of the oxides+Li.sub.2O+ZrO.sub.2+SiO.sub.2 that is at least 95 wt %, wherein the silicate composition forms part of a lithium ion conductive electrolyte, a separator and/or an electrode.

2. The device according to claim 1, wherein in the glass or glass ceramic silicate composition there is a combined amount of Al.sub.2O.sub.3 and TiO.sub.2 between 0.5 wt % and 30 wt % and the amount of Li2O is between 0.5 wt % and 15 wt %.

3. The device according to claim 1, wherein in the glass or glass ceramic silicate composition is in the form of a nanowire or a fibre.

4. The device according to claim 1, wherein in the glass or glass ceramic silicate composition there is less than 1.0 wt % phosphorus oxide.

5. The device according to claim 1, wherein in the glass or glass ceramic silicate composition there is: 4 to 12 wt % Li.sub.2O; 15 to 55 wt % ZrO.sub.2; 50 to 75 wt % SiO.sub.2; and 0 to 30 wt % other components selected from the group consisting of alkaline earth metal oxide, boron oxide, tantalum oxide, gallium oxide, potassium oxide, germanium oxide, lanthanum oxide, vanadium oxide, manganese oxide, iron oxide, cerium oxide, niobium oxide, titanium oxide and combinations thereof.

6. The device according to claim 1, wherein there is in the glass or glass ceramic silicate composition 3 to 15 wt % Li.sub.2O.

7. The device according to claim 1, wherein there is in the glass or glass ceramic silicate composition less than 18 wt % Li.sub.2O.

8. The device according to claim 1, wherein there is in the glass or glass ceramic silicate composition: 0 to 80 wt % silicate composition fibres; 0 to 80 wt % silicate composition particles; and 20 to 98 wt % lithium ion conducting organic electrolyte.

9. The device according to claim 1, wherein the lithium ion conducting organic electrolyte comprises an electrolytic salt dissolved or dispersed in an electrolytic medium.

10. The device according to claim 1, wherein the electrolytic medium comprises a polymer.

11. The device of claim 1, wherein in the glass or a glass ceramic silicate composition there is a sum of Li.sub.2O+ZrO.sub.2+SiO.sub.2 greater than 80 wt %.

12. A lithium energy storage device comprising: a glass or a glass ceramic silicate composition comprising: 1 to 30 wt % Li.sub.2O; 10 to 60 wt % ZrO.sub.2; and 20 to 80 wt % SiO.sub.2, wherein the sum of Li.sub.2O+ZrO.sub.2+SiO.sub.2 is greater than 50 wt %, the silicate composition further including oxides selected from the group consisting of alkaline earth metal oxides, boron oxide, tantalum oxide, gallium oxide, germanium oxide, lanthanum oxide, vanadium oxide, manganese oxide, iron oxide, cerium oxide, niobium oxide and combinations thereof, and there is a sum of the oxides +Li.sub.2O+ZrO.sub.2+SiO.sub.2 that is at least 98 wt %, wherein the silicate composition forms part of a lithium ion conductive electrolyte, a separator and/or an electrode.

13. The device of claim 12, wherein in the glass or a glass ceramic silicate composition there is a sum of Li.sub.2O+ZrO.sub.2+SiO.sub.2 greater than 80 wt %.

14. The device according to claim 12, wherein in the glass or a glass ceramic silicate composition there is 3 to 15 wt % Li.sub.2O.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a XRD diagram for Sample 1, after being fired at 1000° C.

(2) FIG. 2 is a XRD diagram for Sample 2, after being fired at 1000° C.;

(3) FIG. 3 is a XRD diagram for Sample 4a after heat treatment at various temperatures.

(4) FIG. 4 is a SEM image of Sample 4a.

DETAILED DESCRIPTION

(5) The silicate compositions of the present invention preferably form part or all of a separator or part or all of solid electrolyte or part of an inorganic/organic electrolyte matrix (e.g. polymer composite within a lithium ion energy storage device, such as a battery or capacitor).

(6) The silicate composition of the present invention may be in any form (e.g. fibre, particle and/or film) and manufactured via any suitable means and ground or milled to the desired particle size distribution. When formed as a particle, the mean particle size will vary with application, but is preferably between 1 nm and 100 μm and more preferably between 10 nm and 5 μm.

(7) Energy Storage Device Components

(8) The chemically and thermally inert nature of the silicate compositions enable them to be compatible to most battery systems.

(9) Separator

(10) In one embodiment, lithium zirconium silicate fibres (and/or particles) of the present invention are integrated into a separator (or inorganic-organic hybrid membrane). The fibres preferably form a non-woven web from which the separator is produced. In one embodiment the fibres are substantially orientated in the same plane as the web, such that within a battery the fibres are substantially parallel to the electrodes. In other embodiments, the fibres are randomly oriented.

(11) In one embodiment, the configuration silicate fibres form a tortuous lithium ion pathway from the anode side of the separator to the cathode side. Preferably the silicate fibres contact one or more adjacent fibres within the separator to form a plurality of lithium ion pathways. The separators preferably also comprise lithium ion conducting inorganic fillers. The fillers may be used to control the separator porosity in addition to creating a plurality of continuous ionic conductive pathways. Despite the tortuous pathways that the fibres produce, connection between fibres and inorganic particles enable lithium ion transfer bridges to be formed between fibres and particles thereby enabling more direct lithium ion transfer across the separator.

(12) In a preferred embodiment, two or more inorganic fibres and/or inorganic particles form a lithium ion conductive pathway across the separator (inorganic-organic hybrid membrane).

(13) The composition of the separator (hybrid membrane) preferably comprises in the range of: 2 to 100 wt % or 5 to 100 wt %, more preferably 30 to 98 wt %, even more preferably 40 to 95 wt %, yet even more preferably 50 to 90 wt %, yet even more preferably 60 and 80 wt % silicate fibres; 0 to 95 wt % or 1 to 90 wt %, more preferably 5 to 60 wt %, even more preferably 10 to 50 wt %, yet even more preferably 15 to 40 wt % and most preferably 20 and 40 wt % inorganic particles, preferably silicate particles; and 0 to 90 wt % or 0 to 50 wt %; more preferably 3 to 20 wt % and even more preferably 5 to 10 wt % binder

(14) In a preferred embodiment, the fibre content is between 2 wt % and 10 wt % (e.g. separator comprising silicate fibres and PEO or PAN).

(15) In one embodiment the composition of the silicate fibres are the same as the composition of the silicate inorganic particles. For the purposes of the present invention, the “same composition” means specific oxide components are within 1 wt % or 10 wt % of each other, whichever is greater.

(16) The inorganic particles preferably have a mean diameter of less than 100 microns and more preferably less than 50 microns, yet even more preferably less than 20 microns and more preferably less than 10 microns. The mean diameter of the particles is typically at least 10 nm and more preferably at least 100 nm. A smaller particle size enables the separators to be thinner and increases the ionic conductive surface area of the separator.

(17) The binder may be inorganic or organic. The inorganic binders preferably have a softening temperature below the softening temperature of the inorganic fibres. In some embodiments, the inorganic binder is a lithium ion conducting particle.

(18) Suitable organic binders may be selected from the group consisting of but not limited to polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), Polyphenylene sulphide (PSS), polyethylene oxide (PEO), polyacrylonitrile (PAN), polytetrafluoroethylene, polyacrylate, styrene-butadiene rubber, polylactic acid, polyvinyl alcohol, polyacrylonitrile, poly(methyl methacrylate) and polysaccharides (for example carboxymethylcellulose (CMC)), and mixtures and copolymers thereof.

(19) In one embodiment, the organic binders are preferably polymers having a relatively high melting temperature (e.g. preferably >150° C. and more preferably greater than 200° C.) to enable the separator still effectively to function at elevated temperatures.

(20) The separator preferably forms a composite membrane (or matrix) with a solid, gel or liquid electrolyte.

(21) The ceramic fibre separator may be prepared by a traditional wet winding process. The lithium ion conducting fibres, were combined with a binder (for example carboxymethyl cellulose (CMC)) and a dispersant (for example polyethylene oxide (PEO)) added. The proportion of the materials (e.g. weight ratio of 90:7:3 respectively) may be dissolved into an amount of distilled water or organic solvent under a continuous stir, whereas the viscosity of the solution may be controlled by the binder contents. Following stirring for 8 h, the mixed solution may be placed onto the forming wire to form a membrane, followed by overnight drying at 120° C. under vacuum. Consequently, the membrane thickness was controlled by an extended roller.

(22) Alternatively, the separator may be made in accordance with the general methodology disclosed in U.S. Pat. No. 9,637,861, with the exception that the inorganic fibres of the present invention partially and preferably completely replace microfibers. Additionally, the nanofibers can be partially or completely replaced with fillers and/or binders. Fillers and/or binders are preferably added to control the porosity of the separator. The fillers and binders may also increase the surface area of lithium ion conductive pathways. In one embodiment, organic binders are used to bind lithium ion conductive particles within a non-woven fibrous web.

(23) The resultant separators preferably exhibit one or more of the following characteristics: porosity ranging from about 70% to about 98%; peel strength from about 0.03 kN m.sup.−1 to about 0.50 kN m.sup.−1; an ASTM Gurley Number in the range of about 30 to 150 sec. ASTM Gurley Number refers to the time it takes for 10 cc of air at 12.2 inches of water to pass through one square inch of membrane; a liquid absorbency ranging from about 200% to about 1300%. an areal density ranging from about 0.2 g m.sup.−2 to about 3 g m.sup.−2. A thickness of less than 100 μm preferably less than 50 μm and more preferably less than 30 μm.
Polymer Component

(24) In some embodiments, the separator or hybrid membrane preferably comprises a polymer component. The polymer component may function to assist in the formation of the separator (e.g. action as a binder of the inorganic fibres) and/or enhance the properties of the separator (e.g. toughness and/or enhance porosity).

(25) To avoid the polymer component negatively affecting the functioning of the separator (e.g. safety or conductivity), the proportion of the polymer component is preferably in the range of 0.1 wt % to 50 wt %, more preferably 2 wt % to 40 wt % and even more preferably 5 wt % and 25 wt %. In preferred embodiments, the polymer content is less than 20 wt %, more preferably less than 10 wt % and yet even more preferably less than 5 wt %.

(26) In embodiments in which the inorganic fibres or particles form part of a polymer based separator or solid (i.e. polymer) electrolyte, the proportion of polymer (or polymer/lithium ion salts) is preferably at least 60 wt %, more preferably at least 80 wt % and even more preferably at least 85 wt % and yet even more preferably at least 90 wt % of the total of the separator or solid electrolyte. In this embodiment, the silicate composition fibres or particles serve to enhance the mechanical and conductive properties of the polymer.

(27) The polymer may comprise polyvinylidene fluoride (PVDF), poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)), Polyphenylene sulphide (PPS), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyimide (PI), polyvinyl pyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polylactic acid (PLA), polysaccharides (for example carboxymethyl cellulose (CMC)), styrene-butadiene rubber (SBR) and combinations thereof.

(28) In one embodiment, the polymer component forms part of a hybrid organic/inorganic fibre, preferably produced via electro-spinning techniques, such as those disclosed in U.S. Pat. No. 8,846,199.

(29) Electrolyte

(30) The silicate composition of the present invention preferably forms part of a lithium ion conductive electrolyte (including a solid, liquid or gel electrolyte). The electrolyte is preferably a non-aqueous solvent, polymer or gel having an electrolytic salt dissolved or dispersed therein to form an electrolytic medium. The non-aqueous electrolytic medium of the present invention is not particularly limited as long as the electrolyte salt can be dissolved or dispersed in it, and for example may be any one of many publicly known electrolytic mediums used for energy storage devices.

(31) Polymer Based

(32) In one embodiment, the silicate composition forms a matrix with a lithium ion conducting organic electrolyte, such as Solid Polymer Electrolytes (SPE). SPEs may include amorphous or semi-crystalline PEO, PPS, PAN, polyvinyl chloride (PVC), PVDF, PMMA, poly(vinylidene fluoride-hexafluoro propylene) P(VDF-HFP), PVA, PLA, PVP and combinations thereof. The polymers may be selected from ionically (e.g. lithium ion) conductive polymers such as polyethers, polysaccharides, polyacrylates, polyamines, polyimides, polyamides and other polar groups including heteroatom systems.

(33) In a preferred embodiment the SPE comprises PEO, PAN or PPS. Suitable crystalline SPE include 6PEO:LiAF.sub.6 where A is P, As or Sb.

(34) When the above-mentioned polymers or polymer gels are used as a medium to dissociate the electrolyte salt, one of the following methods may be used. That is, a method in which a solution obtained by dissolving an electrolyte salt in a non-aqueous liquid solvent is added dropwise to a polymer formed into a film by a publicly known method to impregnate the polymer with the electrolyte salt (e.g. lithium salt) and the non-aqueous solvent or to support the electrolyte salt and the non-aqueous solvent; a method in which a polymer and an electrolyte salt are melted at a temperature of a melting point of the polymer or higher, mixed, and then formed into a film, and the film is impregnated with a non-aqueous solvent (these are gel electrolytes); a method in which a non-aqueous electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent in advance is mixed with a polymer, and the resulting mixture is formed into a film by a casting method or a coating method, and an organic solvent is volatilized; and a method in which a polymer and an electrolyte salt are melted at a temperature of a melting point of the polymer or higher, mixed, and then molded (intrinsic polymer electrolyte) may be used to obtain the film.

(35) Inorganic Based

(36) In an alternative embodiment, the silicate composition forms a matrix with a Composite Solid Electrolyte (CSE). CSEs may include SPE and non-Li based materials such as TiO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, Metal Organic Frameworks (MOF's), CNT's, graphene.

(37) Alternatively, the solid electrolyte may consist of the silicate composition.

(38) Liquid Based

(39) Non-aqueous solvents such as cyclic carbonates described later and a solvent other than a cyclic carbonate; and a medium such as a polymer or a polymer gel which is used in place of the solvent, can be used.

(40) As the non-aqueous solvent, it is preferred that such a solvent exhibits high dielectric constant, can readily dissolve an electrolyte salt, has a boiling point of not less than 60° C., and is electrochemically stable during operation of the energy storage device. The non-aqueous solvent is more preferably an organic solvent of which water content is small. Such an organic solvent is exemplified by an ether solvent such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane and 1,3-dioxolan; a chain carbonate ester solvent such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate and methyl phenyl carbonate; a saturated cyclic carbonate solvent such as ethylene carbonate, propylene carbonate, 2,3-dimethylethylene carbonate (i.e. 2,3-butanediyl carbonate), 1,2-butylene carbonate and erythritan carbonate; a cyclic carbonate solvent having an unsaturated bond, such as vinylene carbonate, methylvinylene carbonate (MVC; i.e., 4-methyl-1,3-dioxole-2-one), ethylvinylene carbonate (EVC; i.e., 4-ethyl-1,3-dioxole-2-one), 2-vinylethylene carbonate (i.e., 4-vinyl-1,3-dioxolane-2-one) and phenylethylene carbonate (i.e., 4-phenyl-1,3-dioxolane-2-one); a fluorine-containing cyclic carbonate solvent such as fluoroethylene carbonate, 4,5-difluoroethylene carbonate and trifluoropropylene carbonate; an aromatic carboxylate ester solvent such as methyl benzoate and ethyl benzoate; a lactone solvent such as .gamma.-butyrolactone, .gamma.-valerolactone and .delta.-valerolactone; a phosphate ester solvent such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate and triethyl phosphate; a nitrile solvent such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile and isobutyronitrile; a sulfur compound solvent such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methylsulfolane and 2,4-dimethylsulfolane; an aromatic nitrile solvent such as benzonitrile and tolunitrile; nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H)-pyrimidinone, 3-methyl-2-oxazolidinone and the like.

(41) Among the exemplified solvents, a carbonate solvent such as a chain carbonate ester solvent, and a cyclic carbonate ester solvent, a lactone solvent and an ether solvent are preferred, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, .gamma.-butyrolactone and .gamma.-valerolactone are more preferred, a carbonate solvent such as dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate is further more preferred. One of the above-described other solvents may be used alone, or two or more other solvents may be used in combination.

(42) Due to its high temperature stability, the silicate composition of the present invention may be advantageously combined with ionic liquid based electrolyte, either in the form of a liquid, gel or solid (e.g. polymer).

(43) The ionic liquids preferably contain exclusively or substantially ions. Examples of cations include those which can be in alkylated form, such as imidazolium, pyridinium, pyrrolidinium, guanidinium, uronium, thiuronium, piperidinium, morpholinium, sulfonium, ammonium, and phosphonium cations. Examples of anions which can be used include halide, tetrafluoroborate, trifluoroacetate, triflate, hexafluorophosphate, phosphinate, and tosylate anions.

(44) Exemplary ionic liquids include the following: N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide, N-butyl-N-trimethylammonium bis(trifluoromethylsulfonyl)imide, triethylsulfonium bis(trifluoromethylsulfonyl)imide, and N, N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide.

(45) Lithium Salt

(46) Suitable electrolytic salts include lithium salts such as, but are not limited to lithium hexafluorophosphate (LiPF.sub.6), lithium perchlorate (LiClO.sub.4), lithium hexafluoroarsenate (LiAsF.sub.6), lithium trifluoromethylsulfonate (LiCF.sub.3SO.sub.3), lithium tetrafluoroborate (LiBF.sub.4), lithium bromide (LiBr), and lithium hexafluoroantimonate (LiSbF.sub.6), lithium bis(trifluoromethanesulfonyl)imide (LiC.sub.2F.sub.6S.sub.2O.sub.6N) and mixtures thereof. The salts can be used in combination with other salts including, without limitation, hydrolyzable salts such as LiPF.sub.6 in any suitable amounts. Typically, the amount of such additional salts ranges from about 0.01 M to about 1.5 M.

(47) Electrodes

(48) Energy storage devices incorporating the silicate composition can employ any suitable cathode and anode. In forming a lithium secondary battery typically the anodes are non-metallic and can be based upon non-graphitizing carbon, natural or artificial graphite carbon, or tin, silicon, or germanium compounds or lithium titanium oxide. In other embodiments, the anode is a lithium metal or lithium metal alloy anode.

(49) In some embodiments, the silicate composition forms part of a polymer composite membrane covering the electrode of the same composition as a polymer based electrolyte. In another embodiment, the silicate forms a glassy film (i.e. between 1 and 60 μm and preferably less than 50 μm and more preferably less than 30 μm) on the outer surface of the electrode. The film may serve as a stable solid electrolyte interphase (SEI) to inhibit dendritic growth of lithium whilst enabling lithium ions to be transported through the film.

(50) The positive electrodes for use in lithium secondary batteries typically are based upon a lithium composite oxide with a transition metal such as cobalt, nickel, manganese, among others and mixtures thereof, or a lithium composite oxide, part of whose lithium sites or transition metal sites are replaced with cobalt, nickel, manganese, aluminium, boron, magnesium, iron, copper, among others and mixtures thereof or iron complex compounds such as ferrocyan blue, berlin green, among others and mixtures thereof. Specific examples of lithium composites for use as positive electrodes include LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2, LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2, LiNi.sub.1-xCo.sub.xO.sub.2 (where x is a number between 0 and 1) and lithium manganese spinel, LiMn.sub.2O.sub.4.

EXAMPLES

(51) Fibres were formed using the sol-gel or melt spinning or blown method. The sol-gel samples are crystalline, whilst unless otherwise specified the melt samples are amorphous.

(52) Melt Spinning Method

(53) Fibres according to the invention have been produced by spinning [made from the melt by forming a molten stream and converting the stream into fibre by permitting the stream to contact one or more spinning wheels], at the applicant's research facilities in Bromborough, England by spinning or alternatively by blowing fibres made from the melt by forming a molten stream and converting the stream into fibre by using an air blast directed at the stream.

(54) Samples

(55) The fibrous samples were pelletised at pressures of 500-700 MPa after having been ground in a pestle and mortar. The green pellets (approximately 15 mm diameter×2 mm depth) were subsequently fired at temperatures ranging from 600-900° C. depending on the specific composition of the fibre. DSC was used to determine the sintering temperature, which was specified as being above the softening point and 25° C. below the crystallisation temperature to ensure the samples were amorphous. The relative density of the resultant pellets was between 67 to 80% of the absolute density of the material. A gold coating was applied with a thickness of about 100 nm to enable a uniform, highly conductive surface that is necessary for the EIS measurements.

(56) Examples 1 to 13 (Table 1) were formed by the melt method as previously described. Comparative example C-1 to C-8 (Table 2) were formed by the sol-gel method as described in co-pending application GB1801684 (page 27, line 21 to page 30, line 18), which is incorporated herein by reference.

(57) Example 11 which has a low ratio of network formers to network modifiers produced a poor quality fibre (from visual inspection the arithmetic fibre diameter was greater than 20 μm and the shot level greater than 60 wt %). As such the compositions were not considered melt formable compositions.

(58) TABLE-US-00001 TABLE 1 Actual Composition (wt %) Conductivity, Sample Target Composition Li.sub.2O ZrO.sub.2 SiO.sub.2 CaO TiO.sub.2 Al.sub.2O.sub.3 La.sub.2O.sub.3 CeO.sub.2 σ.sub.g (Scm.sup.−1) 1 LiAlSiO.sub.4 12.14 0 54.70 0 0 33.15 0 0 3.22 × 10.sup.−5 2 Li.sub.2CaSiO.sub.4 17.71 0 43.46 38.83 0 0 0 0 4.04 × 10.sup.−5 3 LiAlSi.sub.2O.sub.6 6.86 0 69.84 0 0 22.82 0 0 —  4a Li.sub.2ZrSi.sub.6O.sub.15 5.64 22.53 71.83 0 0 0 0 0 1.32 × 10.sup.−4  4b Li.sub.2ZrSi.sub.6O.sub.15 6.75 23.77 69.49 0 0 0 0 0 1.51 × 10.sup.−4 5 Li.sub.2Zr.sub.0.95Ti.sub.0.05Si.sub.6O.sub.15 6.49 21.23 71.35 0 0.93 0 0 0 5.42 × 10.sup.−5 6 Li.sub.2Zr.sub.0.8Ti.sub.0.2Si.sub.6O.sub.15 6.04 18.38 72.57 0 3.01 0 0 0 1.05 × 10.sup.−4 7 Li.sub.2.05Zr.sub.0.95La.sub.0.05Si.sub.6O.sub.15 6.32 20.37 71.98 0 0 0 1.34 0 4.37 × 10.sup.−5 8 Li.sub.2.2Zr.sub.0.8La.sub.0.2Si.sub.6O.sub.15 6.84 17.62 70.20 0 0 0 5.34 0 3.35 × 10.sup.−5 9 Li.sub.3ZrAlSi.sub.5O.sub.15 9.53 22.00 59.00 0 0 9.47 0 0 5.46 × 10.sup.−5 10  Li.sub.2Zr.sub.2Si.sub.5O.sub.15 5.58 40.70 53.71 0 0 0 0 0 6.78 × 10.sup.−5 11  Li.sub.6ZrSi.sub.5O.sub.15 18.96 22.98 58.06 0 0 0 0 0 1.26 × 10.sup.−5 12  Li.sub.2CeSi.sub.6O.sub.15 6.83 0 72.39 0 0 0 0 20.78 2.90 × 10.sup.−5 13  Li.sub.3.3La.sub.0.33Ti.sub.1.7Si.sub.3O.sub.11.5 11.15 0 44.99 0 31.66 0 11.15 0 3.50 × 10.sup.−5

(59) TABLE-US-00002 TABLE 2 Actual Composition (wt %) Conductivity, Sample Target Composition Li.sub.2O ZrO.sub.2 SiO.sub.2 P.sub.2O.sub.5 TiO.sub.2 Al.sub.2O.sub.3 La.sub.2O.sub.3 SrO σ.sub.g (Scm.sup.−1) C-1 Li.sub.0.33La.sub.0.557TiO.sub.3 2.59 0 0 0 46.11 0 51.30 0 7.64 × 10.sup.−5 C-2 Li.sub.7La.sub.3Zr.sub.2O.sub.12 12.70 25.75 0 0 0 0 61.54 0 8.91 × 10.sup.−6 C-3 Li.sub.5.5Al.sub.0.5La.sub.3Zr.sub.2O.sub.12 7.62 23.55 0 0 0 2.60 66.21 0 2.36 × 10.sup.−5 C-4 Li.sub.6.4Al.sub.0.2La.sub.3Zr.sub.2O.sub.12 10.97 24.32 0 0 0 1.17 63.54 0 4.41 × 10.sup.−5 C-5 Li.sub.3.3La.sub.0.3Zr.sub.1.7Si.sub.2PO.sub.12 10.18 36.15 28.18 15.39 0 0 10.09 0 4.23 × 10.sup.−5 C-6 Li.sub.0.4Sr.sub.0.8TiO.sub.3 6.03 0 0 0 81.42 0 0 12.55 5.87 × 10.sup.−5 C-7 Li.sub.4SrAl.sub.2SiO.sub.8 14.54 0 11.84 0 0 45.89 0 27.73 2.55 × 10.sup.−5 C-8 Li.sub.3Al.sub.3SiO.sub.8 17.13 0 58.17 0 0 24.70 0 0 6.93 × 10.sup.−6
Fibre Shrinkage

(60) Tests were performed by making a vacuum formed board in a 75 mm square template (thickness is dependent on amount of sample). The board is measured on all 4 sides using calibrated Vernier calipers at least twice so that an average is used. The board is then heated at a steady rate of 300° C. hr.sup.−1 and held at the desired temperature for 24 hours before cooling. The 4 sides are measured again and the measurements compared to the initial in accordance with ISO 10635.

(61) Sample 1 Results:

(62) TABLE-US-00003 TABLE 3a Temperature ° C. % shrinkage 25 0 1000 0.05 1100 0.3 1200 0.8 1250 2.0 1300 7.9
Sample 4a Results:

(63) TABLE-US-00004 TABLE 3b Temperature ° C. % shrinkage 700 0.8 725 0.8 750 6.6 775 15.9 800 32 900 43.1 1000 43.1
Fibre Diameter

(64) Melt-formed fibre was chopped using an oscillating granulator through a ⅙″ steel mesh. Fibre diameters were determined from SEM images of a sample taken at ×1500 magnification using auto focus. The software macro sweeps across the sample taking 350 images. The images are then analysed using the Scandium™ software package where any fibre with an aspect ratio greater than 3:1 that lies on the central line of the image is measured. All samples below this aspect ratio are not considered fibres.

(65) Sample 2 Results:

(66) Geometric mean diameter: 2.27 μm

(67) Arithmetic mean diameter: 2.47 μm

(68) Standard Deviation: 1.27 μm

(69) Air Classified Material

(70) The collected material was then passed through an air classification process to remove shot from the as-made material. By altering the speed of the rotor it is possible to acquire finer fibres, and reduce the shot content considerably

(71) Sample 4a Results:

(72) Air classified with a blade speed of 1700 rpm and an air speed of 120 m.sup.3 hr.sup.−1.

(73) Geometric mean diameter: 3.83 μm

(74) Arithmetic mean diameter: 5.11 μm

(75) Standard Deviation: 4.18 μm

(76) Reduction of 58 wt % shot to <5 wt %,

(77) Formation of Nanowires.

(78) Sample 4a was subjected to air classification with a blade speed of 10,000 rpm and an air speed of 90 m.sup.3 hr.sup.−1.

(79) Geometric mean diameter: 1.08 μm

(80) Arithmetic mean diameter: 1.28 μm

(81) Standard Deviation: 1.05 μm

(82) FIG. 4 illustrates fibre A (655 nm diameter) and fibre B (490 nm diameter)

(83) Crystalline/Amorphous Form

(84) XRD measurements were taken of: Sample 1, after being fired at 1000° C. (FIG. 1); Sample 2, after being fired at 1000° C. (FIG. 2); Sample 4a, after being fired between 750° C. and 1000° C. (FIG. 3).

(85) The results indicated that:

(86) Sample 1 contained eucryptite (LiAlSiO.sub.4) (peak intensity score: 86).

(87) Sample 2 contained Li.sub.2CaSiO.sub.4, Li.sub.2Ca.sub.2Si.sub.2O.sub.7 and Li.sub.2SiO.sub.3 (peak intensity scores 52, 33 and 25)

(88) Sample 4a remained amorphous up until 820° C. after which the crystalline emerges and predominates at a firing temperature of 1000° C.

(89) Ionic Conductivity

(90) Conductivity measurements were carried out using A.C. impedance spectroscopy [Solartron Modulab manufactured by AMETEK Advanced Measurement Technology: equipment setup of XM CHAS 08; XM PSTAT 1MS/s; XM PSTAT AUX and XM BOOSTER 2A] over a range of 1 MHz to 10 mHz at room temperature. The grain conductivity was calculated from the high frequency resistance.

(91) The results (Table 1) highlight that compositions under the present invention produce ionic conductivity with good utility for use in energy storage devices. In particular, silicate compositions further comprising zirconium exhibit excellent ionic conductivity compared to the comparative examples (Table 2).

(92) TABLE-US-00005 TABLE 4 Sample (x + y)/(v + w) v/(v + w + x + y) 4 2.0 0.22 5 2.0 0.22 6 2.0 0.22 7 1.97 0.22 8 1.88 0.24 9 1.5 0.3 10 1.25 0.22 11 0.71 0.5 12 2.0 0.22 13 0.56 0.39

(93) As indicated in Table 4, Sample 11 had relatively high lithium content (v/(v+w+x+y) and a relatively low ratio of network formers (x+y) to network modifiers (v+w). In addition to this sample being more difficult to fiberize, the higher lithium content correlated with a lower ionic conductivity.

(94) Formation of Composite Electrolyte Membrane (Electrolyte Matrix)

(95) Polyacrylonitrile 2.17 wt % (PAN) and 1.29 wt % LiClO.sub.4 salt were combined in dimethylformamide (DMF), the solution was stirred at 80° C. for 5 hrs. A sufficient amount of sample 4a (arithmetic fibre diameter: 5.11 μm) fibre was added to form a slurry, that would result in a 5.0 wt % fibre content (59.6 wt % PAN and 35.4 wt % LiClO.sub.4) of the final dried composite material, and was stirred vigorously for 5 hrs in a sealed vial. The mixture was cast onto a glass substrate and dried in a vacuum oven overnight at 50° C. to form the composite membrane material of about 50-60 μm thickness. It is expected that a lower film thickness may be achieved with a further dilution with DMF in the starting solution. A membrane was cut into a 19 mm diameter disc and placed between stainless steel plates and ionic conductivity (total) measurements (σ.sub.total) were carried out using A.C. impedance spectroscopy over a frequency range of 1 MHz-10 mHz and a temperature range from 22° C. to 80° C.

(96) TABLE-US-00006 TABLE 5 Temperature Conductivity σ.sub.t (Scm.sup.−1) 22° C. (room temperature) 1.95 × 10.sup.−4 40° C. 3.85 × 10.sup.−4 60° C. 6.35 × 10.sup.−4 80° C. 1.06 × 10.sup.−3

(97) The results (Table 5) show an improvement in conductivity compared to electrolyte matrixes comprising 5 wt % nanowires of Li.sub.7La.sub.3Zr.sub.2O.sub.12 (LLZO) reported in Yang et al., ACS Appl. Mater. Interfaces, 2017, 9, 21773 and 3 wt % nanowires of Li.sub.0.33La.sub.0.557TiO.sub.3 (LLTO) reported in Liu et al., Nature Energy, 2017, 2, 17035: using comparable methodology and based materials (PAN and LiClO.sub.4) and a significant increase in comparison to the membrane without the addition of inorganic fibres.

(98) This invention has been described herein in considerable detail to provide those skilled in the art with information relevant to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by different equipment, materials and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.