Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
  • H01B1/12—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances organic substances
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
  • H01B1/12—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances organic substances
  • H01B1/122—Ionic conductors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/403—Cells and electrode assemblies
  • G01N27/406—Cells and probes with solid electrolytes
  • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
  • G01N27/4073—Composition or fabrication of the solid electrolyte
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/15—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
  • G02F1/1514—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material
  • G02F1/1523—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material comprising inorganic material
  • G02F1/1525—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material comprising inorganic material characterised by a particular ion transporting layer, e.g. electrolyte
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention provides a composition for use as a polymer electrolyte, a process for preparing said composition, and its use, particularly in coulometers, displays, smart window, cells and batteries.
• Liquid electrolytes tend to suffer from problems relating to the loss of electrolyte from the cell case and require the use of cell seals. Under extreme conditions, for example during short circuit abuse of cells, the local heating within the cell case can lead to seal rupture, even with the most sophisticated seal and cell case design.
• solid electrolytes offer many advantages over liquid electrolytes such as more efficient use of space (no separator required) , no risk of electrolyte spillage, simplification of seal design with resulting reduction of cost, extended temperature range of cell operation, better cathode operation and improved abuse resistance.
• Typical disadvantages of some solid electrolytes are that they tend to have a relatively low ionic conductivity and a poor mechanical compatibility with certain types of electrode materials.
• Such electrolytes may be used in coulometers, smart windows or displays, cells and batteries.
• Advantages of polymer electrolytes typically include low processing costs, excellent mechanical properties, the possibility of using a large area/thin film format, variable cell configuration, low device weight, good chemical stability, good thermal stability and access to lithium chemistry.
• Poly (ethylene oxide) (PEO) was the first polymer in which salt solubilisation and ionic transport were recognised.
• Yamamoto et al describe the preparation and properties of polymer solid electrolytes based on poly (vinyl alcohol) (PVA) and poly [arylene (1, 3- imidazolidene-2, 4, 5-trione-l, 3-diyl) ] (poly (parabamic acid) , PPA) .
• the present invention provides a composition for use as a polymer electrolyte, which composition comprises one or more polar materials and one or more polyesters of formula III,
• x is from 1 to 5 and each unit B may be identical or different and is of the structure V,
• R and R are each, independently, hydrogen, an optionally substituted hydrocarbyl group or an inert functional group.
• polar materials in the present invention is meant salts and proton conductor systems. Typical proton conductor systems include phosphoric acid and sulphamide.
• hydrocarbyl group in the present invention is meant a group containing only carbon and hydrogen. Unless otherwise stated, the number of carbon atoms is preferably from 1 to 4. Examples of hydrocarbyl groups include methyl, ethyl and propyl.
• the phrase "optionally substituted hydrocarbyl” is used to describe hydrocarbyl groups optionally containing one or more "inert” heteroatom-containing functional groups.
• inert is meant that the functional groups do not interfere to any substantial degree with the ionic conductivity and/or mechanical properties of the resulting composition.
• Said inert groups may include ethers and polyethers . Such inert groups may act as plasticisers. Non-limiting examples of such inert groups are -CH2CH2OCH3 and -CH2CH2OCH2CH2OCH3.
• compositions according to the present invention generally comprise polyesters having a weight average molecular weight, M ⁇ , greater than 30,000, preferably greater than 75,000, and more preferably greater than 250,000.
• M ⁇ weight average molecular weight
• the weight average molecular weight, M ⁇ , of the polyester may be determined by several techniques which give closely similar results. M ⁇ may be easily determined by gel permeation chromatography (GPC) with calibration of the polyester as will be appreciated by those skilled in the art.
• ⁇ may be determined “ by light scattering, " as “ described in “ ASTM D 4001-93.
• Said polyesters generally have a glass transition temperature, Tg, in the range of from -60 to 20 °C, preferably in the range of from -50 to 10 °C, and more preferably in the range of from -30 to 5 °C.
• Polyesters according to the present invention are generally polymers of carbonic acid made by the condensation polymerisation of one or more different polyhydridic alcohols with phosgene or derivatives thereof. Said polyesters may also be formed by the ring opening polymerisation of a cyclic carbonate as described previously in the art or by transesterification with dialkylcarbonate or alkylene carbonate.
• Polyhydric alcohols that may be used in the preparation of said polyesters include 1, 2-ethanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1,6- hexanediol, 2-methyl-l, 3-propanediol, 2, 2-dimethyl-l, 3- propanediol, trimethylolethane, glycerine and pentaerythritol .
• polyesters in respect of the present invention are poly (trimethylene carbonate) and esters of other polyhydric alcohols described above.
• the amount of polyester incorporated in the composition is generally in the range of from 50 to 99 wt . %, preferably in the range of from 60 to 94 wt. %, and more preferably in the range of from 65 to 83 wt. % based on the composition.
• the amount of polar material incorporated in the composition is generally in the range of from 50 to 1 wt. %, preferably in the range of from 40 to 6 wt. %, and more preferably in the range of from 35 to 17 wt. % based on the composition.
• composition of the present invention may comprise " salts such as quaternary ammonium salts,- fo -example- ammonium thiocyanate and/or metal salts.
• Metal salts that may be generally employed in the composition of the present invention include those wherein the metal is selected from lithium, sodium, potassium, nickel, zinc, silver and lanthanides such as neodymiun, europium, erbium and thulium.
• preferred metal salts are lithium metal salts.
• Particularly preferred lithium metal salts are lithium triflate, lithium perchlorate, lithium bromide, lithium chloride, lithium iodide, lithium bis (trifluoromethylsulphonyl) imide, lithium tetrafluoroborate, lithium trifluoromethanesulphonate, lithium hexafluoroarsenate (V) , lithium thiocyanate, lithium acetate, lithium dichlorosulphonimide, lithium fluorochlorosulphonimide, lithium sulphonate and lithium tetrachloroaluminate .
• compositions may be prepared with a range of salt concentrations by adding different quantities of the salt to the composition.
• the composition of the resulting mixture may be identified by indicating the value of n.
• n is the molar ratio of monomer units per mole of added salt.
• n is in the range of from 1 to 100, preferably in the range of from 1 to 80, more preferably in the range of from 1 to 15 and most preferably in the range of from 1 to 5.
• the composition is a solid, that is to say, the polymer electrolyte is a solid, solvent-free polymer electrolyte.
• the composition may further comprise a solvent.
• the polyester may act as an immobiliser to a non-aqueous electrolyte of a salt in a solvent, for example, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetrachloroaluminate and /or lithium bromide in acetonitrile, propylene carbonate, dimethylsulphoxide (DMSO) , etc.
• composition according to the present invention may further comprise one or more plasticiser compounds.
• Said plasticiser compounds may be typically selected from propylene carbonate, ethylene carbonate, dimethylsulphoxide, dioctyl phthlate, dibutyl phthalate, diethyl phthalate, dimethyl phthalate, butyrolactone, dimethyl carbonate, diethyl carbonate, bis (2-ethylhexyl) sebacate and/or trimethylene carbonate.
• Plasticisers may be typically used at doping levels in the range of from 1 to 50 wt . %, preferably in the range of from 1 to 20 wt. % and more preferably in the range of from 5 to 15 wt . %.
• compositions according to the present invention may be prepared by weighing out polyester and salt components and adding a volume of solvent to produce a solution comprising a homogeneous mixture of the components .
• Said solution may be quite viscous in character.
• the solvent of said solution may be allowed to evaporate under an inert atmosphere. Such a procedure typically allows the formation of a thin flexible film of the composition.
• Solvents that may be typically used in the formation of compositions according to the present include dry tetrahydrofuran/ dry- acetonitrile,- -dry methanol an -dry ethanol.
• the inert atmosphere that is typically employed in the formation of compositions according to the present invention may include dry argon, dry nitrogen, or dry helium.
• the composition may be prepared by polymerising polyester monomers in situ in the presence of the salt.
• compositions according to the present invention may be used as polymer electrolytes in coulometers, displays, smart windows, cells and batteries.
• the present invention therefore also provides a cell and/or battery comprising said composition.
• smart window is meant a variable transmission device wherein the transmission of light through the device may be controlled electrochemically, darkening a thin anode or cathode on the inner surface of the glass layer of the window.
• Figure 1 shows the variation of conductivity with reciprocal temperature for polymer electrolytes based on a (TMC)n lithium triflate system
• Figure 2 shows the variation of conductivity with reciprocal temperature for polymer electrolytes based on a (TMC)n lithium perchlorate system
• FIG. 3 shows conductivity isotherms for polymer electrolytes based on a (TMC)n lithium triflate system
• Figure 4 shows conductivity isotherms for polymer electrolytes based on a (TMC)n lithium perchlorate system
• FIG. 5 shows- the- effect of -bis-(2-ethylhexyl)- sebacate upon the conductivity of a (TMC) 9 lithium triflate system
• Figure 6 shows the effect of diethyl phthalate upon the conductivity of a (TMC) g lithium triflate system
• FIG. 7 shows the effect of trimethylene carbonate upon the conductivity of a (TMC) 9 lithium triflate system
• FIG 8 shows thermogravimetric analysis of pure p(TMC) and polymer electrolytes based on a (TMC)n lithium perchlorate system and a (TMC)n lithium triflate system;
• Figure 9 shows a comparison of temperatures of onset of weight loss of electrolytes based on lithium perchlorate and lithium triflate;
• Figure 10 shows thermal analysis of polymer electrolytes based on a (TMC)n lithium triflate system
• Figure 11 shows thermal analysis of polymer electrolytes based on a (TMC)n lithium perchlorate system.
• Lithium triflate (95 %, ex. Aldrich) and lithium perchlorate (99.99 %, ex. Aldrich) were dried under vacuum at 180 and 150 °C respectively, for 7 days and then stored in a high integrity, dry argon-filled glovebox.
• the resulting solutions were cast into glass rings on glass plates and the solvent was then removed slowly by locating the moulds in an isolated chamber within the preparative glovebox.
• the atmosphere of the chamber was re-circulated through a column of molecular sieves to effect a slow evaporation and to form films of about 150 ⁇ m thickness. These films were dried at 65 °C under vacuum for 3 days to remove residual solvent.
• the sample was measured with a type K thermocouple placed close to the electrolyte film and impedance measurements were carried out with a Solartron 1250 Frequency Response Analyser and 1286 Electrochemical Interface, between 25 and 100 °C. Measurements of conductivity were effected during heating cycles and at temperature intervals of about 7 °C. The reproducibility of conductivities obtained in initial and subsequent heating cycles was extremely good and taken as confirmation of the efficiency of the support operation and " mechanical " " stability of " the " samples .
• Polymer electrolyte film sections were subjected to thermal analysis under a flowing argon atmosphere between -40 and 350 °C and at a heating rate of 5 deg.min using a Mettler TCll controller and a DSC 20 oven. Samples in the form of disks were cut from polymer films and presented for analysis in 40 ⁇ l aluminium cans with perforated lids.
• Samples for thermogravimetric studies were also prepared by cutting sections of suitable dimensions from electrolyte films. These sections were transferred to open platinum crucibles and analysed using a Rheometric Scientific thermobalance operating under an argon atmosphere. A heating rate of 5 deg.min was used to analyse all the electrolyte samples.
• the total ionic conductivity of lithium perchlorate-based p (TMC) electrolytes continues to increase with salt concentrations to very high compositions of added salt.
• the p(TMC) polymer as an amorphous, polar macromolecular host, is a more suitable solvent for the preparation of polymer electrolytes than PEO. Even without additives, the electrolytes display encouraging levels of performance which may be further improved with the use of suitable free-volume enhancing components.
• a series of electrolytes based on a constant lithium triflate concentration was prepared with the inclusion of a plasticiser molecule in the casting solution.
• Plasticisers bis (2-ethylhexyl) sebacate, diethyl phthalate and trimethylene carbonate were used at doping levels of between 5 and 15 wt. %. As expected, the presence of plasticiser increased the ionic conductivity ( Figures 5 to 7) . However, at doping levels of greater than about 15 wt . %, the mechanical properties began to degrade and the material became gel-like.
• thermogravimetric studies are consistent with this interpretation and the thermograms of pure polymer, and electrolytes containing high concentrations of lithium perchlorate or lithium triflate are illustrated in Figure 8.
• the onset of the degradation process is dependent upon electrolyte composition, confirming that the salt has a destabilising influence upon polymer host.
• the pure host polymer p(TMC) began to degrade thermally at a temperature close to 230 °C.
• Polymer electrolytes with values of n between 85 and 2 were found to be less thermally stable than the pure polymer. Electrolytes with high concentrations of lithium perchlorate were found to degrade at about 160 °C while lithium triflate-based materials were stable to approximately 180 °C. These thermal stabilities are considered to be adequate for applications of the electrolytes in cells or batteries operating at low or moderate temperatures .
• Lithium perchlorate-containing electrolytes show thermal behaviour which is similar to that observed with lithium triflate-based films at low temperatures, but with a completely different degradation thermogram. As may be confirmed by reference to Figures 10 and 11, while the onset of the perchlorate degradation is similar to the process observed with the triflate, once initiated, the electrolyte samples suffer a strongly exothermic process, the intensity of which is dependent on the amount of salt present in the sample.
• the polymer electrolyte, being mechanically flexible will adapt to such changes in electrode dimension, maintaining ionic contact with the electrode material.

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