Classifications

• • 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
• • 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
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0085—Immobilising or gelification of electrolyte
• • 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

• Figure 2A is a schematic illustration of a plurality of linear polymer dib locks that make up a two- phase nanostructured gel polymer electrolyte.
• a nanostructured gel polymer electrolyte is used in an electrochemical cell in a separator region between a positive electrode and a negative electrode.
• the negative electrode is lithium metal or some alloy thereof which is highly reactive with fluorinated species.
• the nanostructured gel polymer electrolyte contains a liquid electrolyte [solvent(s) and salt(s)] that promotes conduction of ions through the nanostructured gel polymer electrolyte separator.
• the first domain 210-x is a conductive domain; polymer blocks 212-x contain a polymer that is ionically conductive by itself and/or that provides a matrix into which an ionically-conductive liquid electrolyte can be absorbed.
• the second domain 220-x is a structural domain; polymer blocks 222-x contain a polymer that has high mechanical strength.
• the first domain 210-x is a structural domain; polymer blocks 212-x contain a polymer that has high mechanical strength.
• the second domain 220-x is a conductive domain; polymer blocks 222-x contain a polymer that is ionically conductive by itself and/or that provides a matrix into which an ionically- conductive liquid electrolyte can be absorbed.
• Dib locks can arrange themselves into a variety of morphologies, as is well known in the art.
• the diblocks may arrange themselves into any geometrically possible morphology without limitation. Examples of possible morphologies include, but are not limited to lamellar, branched, cylindrical, and gyroid.
• the first domains 315-x contain a conductive phase and the second domains 325-x contain a structural phase. Such an arrangement can result in a nanostructured gel polymer electrolyte with higher conductivity than for morphologies with no perforations/extensions.
• the first domains 315-x contain a structural phase and the second domains 325-x contain a conductive phase. Such an arrangement can result in a nanostructured gel polymer electrolyte with greater mechanical strength than for morphologies with no perforations/extensions.
• FIG. 5 is a schematic illustration of a portion of a two-phase nanostructured gel polymer electrolyte with alternating regions of a first domain 510-x and a second domain 520-x, according to an embodiment of the invention.
• the two-phase structure is made up from a plurality of triblock copolymers, such as those shown in Figure 4.
• the first domains 510-1, 510-2 contain polymer blocks 512 of a first phase.
• the second domain 520-1 contains polymer blocks 522-1, 522-2 of a second phase.
• the polymer blocks 522- 1 522-2 are not covalently bonded to one another, but can slide relative to each other in the region where their ends meet.
• the first domains 510-x are conductive domains; the polymer blocks 512 contain a polymer that is ionically conductive by itself and/or that provides a matrix into which an ionically-conductive liquid electrolyte can be absorbed.
• the second domains 520-x are structural domains; the polymer blocks 522-x contain a polymer that has high mechanical strength.
• the first domains 510-x are structural domains; the polymer blocks 512 contain a polymer that that has high mechanical strength.
• the second domains 520-x are conductive domains; the polymer blocks 522-x contain a polymer is ionically conductive by itself and/or that provides a matrix into which an ionically-conductive liquid electrolyte can be absorbed.
• a two-phase nanostructured gel polymer electrolyte made from triblock copolymers may be easier to handle during processing than one made from diblock copolymers.
• diblock structures each block copolymer chain is part of two domains.
• triblock structures each block copolymer chain is part of three domains.
• the number of possible physical entanglements per chain increases with the number of domains of which the chain is a part.
• the toughness of the overall structure increases with the number of physical entanglements. Increases toughness can be very important in making the block copolymer material easy to process.
• the polymer block 622 of the second type contains a polymer that has high mechanical strength.
• the polymer block 632 of the third type contains a polymer that enhances or adds a desirable property to an electrolyte made from the plurality 610 of the linear polymer triblocks.
• the roles of the polymer blocks 612, 622, 632 can be changed as long as one of the blocks is ionically conductive, one of the blocks has high mechanical strength, and one of the blocks enhances or adds a desirable property to an electrolyte made from the plurality 610 of the linear polymer triblocks.
• the second domains 720-x are conductive domains; the polymer blocks 722 contain a polymer that is ionically conductive by itself and/or that provides a matrix into which an ionically-conductive liquid electrolyte can be absorbed.
• the first domains 710-x are structural domains; the polymer blocks 712-x contain a polymer that has high mechanical strength.
• the third domains 730-x add other desirable properties; the polymer blocks 732-x contain a polymer that enhances or adds a desirable property to an electrolyte.
• the third domains 730-x can be chosen to increase the overall toughness of the nanostructured gel polymer electrolyte, making it easier to process.
• the roles of the first domains 710-x and the third domains 730- x are reversed.
• the structural polymer has a modulus in excess of 1 x 10 6 Pa at electrochemical cell operating temperatures of interest. In other arrangements, it is useful if the structural polymer has a modulus in excess of IxIO 7 Pa at electrochemical cell operating temperatures of interest. It is especially useful if, in its homopolymer state, the structural polymer swells less than 5% in the presence of the liquid electrolyte that is used in the conductive polymer.
• the third phase polymer may be rubbery or have a glass transition temperature lower than the electrochemical cell operating and processing temperatures of interest. It is useful if all materials in the nanostructured gel polymer electrolyte are mutually immiscible.
• Examples of polymers that can be used in the conductive phase of the nanostructured gel polymer electrolyte include, but are not limited to, polyethers, linear copolymers, and polyamines.
• polyethers polyethylene oxide is used.
• a linear copolymer containing an ether is used.
• linear polyethers, linear polyacronitriles, linear polyvinylalcohols, and linear polyacrylates can be used.
• a liquid electrolyte that is added to the conductive phase contains a solvent and a salt.
• solvents include, but are not limited to polar additives such as substituted ethers, substituted amines, substituted amides, substituted phosphazenes, substituted PEGs (see paragraph above), alkyl carbonates, nitriles, boranes, and lactones.
• the solvent has a molecular weight of no more than 5,000 Daltons. In another arrangement, the solvent has a molecular weight of no more than 1000 Daltons.
• An exemplary liquid electrolyte may be characterized by an ionic conductivity of at least 1x10 4 Scm "1 at 25°C.
• an exemplary liquid electrolyte may be characterized by an ionic conductivity of at least 1x10 3 Scm 4 at 25°C. It is especially useful if, in its homopolymer state, the polymer used for the structural phase swells less than 5% in the presence of the solvent that is used in the liquid electrolyte.
• Suitable examples include alkali metal salts, quaternary ammonium salts such as (CHs) 4 NBF 6 , quaternary phosphonium salts such as (CHs) 4 PBF 6 , transition metal salts such as AgClO 4 , or protonic acids such as hydrochloric acid, perchloric acid, and fluoroboric acid, and of these, alkali metal salts, quaternary ammonium salts, quaternary phosphonium salts, and transition metal salts are preferred.
• suitable electrolyte salts include conventional alkali metal salts such as metal salts selected from the group consisting of chlorides, bromides, sulfates, nitrates, sulfides, hydrides, nitrides, phosphides, sulfonamides, triflates, thiocynates, perchlorates, borates, or selenides of lithium, sodium, potassium, silver, barium, lead, calcium, ruthenium, tantalum, rhodium, iridium, cobalt, nickel, molybdenum, tungsten or vanadium.
• the electrolyte salts may be used either singularly, or in mixtures of two or more different salts.
• electrolytes are made by combining the polymers with various kinds of salts. Examples include, but are not limited to AgSO 3 CF 3 , NaSCN, NaSO 3 CF 3 , KTFSI, NaTFSI, Ba(TFSI) 2 , Pb(TFSI) 2 , and Ca(TFSI) 2 .
• the conductive phase also contains a plurality of ceramic particles, such as Al 2 O 3 particles, TiO 2 particles, and/or SiO 2 particles.
• the ceramic particles have a smallest dimension of no more than 5 nanometers.
• Examples of polymers for use in the structural phase of the nanostructured gel polymer electrolyte include, but are not limited to, polystyrene, polymethacrylate, polyvinylpyridine, polyvinylcyclohexane, polyimide, polyamide, and polypropylene.
• Other materials that can be used for the structural phase include, but are not limited to copolymers that contain styrene, methacrylate, and vinylpyridine.
• the structural phase is made of polymer blocks that have a bulk modulus greater than 10 6 Pa at 90 0 C. It is especially useful if, in its homopolymer state, the polymer used for the structural phase swells less than 5% in the presence of the solvent that is used in the liquid electrolyte.
• Examples of polymers for use in the third phase of the nanostructured gel polymer electrolyte include, but are not limited to rubbery polymers made of polysiloxanes, polyacrylates, or polydienes.
• An exemplary polysiloxane is polydimethylsiloxane.
• An exemplary polyacrylate is poly(2-ethylhexyl acrylate), polydecyl methacrylate or polylauryl methacrylate.
• An exemplary polydiene is polyisoprene or polybutadiene.
• the third phase is made of one of several types of linear polymer blocks. The third phase may be a minor phase and may increase the overall toughness of the nanostructured gel polymer electrolyte.
• the nanostructured gel diblock copolymer electrolyte can be made of any of several materials.
• the nanostructured gel polymer electrolyte is made of poly(styrene-block-ethylene oxide) (SEO) diblock copolymers containing a first conductive phase of polyethylene oxide and a second structural phase of polystyrene.
• SEO poly(styrene-block-ethylene oxide)
• a SEO diblock copolymer electrolyte can have a molecular weight between about 100,000 and 1,000,000 Daltons.
• a SEO diblock copolymer electrolyte has a molecular weight between about 100,000 and 500,000 Daltons.
• a SEO diblock copolymer electrolyte has molecular weight of about 400,000 Daltons.
• the SEO diblock copolymer electrolyte is brittle, and can break apart easily when attempts are made to form a free-standing thin film.
• the toughness of the nanostructured gel polymer electrolyte increases with molecular weight.
• the two-phase nanostructured gel triblock copolymer electrolyte can be made of any of several materials.
• the nanostructured gel polymer electrolyte is made of poly(styrene-block-ethylene oxide -block-styrene) (SEOS) triblock copolymers containing a first structural phase and a second conductive phase.
• SEOS poly(styrene-block-ethylene oxide -block-styrene) triblock copolymers containing a first structural phase and a second conductive phase.
• SEOS poly(styrene-block-ethylene oxide -block-styrene)
• SEOS poly(styrene-block-ethylene oxide -block-styrene) triblock copolymers containing a first structural phase and a second conductive phase.
• SEOS poly(styrene-block-ethylene oxide -block-styrene)
• SEOS poly(styrene-block-ethylene oxide -
• a SEO triblock copolymer electrolyte has molecular weight of about 400,000 Daltons. In some arrangements, the SEOS triblock copolymer electrolyte is not brittle, and does not break apart easily when attempts are made to form a free-standing thin film.
• Figure 9 is a plot of ionic conductivity as a function of inverse temperature for two nanostructured gel polymer electrolytes, according to embodiments of the invention.
• Both Copolymer 1 and Copolymer 2 are two-phase nanostructured gel polymer electrolytes with 60 weight% conductive domain and 40 wt% structural domain.
• Copolymer 1 contains 79 wt% polyethylene oxide (PEO) and 21 wt% ethylene carbonate (EC), a liquid electrolyte.
• Copolymer 2 contains 28 wt% PEO and 72 wt% EC.
• the graph shows a higher ionic conductivity for Copolymer 2, which has more ethylene carbide than Copolymer 1 , indicating that the highly-gelled conductive phase has increased conductivity as compared to the "drier" conductive phase.
• an exemplary method for synthesizing poly(styreneblock- ethylene oxide) (SEO) diblock copolymer includes synthesizing polystyrene (PS) as a first block and synthesizing ethylene oxide (EO) as a second block.
• the method includes distilling purified benzene into a reactor on a vacuum line and taking the reactor from the vacuum line into a glove box where an initiator such as s-butyllithium may be added.
• the method includes returning the reactor to the vacuum line to be degassed and distilling styrene monomers into the reactor.
• the method includes heating the reactor to room temperature, stirring for at least six hours, and isolating an aliquot of living polystyrene precursors in the glove box for molecular weight determination.
• the method includes returning the reactor to the vacuum line to be thoroughly degassed and distilling a few milliliters of ethylene oxide into the degassed reactor.
• the method includes heating the reactor to a room temperature, stirring for two hours, taking the reactor back to the glove box, and adding a strong base in 1 : 1 molar ratio to an initiator.
• the method includes adding t-butyl phosphazene base (t-BuP4) as the strong base.
• the method includes, after the addition of the bifunctional terminator, allowing the reaction mixture to stir for 5 days to enable the slow reaction to proceed to completion.
• the method includes adding methanol to terminate any remaining living chains and isolating SEOS triblock copolymers by precipitation in hexane and vacuum freeze drying from benzene.
• the method includes returning the reactor to the vacuum line to be thoroughly degassed, stirring at room temperature for 12 hours to allow the t-BuP4 to react with the ethylene oxide -terminated PS chains, and distilling a desired amount of ethylene oxide into the reactor using dry ice/isopropanol.
• the method includes heating the reactor to 50 0 C, stirring for five days in a hot water bath, and returning the reactor to the glove box.
• the method includes terminating the living EOSEO triblock copolymer using methanol and isolating the EOSEO triblock copolymer by precipitation in hexane and by vacuum freeze drying from benzene.
• the method includes returning the reactor to the vacuum line to be thoroughly degassed, stirring at room temperature for 12 hours to allow the t-BuP4 to react with the ethylene oxide-terminated PI-PS chains, and distilling a desired amount of ethylene oxide into the reactor using dry ice/isopropanol.
• the method includes heating the reactor to 50 0 C and stirring for five days in a hot water bath.
• the method includes returning the reactor to the glove box, terminating the living ISEO triblock copolymers using methanol, and isolating the ISEO diblock copolymer by precipitation in hexane and vacuum freeze drying from benzene.
• starting material benzene may be purchased from Aldrich.
• An exemplary method for purifying benzene includes stirring on freshly ground calcium hydride for at least eight hours in a long neck flask attached to a vacuum line. The method includes freezing the mixture of calcium hydride using liquid nitrogen and degassing the mixture under vacuum. The method includes distilling benzene out of the calcium hydride mixture onto a sbutyllithium purification stage, stirring the benzene on the s-butyllithium for at least eight hours, and degassing.
• starting material styrene may be purchased from Aldrich.
• An exemplary purified styrene may be stored in a freezer prior to use.
• the method includes pouring styrene into a flask attached to the vacuum line, freezing and degassing.
• the method includes pipetting dibutylmagnesium (1.0 M in heptane) into a second flask in a glove box, adding ten mL of dibutylmagnesium for every 100 mL of styrene to purify.
• the method includes attaching the flask to the vacuum line, distilling the heptane out of the dibutylmagnesium flask, distilling the styrene onto the dibutylmagnesium, stirring the styrene on the dibutylmagnesium for at least eight hours, and thoroughly degassing.
• starting material isoprene may be purchased from Aldrich.
• An exemplary purified isoprene may be stored in a freezer prior to use.
• the method includes pouring isoprene into a long neck flask containing freshly ground calcium hydride, attaching the flaks to a vacuum line, and freezing and degassing.
• the method includes pipetting s-butyllithium (1.4 M in cyclohexane) into a second long neck flask, adding ten mL of s-butyllithium for every 100 mL of isoprene to purify, distilling the cyclohexane of the sbutyllithium flask, and distilling the isoprene into the dried s-butyllithium using dry ice/isopropanol as the coolant.
• the method includes removing the mixture from the dry ice and stirring without coolant for three minutes, ensuring that the flask is not left out of the cooling bath for longer than three minutes.
• the method includes freezing the mixture in liquid nitrogen, degassing, repeating the stirring/degassing procedure twice more to enhance purity, and distilling isoprene into a measuring ampoule to get the isoprene to be ready to use.
• starting material ethylene oxide may be purchased from Aldrich.
• An exemplary method includes condensing ethylene oxide into a long neck flask containing freshly ground calcium hydride using dry ice/isopropanol as the coolant and freezing and degassing ethylene oxide, which may be stored in a gas cylinder in a refrigerator prior to use.
• the method includes stirring ethylene oxide for a minimum of eight hours on the calcium hydride while packed in dry ice/isopropanol, pipetting n-butyllithium into a second long neck flask, attaching the flask to the vacuum line and degassing.
• the method includes distilling ethylene oxide out of the nbutyllithium into a measuring ampoule using dry ice/isopropanol as the coolant and keeping the ampoule at 0 0 C to get the ethylene oxide to be ready to use.
• starting material dichlorodimethylsilane may be purchased from Aldrich.
• the method includes stirring on freshly ground calcium hydride for at least eight hours in a long neck flask attached to a vacuum line. The method includes freezing the dichlorodimethylsilane and degassing thoroughly prior to use.
• the specific steps include preparing salt components of an exemplary electrolyte.
• the method for preparing salt components includes drying Lithium bis(trifluoromethane)sulfonimide (Li TFSI) purchased from Aldrich prior to use.
• the method includes, due to the high hygroscopic nature of Li TFSI, handling the Li TFSI only in the argon glovebox.
• the method includes heating Li TFSI in the glovebox antechamber at 150 0 C under vacuum for 12 hours.
• the method includes keeping Li TFSI in the argon filled glovebox until the gels were prepared.
• the method includes freezing the TFSI/EC solutions using dry ice and freeze drying the frozen solutions under vacuum.
• the method includes applying vacuum for 2 days to ensure removal of the benzene and acetonitrile from the mixture.
• the method includes returning the dried samples to the glovebox making sure not to expose them to air.
• the method includes compression molding the samples and using the sample to make battery electrolytes.
• the specific steps include selecting certain polymers as additives.
• addition of the EC as a solvent to the polymersalt electrolytes resulted in increased conductivity as compared to the "neat" polymer-salt electrolyte.
• the polymers swell too much in the EC solvent. This results in a loss of mechanical properties of the electrolyte.
• EC swells the conductive phase of the copolymers and does not swell the mechanically rigid phase, it is possible to add a small enough amount of EC to the copolymers to increase conductivity while maintaining mechanical integrity.
• the method includes adding a small amount of EC as additives to the gel electrolyte system such that the mechanically rigid phase occupies a sufficient volume fraction of the gel to maintain and further promote structural integrity.
• the above disclosure provides for an electrolyte material exhibiting both high mechanical stability and high conductivity, that provide controlled nanostructured pathways for ionic flow and that is adaptable to be manufactured using conventional polymer processing methods. While the current inventions have been described in the context of the above specific embodiments, modifications and variations are possible. For example, the concept of using a multi-phase polymer system can be extended to other gel electrolyte systems, both aqueous and non-aqueous, to improve the mechanical strength and conductivity of battery electrolytes. Accordingly, the scope and breadth of the present invention should not be limited by the specific embodiments described above and should instead be determined by the following claims and their full extend of equivalents.

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