Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
  • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
  • H01M4/602—Polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • 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

• This invention is directed to novel encapsulated sub-micron sulfur particles which are suitable for utility as an electrode active material.
• the invention is directed to sub-micron sulfur particles which are formed in the presence of a mixed hydrophilic hydrophobic copolymer.
• the resulting encapsulated sulfur sub-micron core particle is coated with a membrane of layers of self-assembling conductive polymer layers, each successive layer having a charge opposite to the previous layer.
• the invention is also directed to a cathode containing the membrane coated encapsulated sulfur sub-micron particles and an electrochemical cell or battery containing the cathode.
• the invention is further directed to a lithium-sulfur battery containing the membrane coated carbon-sulfur composite cathode.
• MIEC mixed ionic-electronic conductor
• the oxidized (p-doped) form of PPy is treated with an acid for removing an electron from its backbone and produces a free radical and cation (also called a polaron).
• the cation couples with the sulfonic acid moiety in PAAMPSA, resulting in a
• the S-MIEC composite cathode showed improved electrochemical stability. It is claimed that the polyelectrolyte complex facilitates ion and electron transfer while capturing intermediate polysulfides via ion exchange. A capacity of 500 mAh/g S (45% sulfur in cathode) can be retained after 50 cycles at a high rate of 1C.
• a concept similar to that used by Fu et al is the utilization of an ionic shield for polysulfides.
• Sulfonate-end capped (S0 3 ⁇ ) perfluoroalkyl ether groups of Nafion coated Celgard 2400 allow ion hopping of positively charged Li + but inhibits hopping of negative polysulfides due to coulombic interactions (Huang, J.-Q.; Zhang, Q.; Peng, H.-J.; Liu, X.-Y.; Qian, W.-Z.; Wei, F. Ionic Shield for Polysulfides towards Highly-Stable Lithium-sulfur Batteries. Energy Environ. Sci. 2013, 7, 347-353).
• This cation "permselective membrane” is claimed to act as an electrostatic shield for polysulfide ions and retained about 425 mAh/g capacity after 500 cycles at a high rate of 1C (50%) sulfur cathode content).
• Two oxidation waves were reported in the cyclic voltammograms corresponding to a stepwise transformation between S 8 and Li 2 S 4 .
• PEML Poly(diallyalmmonium chloride) (PDAD) and poly(styrene sulfonate) (PSS) were employed to form the PEML's.
• PDAD diallyalmmonium chloride
• PSS poly(styrene sulfonate)
• Such PEMLs have been reported to benefit from highly conformal coverage and precise control over their assembly. They have also been reported to be flexible and self-healing. These properties are ideal for sulfur cathode applications. They possess an amorphous, interpenetrated bulk structure consisting of a majority of intrinsic sites between two oppositely charged polymers and a minority of extrinsic sites between solution ions and polyelectrolyte backbone charges. Diffusion through the membrane is governed by the number of extrinsic sites which permits hopping of ions.
• the use of polymers as encapsulating membranes for sulfur particles provides opportunity for reducing the high polymer contents associated with sulfur/polymer composites and thus the overall capacities based on total cathode mass may be increased.
• the encapsulating membrane does not impede electronic or ionic conduction of lithium ions.
• the membrane must be comparatively thin, conformal to the encapsulating substrate and flexible to accommodate the volume changes of the sulfur core between charge and discharge.
• the final cathode structure contains a low sulfur loading of approximately 50% due to the use of the melt-infusion of sulfur into high surface area carbon.
• the resulting carbon/sulfur composite has a high content of carbon.
• sulfur loading greater than 75% by weight is required.
• Electrochemical cells and batteries containing the multi-coated anode are described and cathodes constructed of a mixture of elemental sulfur, a conductive carbon material, and a binder. Conductive polymer materials are disclosed as possible carbon constituents. However, as indicated in Example 7, the materials are mixed or blended and applied to an electrode substrate. Sub-micron sulfur particles encapsulated in conductive polymer multilayer systems as active cathode components are neither disclosed nor suggested.
• a comonomer composite containing conductive filler is described wherein the conductive filler is either present during the polymerization or is physically blended with the formed copolymer.
• Archer et al. (U.S. 2013/0330619) describes a cathode active material for a lithium-sulfur battery that is a mesoporous carbon containing infused sulfur.
• the mesoporous carbon matrix is obtained by forming a highly porous metal oxide template, fusing the metal oxide template with a carbonaceous material such as pitch and sintering.
• the metal oxide is then etched from the sintered mass leaving a mesoporous carbon into which gaseous sulfur is infused.
• the material is then milled to small size.
• Archer does not disclose or suggest sub-micron sulfur particles encapsulated in conductive polymer multilayer systems.
• Wang (U.S. 2013/0171355) describes a sulfur graphene composite material which can be employed as an active ingredient of a cathode in a lithium-sulfur battery.
• the composite is prepared by mixing a dispersion of graphene and a solution of sulfur, precipitating the sulfur onto the graphene, removing the solvents and treating the residue to form an active material.
• Li et al. (U.S. 2013/0065128) describes lithium-sulfur batteries with cathode active materials being hollow nanostructures (tubes, fibers, spheres) containing elemental sulfur and/or an active sulfur compound. According to Li, the sulfur does not occupy the entire volume of the hollow space, such that allowance is made for expansion and contraction of the sulfur material during the charging and discharging phases.
• the hollow nanostructures are first formed and then the sulfur/sulfur compound infused.
• Sub-micron sulfur particles encapsulated in conductive polymer multilayer systems as active cathode components are neither disclosed nor suggested in the description of this reference.
• Zhamu et al. (U.S. 2011/0165466) describes lithium-sulfur batteries wherein the cathode is constructed of a nano-filament web of carbon nano fibers, graphite nanofibers, carbon nanotubes, etc. Upon construction of the cell, lithium sulfide and/or lithium polysulfide is deposited on the nano-filaments and upon charge these materials convert to elemental sulfur on the cathode and lithium metal at the anode. Zhamu does not disclose or suggest cathode architecture of sub-micron sulfur particles encapsulated in conductive polymer multilayer systems.
• Naoi et al. (U.S. 2007/0287060) describes a cathode active sulfur composite of elemental sulfur and/or a compound having a sulfur-sulfur bond with microparticles of a conductive material such as carbon black (Ketjen Black).
• a mechanical composite of the sulfur and carbon black is first formed.
• the thus formed composite is heated above the melting point such that the conductive microparticles are infused into the sulfur melt which is then stressed into a fibrous form. This is cooled and pulverized and a thin uniform coating of the conductive microparticles applied to the surface of the pulverized particles.
• the thus formed composite material is the active component of a cathode for a lithium-sulfur battery.
• Choi et al. (U.S. 2005/0053718) describes a cathode material for a lithium- sulfur battery wherein particles of elemental sulfur are coated with an inorganic salt such as an alkali metal alkoxide, a borate salt, a metal oxide or a silicate. The coating is applied to the sulfur core from solution with drying.
• an inorganic salt such as an alkali metal alkoxide, a borate salt, a metal oxide or a silicate.
• Nazri et al. (U.S. 8,663,840) describes a cathode active material for a lithium- sulfur battery that consists of carbon nanotubes which contain sulfur or a sulfur compound within the hollow interior of the nanotube.
• the nanotubes are first formed and then the sulfur component placed in the hollow area by melt infusion, sublimation or solution filling followed by evaporation of the solvent.
• the exterior of the filled nanotubes is then cleaned of sulfur residue and a cathode constructed with the composite nanotubes.
• Wang et al. (CN103474633) (Abstract only) describes a complex composite and cathode structure for a lithium-sulfur battery containing the composite.
• the composite is comprised of a core of nano-carbon particles which is over coated with elemental sulfur or a polysulfide mixture.
• the nanoparticles are surface bonded with a polymeric cross-linking system and the sulfur material is incorporated in that cross-linking matrix.
• This composite is coated onto a carbon nanoparticle sulfur core-shell material.
• the mixture is coated to a substrate to form a positive electrode which is functional for a lithium-sulfur battery.
• Li et al. (Proc. Natl. Acad. Sci., 2013, 2) describes a core-shell nanoparticle having a sulfur core prepared by insitu precipitation of the sulfur in the presence of a polymer.
• a core shell nanoparticle coated with poly(3,4-ethylenedioxythiophene) (PEDOT) is described.
• an object of the present invention is to provide a sulfur composition which is suitable for utility as an electrode active material for a battery having high capacity and high cycle lifetime.
• a second object of the invention is to provide a cathode containing sulfur as an active material which is suitable for utility in a battery having high capacity and high cycle lifetime.
• a third object of the invention is to provide a lithium-sulfur battery which has sufficient capacity and lifetime to be a viable energy source for a vehicle.
• a shell comprising a first layer closest to the sulfur core of ionically charged, self-assembling conductive copolymer having at least one hydrophobic region; and at least a second conductive polymer layer having an electrical charge opposite to the first layer adjacent to and ionically bonded with the first layer;
• At least one of the core and an outer layer comprises a
• the nanoparticle comprises the functionalized carbon black and the functionalized carbon black is dispersed in the sulfur core.
• the nanoparticle comprises the functionalized carbon black and the functionalized carbon black is on or embedded in an outermost conductive polymer layer.
• the nanoparticle comprises the functionalized carbon black and the functionalized carbon black is dispersed in the sulfur core and is on or embedded in an outermost conductive polymer layer.
• the functionalized carbon comprises a carboxyl group (-COOH) as a functional component.
• the present invention provides a cathode comprising the core-shell sub-micron particle of any of the embodiments according to the present invention as an active material and in a further preferred embodiment, the present invention includes a lithium-sulfur battery comprising the cathode.
• the present invention includes a vehicle containing the lithium- sulfur battery according to the embodiments of the invention.
• Fig. 1 shows a schematic diagram for preparation of the coated encapsulated sulfur sub-micron particles according to one embodiment of the present invention.
• Fig. 2A shows a SEM image of a single coated encapsulated sulfur nanoparticle according to one embodiment of the present invention.
• Fig. 2B shows a TEM image (B) of a single coated encapsulated sulfur nanoparticle according to one embodiment of the present invention.
• Fig. 2C shows a SEM image of an aggregation of the single particles obtained in Example 1.
• Fig. 3 shows a first fixed current charge/discharge electrochemical profile for a cell constructed with single coated encapsulated nanoparticles prepared in Example 1. The cell impedance before cycling is shown in the inset.
• Fig. 4 shows a TEM image of a melting sulfur particle obtained in Example 1.
• the polymer encapsulating membrane can be observed in the inset.
• Fig. 5 shows the capacity fade over the first 500 cycles for the cell prepared in Example 1.
• Fig. 6 shows a schematic diagram for the synthesis of sub-micron sulfur particles encapsulated by a polymer membrane composed from 7 layers of
• FIG. 7 shows a SEM image of a sub-micron sulfur particle encapsulated by 7 layers of PEDOT:PSS/PDADMAC and partially decorated by functionalized Ketjen Black 600 JD carbon as described in Example 2.
• Fig. 8 shows the first fixed current charge/discharge electrochemical profile for the battery prepared in Example 2. The cell impedance before cycling is shown in the inset.
• Fig. 9 shows the capacity fade over the first 500 cycles for the battery prepared in Example 2.
• Fig. 10 shows a schematic diagram for the synthesis of sub-micron sulfur particles according to one embodiment of the present invention as described in Example 3.
• Fig. 1 1 A shows the SEM image of a single sub-micron particle obtained in Example 3.
• Fig. 1 1 B shows the TEM image of a single sub-micron sulfur particle obtained in Example 3.
• Fig. l lC shows the SEM image of an aggregate of the sub-micron particles obtained in Example 3.
• Fig. 12 shows he first fixed current charge/discharge electrochemical profile of the battery prepared in Example 3. The cell impedance before cycling is shown in the inset.
• Fig. 13 shows the capacity fade over the first 500 cycles for the battery prepared in Example 3.
• vehicle means any power driven device designed for transportation including an automobile, truck van, bus, golf cart and other utility forms of transportation.
• the inventors are directing effort and resources to the study of materials useful to produce a battery of sufficient capacity and cycle lifetime to be competitive with and replace a combustion engine as a power source as well as other utilities requiring a high capacity, high cycle lifetime battery.
• a battery suitable for large scale intermittent energy storage will also be important for storage of green energy such as provided by wind and solar generation methods.
• the inventors have studied methods to increase the sulfur density of cathodic materials.
• the use of carbon hosts conventionally employed can be eliminated and sub-micron sulfur particles can be generated in-situ from the reaction of sodium thiosulfate with an acid such as hydrochloric acid in the presence of specific polymers which encapsulate the formed sulfur particles.
• the sulfur generating reaction (Fig. 1) is conducted in the presence of polymers which contain hydrophobic and hydrophilic domains.
• the structure of the polymers governs the growth of hydrophobic sulfur near the hydrophobic domains.
• the polymer backbone rearranges in the hydrophilic medium (usually aqueous solutions) to form enclosed structures such as spheres/cubes, rhomboids, etc. which encapsulates elemental sulfur.
• polymer composition having hydrophobic and hydrophilic domains is a polymer salt of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonate (PSS).
• PEDOT poly(3,4-ethylenedioxythiophene)
• PSS polystyrene sulfonate
• conductive grade PEDOT:PSS Aldrich
• sulfur particles less than 1 micrometer in diameter (Fig.l) inside thin PEDOT:PSS shells are obtained. Since PEDOT:PSS has an overall negative charge, additional polymer layers can be adsorbed on the
• PEDOT:PSS layer (given positively charged polymers such as polydimethyldiallyl ammonium chloride (PDADMAC) are used - Fig 1). Further multiple alternating layers of oppositely charged conductive polymers may be built-up on this structure to tune the particle properties.
• PDADMAC polydimethyldiallyl ammonium chloride
• the first embodiment of the present invention provides a core-shell sub- micron particle, comprising:
• a core comprising elemental sulfur; and a shell comprising a first layer closest to the sulfur core of ionically charged, self-assembling conductive copolymer having at least one hydrophobic region; and at least a second conductive polymer layer having an electrical charge opposite to the first layer adjacent to and ionically bonded with the first layer;
• At least one of the core and surface of an outer layer comprises a functionalized conductive carbon material.
• the functionalized conductive carbon material may contain any functional group that promotes dispersion within the formed elemental sulfur core or adhesion or adsorption to the outermost ionic conductive polymer layer.
• the functionalized carbon material may be any conductive carbon material which can be functionalized for compatibility with the sub-micron particle structure and morphology according to the present invention.
• Examples of such materials include Ketjen black (carbon black), acetylene black, vapor grown carbon fiber, graphene, natural graphite, artificial graphite and activated carbon.
• the conductivity of the sub- micron sulfur core-shell particles is increased with -COOH functionalized Ketjen Black ® 600JD (Akzo Nobel Chemicals B.V.).
• the sub-micron particle comprises the functionalized carbon black and the functionalized carbon black is dispersed in the sulfur core.
• the sub-micron particle comprises the functionalized carbon black and the functionalized carbon black is on or embedded in an outermost conductive polymer layer.
• the nanoparticle comprises the functionalized carbon black and the functionalized carbon black is dispersed in the sulfur core and is on or embedded in an outermost conductive polymer layer.
• the content or amount of functionalized carbon black in the sub-micron particles may be from 0 to 5 % by weight of the total weight of the final submicron care-shell particle weight. In those embodiments wherein the functionalized carbon is present, the amount may be from 0.1 to 5 % by weight, preferably 0.25 to 3.0 weight %, and most preferably, from 0.5 to 2.5 weight %.
• the sub-micron particles obtained according to the methods described in Examples 2 and 3 and shown in Figs. 6 and 10 provide a sulfur cathodic material with very high sulfur content (>95% can be routinely obtained) and thus addresses the need identified above for higher sulfur content to obtain increased energy density.
• the elemental sub-micron sulfur particles are formed by precipitation from solution of a sulfur precursor and in one
• the obtained sulfur particles were wrapped in 7 layers of PEDOT:PSS/PDADMAC.
• the conductive hydrophobic/hydrophilic polymer employed to guide formation of the sulfur sub-micron particles were wrapped in 7 layers of PEDOT:PSS/PDADMAC.
• PEDOT:PSS carries a net negative charge and therefore, may be overcoated with a positively charged conductive polymer such as PDADMAC which is ionically attracted to the PEDOT:PSS layer. Alternating layers of opposite charge may be applied in any number to tune the properties of the particles.
• the present invention provides an electrode, preferably a cathode containing the decorated or not decorated sub-micron sulfur core-shell particles.
• a sulfur cathode may be prepared by mixing the sub-micron particles according to the above description with one or more binders and other materials conventionally employed to prepare a cathode structure. These materials may be mixed as a slurry, coated onto a metal foil, and dried.
• the methods of construction of a cathode employing an active material are conventionally known and any such method that is compatible with the decorated or not decorated sub-micron sulfur core-shell particles of the invention may be employed.
• Suitable binders known to one of ordinary skill which are chemically stable in the potential window of use of the cell may include thermoplastics and thermosetting resins.
• binders may be used independently, or mixtures may be used.
• the components may be wet blended in the presence of a suitable solvent or dry blended using a mortar or other conventionally known mixing equipment.
• the mixture may then be applied to a charge collector by conventionally known methods.
• Any suitable charge collector may be employed.
• Preferred charge collectors may be any of carbon, stainless steel, nickel, aluminum and copper.
• the cathode thus prepared may be employed in the construction of an electrochemical cell or battery in a conventionally known manner.
• the cathode may be combined with an anode having lithium as an active material.
• the present invention provides a lithium-sulfur battery comprising a lithium anode and a cathode comprising the decorated or not decorated sub-micron sulfur core-shell particles according to the present invention.
• Nonaqueous solvents suitable as an electrolyte include cyclic carbonates, chain carbonates, cyclic esters, cyclic ethers and chain ethers.
• a cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate.
• a chain carbonate include dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.
• a cyclic ester carbonate include gamma butyrolactone and gamma valerolactone.
• Examples of a cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran.
• a chain ether include dimethoxy ethane and ethyleneglycol dimethyl ether.
• the lithium electrolyte ion or mobile ion carrier may be any conventionally known to one of skill in the art and may include one or more of LiPF 6 , LiC10 4 , LiAsF 6 , LiBF 4 , LiN(CF 3 S0 2 ) 2 , Li(CF 3 S0 3 ) and LiN(C 2 F 5 S0 2 ) 2 .
• the present invention includes a vehicle containing a lithium-sulfur battery according to the present invention wherein the vehicle includes an automobile, truck van, bus, golf cart and other utility forms of transportation.
• Fig. 1 in the presence of conductive grade PEDOT:PSS (Aldrich). Sulfur particles less than 1 micrometer in diameter were obtained (figure 2) inside thin PEDOT:PSS shells. A sulfur material with very high sulfur content (>95%) was obtained.
• PEDOT:PSS coated sulfur particles (50% sulfur in final cathode) was constructed.
• the electrochemical response of the battery at a high rate of 2C is shown in Fig 3.
• the thin polymer coating ( ⁇ 3nm, Fig. 4) permitted battery operation over 500 cycles (Fig.
• Example 2 Encapsulated Sulfur Particles with modified Carbon on surface.
• Sub-micron sulfur particles were prepared in the presence of conductive grade PEDOT:PSS (Aldrich), as described in Fig. 6. The obtained sulfur particles were less than 1 micrometer in diameter and were encapsulated inside thin PEDOT:PSS shells. Since PEDOT:PSS has an overall negative charge, a layer of positively charged poly(dimethyldiallyl ammonium chloride) (PDADMAC) was adsorbed on the conductive grade PEDOT:PSS (Aldrich), as described in Fig. 6. The obtained sulfur particles were less than 1 micrometer in diameter and were encapsulated inside thin PEDOT:PSS shells. Since PEDOT:PSS has an overall negative charge, a layer of positively charged poly(dimethyldiallyl ammonium chloride) (PDADMAC) was adsorbed on the PDADMAC.
• PDADMAC poly(dimethyldiallyl ammonium chloride)
• a 2032 coin cell battery having a lithium metal anode and a cathode containing the functionalized carbon coated sub-micron sulfur particles wrapped in a polymer membrane composed from 7 layers of PEDOT:PSS/PDADMAC (50% sulfur in final cathode) was then prepared and evaluated for performance.
• the electrochemical response of the battery at a high rate of 2C is shown in Fig. 8.
• the 7 layer polymer coating caused a high impedance of ⁇ 300 Ohm.cm and high hysteresis (higher than IV) between charge and discharge (inset in Fig. 8) but the charge/discharge efficiency was nearly 100% (Fig. 9) and no overcharging due to polysulfide dissolution was visible in the first discharge cycle.
• the capacity was ⁇ 750 rriAh/g sulfur.
• the battery was cycled for over 500 cycles (Fig. 9).
• Sub-micron sulfur particles were prepared in a reaction mixture containing -COOH functionalized Ketjen Black 600 JD in the presence of conductive grade
• PEDOT:PSS Aldrich
• the obtained sulfur particles containing the functionalized carbon were less than 1 micrometer in diameter and were encapsulated inside thin PEDOT:PSS shells. Since PEDOT:PSS has an overall negative charge, a layer of positively charged poly(dimethyldiallyl ammonium chloride) (PDADMAC) was adsorbed on the PEDOT:PSS shells. The application of alternating PEDOT:PSS shell/ PDADMAC coating was repeated until a total of seven layers was obtained. COOH functionalized Ketjen Black 600JD was then applied to the outer surface of the sulfur/polymer spheres in minimum amounts and with intimate contact (Fig. 10).
• PDADMAC poly(dimethyldiallyl ammonium chloride)
• Fig. 1 1 A and B show the SEM image and TEM image of a single sub-micron sulfur particle encapsulated by 7 layers of PEDOTrPSS/PDADMAC and partially covered with functionalized Ketjen Black 600 JD carbon that was obtained.
• Fig. 11C shows an aggregation of these particles.
• a 2032 coin cell battery having a lithium metal anode and a cathode containing the functionalized carbon both within the sulfur core and coated on the polymer membrane composed from 7 layers of PEDOT:PSS/PDADMAC (50% sulfur in final cathode) was then prepared and evaluated for performance.
• the electrochemical response of the battery at a high rate of 2C is shown in Fig. 12.
• the battery was cycled for over 500 cycles (Fig. 13).
• PVDF/NMP polyvinylidene fluoride/n-Methyl-2-pyrrolidone
• the electrolyte used in electrochemical cells was composed of 1M LiTFSI salt (purchased from 3M) in a 1 : 1 mixture of anhydrous 1,3-dioxolane (Sigma Aldrich) and 1 ,2-dimethoxyethane (Sigma Aldrich).
• Electrochemistry Working electrodes were prepared by casting a 80 ⁇ slurry containing the coated sulfur particles from the Examples above, 20% SuperP Li and 3% PVDF binder diluted as needed with NMP/cyclopentanone on a 12 ⁇ Al foil current collector. The total cathode weight was maintained at approximately 3mg. The electrodes were dried at 60° C for 24 hours and then transferred inside the Ar-filled glove box for coin cell assembly. Lithium metal foil (1mm thick) was used as the anode. 2032 stainless steel coin cells with a Celgard 2325 separator were used for electrochemical measurements. Charge and discharge rates were calculated assuming theoretical capacity for the total amount of sulfur in the cathode. BioLogic SAS, model VMP3, multi-channel Science Instruments potentiostats were used for electrochemical measurements. Data was processed with EC-Lab Software VI 0.02 with the corresponding VMP3 firmware, provided by Science Instruments.

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