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
  • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
  • H01M10/39—Accumulators not provided for in groups H01M10/05-H01M10/34 working at high temperature
  • H01M10/399—Cells with molten salts
• • 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
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
• • 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
  • H01M4/381—Alkaline or alkaline earth metals elements
• • 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
  • H01M4/582—Halogenides
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
  • H01M4/662—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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/70—Carriers or collectors characterised by shape or form
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/70—Carriers or collectors characterised by shape or form
  • H01M4/72—Grids
  • H01M4/74—Meshes or woven material; Expanded metal
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/70—Carriers or collectors characterised by shape or form
  • H01M4/80—Porous plates, e.g. sintered carriers
  • H01M4/808—Foamed, spongy materials
• • 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
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0048—Molten electrolytes used at high temperature
  • H01M2300/0054—Halogenides
• • 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
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0048—Molten electrolytes used at high temperature
  • H01M2300/0054—Halogenides
  • H01M2300/0057—Chlorides
• • 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
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0065—Solid electrolytes
  • H01M2300/0068—Solid electrolytes inorganic
• • 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 disclosed invention relates to an intermediate temperature, sodium - halogen secondary cell (or rechargeable battery) with a sodium ion conductive electrolyte membrane and a positive electrolyte that comprises one or more sodium haloaluminate salts and a sodium halide.
• the battery system utilizes a molten eutectic mixture of sodium haloaluminate salts having a relatively low melting point.
• Batteries are known devices that are used to store and release electrical energy for a variety of uses. In order to produce electrical energy, batteries typically convert chemical energy directly into electrical energy. Generally, a single battery includes one or more galvanic cells, wherein each of the cells is made of two half-cells that are electrically isolated except through an external circuit. During discharge, electrochemical reduction occurs at the cell's positive electrode, while electrochemical oxidation occurs at the cell's negative electrode. While the positive electrode and the negative electrode in the cell do not physically touch each other, they are generally chemically connected by at least one (or more) ionically conductive and electrically insulative electrolytes, which can either be in a solid state, a liquid state, or in a combination of such states. When an external circuit, or a load, is connected to a terminal that is connected to the negative electrode and to a terminal that is connected to the positive electrode, the battery drives electrons through the external circuit, while ions migrate through the electrolyte.
• Batteries can be classified in a variety of manners. For example, batteries that are completely discharged only once are often referred to as primary batteries or primary cells. In contrast, batteries that can be discharged and recharged more than once are often referred to as secondary batteries or secondary cells. The ability of a cell or battery to be charged and discharged multiple times depends on the Faradaic efficiency of each charge and discharge cycle.
• rechargeable batteries based on sodium can comprise a variety of materials and designs, most, if not all, sodium batteries that require a high Faradaic efficiency employ a solid primary electrolyte separator, such as a solid ceramic primary electrolyte membrane.
• a solid primary electrolyte separator such as a solid ceramic primary electrolyte membrane.
• the principal advantage of using a solid ceramic primary electrolyte membrane is that the Faradaic efficiency of the resulting cell approaches 100%. Indeed, in almost all other cell designs, electrode solutions in the cell are able to intermix over time and, thereby, cause a drop in Faradaic efficiency and loss of battery capacity.
• the primary electrolyte separators used in sodium batteries that require a high Faradaic efficiency often consist of ionically conductive polymers, porous materials infiltrated with ionically conductive liquids or gels, or dense ceramics.
• many rechargeable sodium batteries that are presently available for commercial applications comprise a molten sodium metal negative electrode, a sodium ⁇ ''-alumina ceramic electrolyte separator, and a molten positive electrode, which may include a composite of molten sulfur and carbon (called a sodium/sulfur cell).
• sodium-based rechargeable batteries may have significant shortcomings.
• the sodium ⁇ "-alumina ceramic electrolyte separator is typically more conductive and is better wetted by molten sodium at a temperature in excess of about 270° C and/or because the molten positive electrode typically requires relatively high temperatures (e.g., temperatures above about 170° or 180° C) to remain molten
• many conventional sodium-based rechargeable batteries operate at temperatures higher than about 270° C and are subject to significant thermal management problems and thermal sealing issues.
• some sodium-based rechargeable batteries may have difficulty dissipating heat from the batteries or maintaining the negative electrode and the positive electrode at the relatively high operating temperatures.
• the relatively high operating temperatures of some sodium-based batteries can create significant safety issues.
• the relatively high operating temperatures of some sodium-based batteries require their components to be resistant to, and operable at, such high temperatures. Accordingly, such components can be relatively expensive.
• such batteries can be expensive to operate and energy inefficient.
• Examples of sodium-halogen secondary cells are disclosed in Applicant's copending U.S. Patent Application No. 14/019,651, published as U.S. Publication No. 2014/0065456 entitled "Sodium-Halogen Secondary Cell.”
• the disclosed secondary cells include a positive electrode compartment housing a current collector disposed in a liquid positive electrode solution.
• suitable positive electrode solution materials include organic solvents such as dimethyl sulfoxide, NMF (N-methylformamide), and ionic liquids.
• the present disclosure provides an improvement to the positive electrode solution of the sodium-halogen secondary cells disclosed in Applicant's copending application. More specifically, the disclosed invention utilizes a positive electrolyte that comprises sodium halide in a molten haloaluminate electrolyte. In some disclosed embodiments, the battery system utilizes a molten eutectic mixture of sodium haloaluminate salts having a relatively low melting point.
• a sodium ion conductive solid electrolyte separates the negative electrode and the positive electrode.
• the sodium ion conductive solid electrolyte comprises a NaSICON electrolyte material.
• the NaSICON electrolyte material has high sodium conductivity at cell operating temperatures.
• the battery operates at a temperature in the range from 80 °C to 210 °C.
• the rechargeable sodium-halogen battery includes a negative electrode comprising metallic sodium in molten state.
• the negative electrode may comprise metallic sodium in a solid state.
• the positive electrode comprises NaX, where X is a halogen selected from CI, Br and I.
• the positive electrode is disposed in a molten salt positive electrolyte comprising AIX 3 .
• the positive electrolyte is a mixture of at least two AIX 3 salts that can be represented by the formula where 0 ⁇ ⁇ ⁇ 4, wherein X' and X" are different halogens selected from CI, Br and I.
• the mixed molten salt positive electrolyte comprises at least two salts of the general formula NaAlX'4 and NaAlX" 4 at various molar ratios, wherein X' and X" are different halogens selected from CI, Br and I.
• the molar ratio of NaAlX'4 to NaAlX" 4 is in the range of 9:1 to 1 :9 with corresponding ⁇ values of 0.4 to 3.6.
• the positive electrode comprises additional NaX or a mixture of NaX compounds added in a molar ratio to the mixed molten salt positive electrolyte ranging from 1 :1 to 3 : 1 of NaX : NaAlX sX'
• the excess NaX renders the positive electrolyte highly basic.
• the positive electrode and mixed molten salt positive electrolyte is a molten liquid or a two phase mixture wherein the mixed molten salt positive electrolyte is predominantly a liquid phase and the additional NaX or mixture of NaX compounds is a solid phase.
• the positive electrode is disposed in a mixed molten salt positive electrolyte comprising at least three salts that can be represented by the formula NaAlX' 4 _ 5 _ ro X" 5 X'" ro , where X', X" and X' " are three different halogens selected from CI, Br, and I, where 0 ⁇ ⁇ ⁇ 4, 0 ⁇ in ⁇ 4, and 0 ⁇ ⁇ + ⁇ ⁇ 4.
• the mixed molten salt positive electrolyte comprises NaAlCl 4 , NaAlBr 4 , and NaAlI 4 , at various molar ratios.
• Fig. 1 depicts a schematic diagram of a representative embodiment of a molten sodium-halogen secondary cell, wherein the cell is in the process of being discharged.
• Fig. 2 depicts a schematic diagram of a representative embodiment of the molten sodium-halogen secondary cell, wherein the cell is in the process of being recharged.
• Fig. 3 A depicts one potential reaction, designated Battery Chemistry 1 , at the positive current collector.
• Fig. 3B depicts another potential reaction, designated Battery Chemistry 2, at the positive current collector.
• Fig. 4 is a graph comparing the conductivity of Nal in a molten salt electrolyte and in an organic solvent as a function of temperature.
• Figs. 5A and 5B are graphs comparing the oxidation of iodide in a sodium-iodine secondary cell containing Nal in A1C1 3 at basic and acidic ratios of NaI:AlCl 3 .
• Fig. 6 is a graph of the current vs. voltage for the operation of the symmetrical cells described in Example 3.
• the present embodiments provide a sodium-halogen secondary cell, which includes a molten or solid state sodium negative electrode and a sodium halide positive electrode disposed in a molten positive electrolyte that comprises one or more haloaluminate salts.
• the secondary cell utilizes a molten eutectic mixture of sodium haloaluminate salts having a relatively low melting point.
• Figure 1 shows a representative embodiment in which the sodium secondary cell 10 comprises a negative electrode compartment 15 that includes a sodium metal negative electrode 20 and a positive electrode compartment 25 that comprises a sodium halide positive electrode.
• the positive electrode includes a current collector 30 disposed in a positive electrolyte 35 comprising one or more molten haloaluminate salts (AICI 3 , AlBr 3 , and A1I 3 ).
• a sodium ion conductive electrolyte membrane 40 separates the negative electrode from the positive electrode and positive electrolyte 35.
• the sodium ion conductive electrolyte membrane 40 separates a first terminal 45 from a second terminal 50.
• Figure 1 illustrates that as the cell 10 is discharged and electrons (e ) flow from the negative electrode 20 (e.g., via the first terminal 45), sodium is oxidized from the negative electrode 20 to form sodium ions (Na + ).
• Figure 1 shows that these sodium ions are respectively transported from the sodium negative electrode 20, through the sodium ion conductive membrane 40, and to the positive electrolyte 35.
• Figure 2 shows that as the secondary cell 10 is recharged and electrons (e ) flow into the sodium negative electrode 20 from an external power source (not shown), such as a recharger, the chemical reactions that occurred when the cell 10 was discharged (as shown in Figure 1) are reversed.
• Figure 2 shows that as the cell 10 is recharged, sodium ions (Na + ) are respectively transported from the positive electrolyte 35, through the electrolyte membrane 40, and to the negative electrode 20, where the sodium ions are reduced to form sodium metal (Na).
• the cell can comprise a negative electrode compartment 15 and a positive electrode compartment 25.
• the two compartments can be any suitable shape and have any other suitable characteristic that allows the cell 10 to function as intended.
• the negative electrode and the positive electrode compartments can be tubular, rectangular, or be any other suitable shape.
• the two compartments can have any suitable spatial relationship with respect to each other.
• FIG. 2 shows that the negative electrode compartment 15 and the positive electrode compartment 25 can be adjacent to each other, in other embodiments (not shown), one compartment (e.g., the negative electrode compartment) is disposed, at least partially, in the other compartment (e.g., the positive electrode compartment), while the contents of the two compartments remain separated by the electrolyte membrane 40 and any other compartmental walls.
• one compartment e.g., the negative electrode compartment
• the other compartment e.g., the positive electrode compartment
• the cell 10 can comprise any suitable sodium negative electrode 20 that allows the cell 10 to function (e.g., be discharged and recharged) as intended.
• suitable sodium negative electrode materials include, but are not limited to, a sodium sample that is substantially pure and a sodium alloy comprising any other suitable sodium-containing negative electrode material.
• the negative electrode comprises or consists of an amount of sodium that is substantially pure. In such embodiments, because the melting point of pure sodium is around 98° C, the sodium negative electrode will become molten above that temperature.
• the positive electrode compartment 25 can comprise any suitable positive electrode that allows the cell to be charged and discharged as intended.
• the positive electrode can comprise virtually any current collector 30 in combination with a halogen, shown generically as "X" in Figs. 1 and 2, in a positive electrolyte 35 comprising one or more sodium haloaluminate salts.
• the current collector 30 can be disposed in any suitable location in the positive electrode compartment 25 that allows the cell 10 to function as intended.
• the cell 10 can comprise any suitable current collector that allows the cell to be charged and discharged as intended.
• the current collector can comprise virtually any current collector configuration that has been successfully used in a sodium-based rechargeable battery system.
• the current collector comprises at least one of wires, felts, foils, plates, parallel plates, tubes, meshes, mesh screens, foams, and/or other suitable current collector configuration.
• the foam may include, without limitation, metal foams and carbon foams.
• the current collector comprises a configuration having a relatively large surface area which may include one or more mesh screens and metal foams.
• the current collector 30 can comprise any suitable material that allows the cell 10 to function as intended.
• suitable current collector materials include tungsten, stainless steel, carbon, molybdenum, titanium, platinum, copper, nickel, zinc, a sodium intercalation material (e.g., Na x Mn0 2 , etc.), nickel foam, nickel, a sulfur composite, a sulfur halide (e.g., sulfuric chloride), and/or another suitable material.
• these materials may coexist or exist in combinations.
• the current collector comprises tungsten, carbon, molybdenum, titanium.
• the reactions that may occur at the negative electrode 20, the positive electrode/current collector 30, and the overall reaction as the cell 10 is discharged may occur in at least two steps. These two potential reactions are shown below and designated Battery Chemistry 1 (shown schematically in Fig. 3A for battery recharge) and Battery Chemistry 2 (shown schematically in Fig. 3B for battery recharge). It has been observed that these reactions may be individual steps of a multi-step reaction, or depending upon the battery conditions, one step may be favored over another step.
• X comprises iodine, bromine, or chlorine.
• the cell 10 may have the following chemical reactions and the following theoretical voltage (V vs. SHE (standard hydrogen electrode)) and theoretical specific energy (Wh/kg):
• the charging reactions at the positive electrode may occur in two steps: 1) iodide to triiodide and 2) triiodide to iodine.
• discharging reactions at the positive electrode may occur in two steps: 1) iodine to triiodide and 2) triiodide to iodide.
• the charging and discharging reactions may occur using the combination of reaction chemistries above.
• the cell 10 may have the following chemical reactions and the following theoretical voltage (V vs. SHE) and theoretical specific energy (Wh/kg):
• the charging reactions at the positive electrode may occur in two steps: 1) bromide to tribromide and 2) tribromide to bromine.
• discharging reactions at the positive electrode may occur in two steps: 1) bromine to tribromide and 2) tribromide to bromide.
• the charging and discharging reactions may occur using the combination of reaction chemistries above.
• an alternative positive electrode chemistry may include:
• the membrane can comprise any suitable material that selectively transports sodium ions and permits the cell 10 to function with a positive electrolyte 35.
• the electrolyte membrane comprises a NaSICON-type (sodium Super Ion CONductive) material.
• the NaSICON-type material may comprise any known or novel NaSICON-type material that is suitable for use with the described cell 10.
• the NaSICON-type membrane comprises Na 3 Si 2 Zr 2 POi 2 .
• the NaSICON-type membrane comprises one or more NaSELECi® materials, produced by Ceramatec, Inc. in Salt Lake City, Utah.
• the positive electrode comprises NaX, where X is a halogen selected from CI, Br and I.
• the positive electrode is preferably NaT
• the positive electrode is disposed in a molten salt positive electrolyte comprising A1X 3 .
• NaX and A1X 3 may combine to form NaAlX 4 as follows:
• the positive electrode is combined with a mixture of at least two A1X 3 salts.
• the combination of positive electrode and positive electrolyte can be represented by the general formula where 0 ⁇ ⁇ ⁇ 4, wherein X' and X" are different halogens selected from CI, Br and I.
• the mixed molten salt positive electrolyte comprises at least two salts of the general formula NaAlX' 4 and NaAlX" 4 at various molar ratios, wherein X' and X" are different halogens selected from CI, Br and I.
• the molar ratio of NaAlX' 4 to NaAlX" 4 is in the range of 9: 1 to 1 :9 with corresponding ⁇ values of 0.4 to 3.6.
• the positive electrode comprises additional NaX or a mixture of NaX compounds added in a molar ratio to the mixed molten salt positive electrolyte ranging from 1 : 1 to 3 : 1 of NaX : NaAlX sX'
• the excess NaX renders the positive electrolyte highly basic.
• the positive electrode and mixed molten salt positive electrolyte is a molten liquid or a two phase mixture wherein the mixed molten salt positive electrolyte is predominantly a liquid phase and the additional NaX or mixture of NaX compounds is a solid phase.
• the positive electrode is disposed in a mixed molten salt positive electrolyte comprising at least three salts that can be represented by the formula NaAlX' 4 _ 5 _ ro X" 5 X"' ro , where X', X" and X' " are three different halogens selected from CI, Br, and I, where 0 ⁇ ⁇ ⁇ 4, 0 ⁇ in ⁇ 4, and 0 ⁇ ⁇ + ⁇ ⁇ 4.
• the mixed molten salt positive electrolyte comprises NaAlCl 4 , NaAlBr 4 , and NaAlI 4 , at various molar ratios.
• the positive electrolyte 35 also comprises one or more halogens and/or halides.
• the halogens and halides, as well polyhalides and/or metal halides that form therefrom can perform any suitable function, including, without limitation, acting as the positive electrode as the cell 10 operates.
• suitable halogens include bromine, iodine, and chlorine.
• suitable halides include bromide ions, polybromide ions, iodide ions, polyiodide ions, chloride ions, and polychloride ions. While the halogens/halides can be introduced into the positive electrode solution in any suitable manner, in some embodiments, they are added as NaX, wherein X is selected from Br, I, CI, etc.
• the cell 10 can comprise any suitable terminals that are capable of electrically connecting the cell with an external circuit (not shown), including without limitation, to one or more cells.
• the terminals can comprise any suitable material, be of any suitable shape, and be of any suitable size.
• the cell 10 can optionally comprise any other suitable component.
• Figures 1 and 2 show an embodiment in which the cell 10 comprises a heat management system 55, 60. Independent heat management systems may be associated with the negative electrode and positive electrode compartments. Alternatively, a single heat management system may be disposed in only one compartment or to the exterior of the cell 10 generally.
• the cell can comprise any suitable type of heat management system that is capable of maintaining the cell within a suitable operating temperature range. Some examples of such heat management systems include, but are not limited to, a heater, a cooler, one or more temperature sensors, and appropriate temperature control circuitry.
• the described cell 10 may function at any suitable operating temperature.
• the sodium negative electrode and the positive electrolyte may have any suitable temperature.
• the negative and positive electrode compartments may operate at the same or different temperatures.
• the cell functions at an intermediate operating temperature in the range from about 80 °C to about 210 °C.
• the cell may function at an intermediate operating temperature in the range from about 1 10 °C to about 180 °C.
• the operating temperature of the cell in the range of about 150 °C to about 170 °C.
• the conductivity of Nal in a molten salt positive electrolyte AICI 3 was compared to the conductivity of Nal in an organic solvent solution that included N-methyl formamide.
• the molten salt positive electrolyte had a general formula of NaAl x I y Cl z .
• the conductivity of Nal in a molten salt positive electrolyte was approximately three times the conductivity of the organic solvent-based electrolyte at 120 °C, as shown in Fig. 4. Cells utilizing a molten salt positive electrolyte will be more energy dense due to higher molarity of Nal. Furthermore, cells utilizing a molten salt positive electrolyte are safer than organic solvent based positive electrolyte solutions because if molten sodium happens to contact the molten salt positive electrolyte, the chemical reaction would only produce non-flammable salts.
• a sodium-iodine secondary cell was prepared as described herein containing sodium iodide in molten AICI 3 in a 60:40 NaI:AlCl 3 ratio (a "basic" electrolyte). Tungsten wire was used as the positive current collector. NaSICON was used to separate a molten sodium negative electrode from the positive electrode/positive electrolyte. The oxidation of iodide was measured and found to produce two oxidation peaks, consistent with Battery Chemistry 1 and Battery Chemistry 2, described herein. Experimental results are shown in Fig. 5A. The oxidation peaks were found to be reversible.
• FIG. 6 A graph of the current vs. voltage for the operation of the symmetrical cells is shown in Fig. 6. Because there is little or no hysteresis shown in Fig. 6, it may be concluded that the oxidation / reduction reactions that occur in the positive electrode / positive electrolyte are highly reversible.

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• 2015
  • 2015-12-01 WO PCT/US2015/063244 patent/WO2016089902A1/en not_active Ceased
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