| Lithium-sulphur battery with high specific energy -> Monitor Keywords |
|
|
 
Lithium-sulphur battery with high specific energyRelated Patent Categories: Chemistry: Electrical Current Producing Apparatus, Product, And Process, Current Producing Cell, Elements, Subcombinations And Compositions For Use Therewith And Adjuncts, Electrode, Chemically Specified Inorganic Electrochemically Active Material ContainingLithium-sulphur battery with high specific energy description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070072076, Lithium-sulphur battery with high specific energy. Brief Patent Description - Full Patent Description - Patent Application Claims
PRIOR APPLICATION DATA [0001] The present application claims benefit from prior U.S. provisional patent application No. 60/734,320, filed Nov. 8, 2005, entitled "LITHIUM-SULPHUR BATTERY WITH HIGH SPECIFIC ENERGY", from prior U.S. provisional patent application No. 60/721,062, filed Sep. 28, 2005, entitled "LITHIUM-SULPHUR BATTERY WITH HIGH SPECIFIC ENERGY", and from UK patent application no. 0519491.5, filed Sep. 26, 2005 each of which being incorporated by reference herein in its entirety. FIELD OF THE INVENTION [0002] The present invention relates to electrochemical power engineering, in particular it relates to chemical sources of electric energy (cells or batteries) comprising negative electrodes made of alkali metals and positive electrodes comprising sulphur and/or sulphur-based non-organic or organic (including polymeric) compounds as an electrode depolarizer substance. BACKGROUND [0003] The lithium-sulphur electrochemical system has a high theoretical specific energy of 2600 Wh/kg (D. Linden, T. B. Reddy, Handbook of batteries, third ed., McGraw-Hill, New-York, 2001), and is therefore of great interest at present. Specific energy is defined as the ratio of the energy output of a cell or battery to its weight, and is expressed in Wh/kg. The term specific energy is equivalent to the term gravimetric energy density. [0004] It has been proposed to use various materials as a depolarizer substance for the positive electrode in lithium-sulphur batteries: elemental sulphur (U.S. Pat. No. 5,789,108; U.S. Pat. No. 5,814,420), sulphur-organic compounds (U.S. Pat. No. 6,090,504), sulphur-containing polymers (U.S. Pat. No. 6,201,100; U.S. Pat. No. 6,174,621; U.S. Pat. No. 6,117,590), and solutions of sulphur or lithium polysulphides in aprotic electrolyte systems (Rauh R. D., Abraham K. M., Pearson G. F., Surprenant J. K., Brummer S. B.: "A lithium/dissolved sulphur battery with an organic electrolyte", J. Electrochem. Soc. 1979, vol. 126, no. 4, pp 523-527; Yamin H., Peled E.: "Electrochemistry of a nonaqueous lithium/sulphur cell", J. of Power Sources, 1983, vol. 9, pp 281-287). [0005] Solutions of lithium salts in aprotic dipolar solvents (typically linear or cyclic ethers) or their mixtures have been used as electrolytes in lithium-sulphur batteries (Yamin H., Penciner J., Gorenshtain A., Elam M., Peled E.: "The electrochemical behavior of polysulphides in tetrahydrofuran", J. of Power Sources, 1985, vol. 14, pp 129-134; Yamin H., Gorenshtein A., Penciner J., Sternberg Y., Peled E.: "Lithium sulphur battery oxidation/reduction mechanisms of polysulphides in THF solution", J. Electrochem. Soc., 1988, vol 135, no. 5, pp 1045-1048; Duck-Rye Chang, Suck-Hyun Lee, Sun-Wook Kim, Hee-Tak Kim: "Binary electrolyte based on tetra(ethylene glycol) dimethyl ether and 1,3-dioxolane for lithium-sulphur battery", J. of Power Sources, 2002, vol. 112, pp 452-460). [0006] The practical specific energy of a typical chemical source of electric energy usually reaches 20-30% of the theoretical maximum value of the specific energy of the electrochemical system that is employed. This is because various auxiliary elements (the separator, the current collectors of the electrodes, the electrolyte and other components) of the battery contribute to its total weight in addition to the electrode depolarizers. The auxiliary elements of the battery design do not themselves take part in the electrochemical reaction itself, but are provided so as to facilitate the reaction process and to promote normal functioning of the battery. [0007] The value of the practical specific energy for laboratory lithium-sulphur cells generally reaches only 10-15% of its theoretical value, and is typically around 250-350 Wh/kg (J. Broadhead, T. Skotheim: "A safe, fast-charge, two-volt lithium/polymer cathode `AA`-size cell with a greater than 250 Wh kg-1 energy density", Journal of Power Sources, 65 (1997), 1-2, 213-218; Peled E., Gorenshtein A., Segal M., Sternberg Y.: "Rechargeable lithium-sulphur battery (extended abstract)", J. of Power Sources, 1989, vol. 26, pp 269-271). SUMMARY [0008] Disregarding the weight of the auxiliary battery elements, the difference between the theoretical and the practical values for the specific energies of laboratory lithium-sulphur cells is due to insufficient utilization of the positive electrode depolarizer (sulphur or sulphur-based compounds) and the excess quantity of electrolyte that is generally provided. [0009] Embodiments of the present invention seek at least substantially to optimize the electrolyte quantity in lithium-sulphur cells, and thereby to improve their practical specific energy. [0010] One embodiment includes a chemical source of electric energy comprising a positive electrode (cathode) including sulphur or sulphur-based organic compounds, sulphur-based polymeric compounds or sulphur-based inorganic compounds as a depolarizer, a negative electrode (anode) made of metallic lithium or lithium-containing alloys, and an electrolyte comprising a solution of at least one salt in at least one aprotic solvent, the chemical source of electric energy being configured to generate soluble polysulphides in the electrolyte during a first stage of a two stage discharge-process, characterised in that the quantity of sulphur in the depolariser and the volume of electrolyte are selected such that, after first stage discharge of the cathode, the concentration of the soluble polysulphides in the electrolyte is at least 70% of a saturation concentration of the polysulphides in the electrolyte. [0011] In another embodiment the quantity of sulphur in the depolariser and the volume of electrolyte are selected such that, after complete discharge of the cathode, the concentration of the soluble lithium polysulphides in the electrolyte is from 70 to 90% of a saturation concentration of the polysulphides in the electrolyte. [0012] In another embodiment the depolarizer includes sulphur, carbon black and polyethylene oxide. [0013] In another embodiment the electrolyte includes a solution of one or several lithium salts selected from the group consisting of: lithium trifluoromethanesulphonate, lithium perchlorate, lithium trifluoromethanesulfonimide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrachloroaluminate, tetraalkylammonium salt, lithium chloride, lithium bromide and lithium iodide; in one or several solvents selected from the group consisting of: dioxolane, tetrahydrofuran, dimethoxyethane, diglyme, triglyme, tetraglyme, dialkyl carbonates, sulfolane and butyrolactone. BRIEF DESCRIPTION OF THE DRAWINGS [0014] For a better understanding of the present invention and to show how it may be carried into effect, reference shall now be made by way of example to the accompanying drawing, in which: [0015] FIG. 1 is a plot showing the two stage discharge process of a lithium-sulphur battery of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0016] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. [0017] The specific energy of a chemical source of electric energy is determined by the theoretical specific energy of the selected electrochemical system, as well as by the weight of auxiliary components required to ensure the proper operation of the chemical source of electric energy (e.g. a separator, current collectors of electrodes, a binder, current conducting additives, an electrolyte and other components), and also by the degree (efficiency) of utilization of the depolarizer. The weight of the auxiliary components generally makes up 70-80% of the total weight of the cell. In order to achieve improved specific energy characteristics, the weight of the auxiliary components must be reduced. [0018] The weight of the electrolyte is a significant part of the total weight of the chemical source of electric energy. The electrolyte performs supplementary functions in chemical sources of electric energy with solid depolarizers, for example supporting the electrochemical reaction process and providing ion transport between the electrodes. Therefore in such systems it is desirable to minimize the quantity of the electrolyte. Continue reading about Lithium-sulphur battery with high specific energy... Full patent description for Lithium-sulphur battery with high specific energy Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Lithium-sulphur battery with high specific energy patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Lithium-sulphur battery with high specific energy or other areas of interest. ### Previous Patent Application: Lithium secondary battery, negative electrode therefor, and method of their manufacture Next Patent Application: Hydrogen-absorbing alloy electrode, alkaline storage battery, and method of manufacturing the alkaline storage battery Industry Class: Chemistry: electrical current producing apparatus, product, and process ### FreshPatents.com Support Thank you for viewing the Lithium-sulphur battery with high specific energy patent info. IP-related news and info Results in 0.6684 seconds Other interesting Feshpatents.com categories: Daimler Chrysler , DirecTV , Exxonmobil Chemical Company , Goodyear , Intel , Kyocera Wireless , 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
