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Oligo phosphate-based electrode active materials and methods of making sameRelated Patent Categories: Compositions, Electrically Conductive Or Emissive Compositions, Metal Compound ContainingOligo phosphate-based electrode active materials and methods of making same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060091363, Oligo phosphate-based electrode active materials and methods of making same. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation of U.S. Ser. No. 10/409,849, filed Apr. 8, 2003, now allowed. FIELD OF THE INVENTION [0002] This invention relates to oligo phosphate-based materials usable as electrode active materials, methods for making such materials, and electrochemical cells employing such materials. BACKGROUND OF THE INVENTION [0003] A battery consists of one or more electrochemical cells, wherein each cell typically includes a positive electrode, a negative electrode, and an electrolyte or other material for facilitating movement of ionic charge carriers between the negative electrode and positive electrode. As the cell is charged, cations migrate from the positive electrode to the electrolyte and, concurrently, from the electrolyte to the negative electrode. During discharge, cations migrate from the negative electrode to the electrolyte and, concurrently, from the electrolyte to the positive electrode. [0004] Such batteries generally include an electrochemically active material having a crystal lattice structure or framework from which ions can be extracted and subsequently reinserted, and/or permit ions to be inserted or intercalated and subsequently extracted. [0005] In general, positive electrode active materials should exhibit a high free energy of reaction with the cation (e.g. Li.sup.+, Na.sup.+, and the like), be able to release and insert a large quantity of cations, maintain its lattice structure upon insertion and extraction of cations, allow rapid diffusion of cations, afford good electrical conductivity, be not significantly soluble in the electrolyte system of the battery, and be readily and economically produced. [0006] Unfortunately, many existing electrode materials are not economical to produce, afford insufficient voltage, have insufficient charge capacity, or lose their ability to be recharged over multiple cycles. Therefore, there is a current need for an electrode active material that exhibits greater charge capacity, is economical to produce, affords sufficient voltage, and retains capacity over multiple cycles. SUMMARY OF THE INVENTION [0007] The invention provides novel alkali-metal containing oligo phosphate electrode active materials represented by the general nominal formula, A.sub.aM.sub.bX.sub.cO.sub.(3c+1), [0008] wherein: [0009] (a) A is at least one alkali metal, and 0<a.ltoreq.6; [0010] (b) M is at least one redox active element, wherein 1.ltoreq.b.ltoreq.4; [0011] (c) X is selected from the group consisting of P, As, Sb, Si, Ge, V, S, and mixtures thereof; and [0012] (d) 2.ltoreq.c.ltoreq.5; wherein A, M, X, a, b and c are selected so as to maintain electroneutrality of the material. [0013] This invention also provides electrodes which utilize the electrode active material of this invention. Also provided are batteries that include a first electrode having an electrode active material of this invention; a second electrode having a compatible active material; and an electrolyte. In one embodiment, the novel electrode material of this invention is used as a positive electrode (cathode) active material, reversibly cycling alkali metal ions with a compatible negative electrode (anode) active material. DESCRIPTION OF THE INVENTION [0014] It has been found that the novel electrode materials, electrodes, and batteries of this invention afford benefits over such materials and devices among those known in the art. Such benefits include one or more of increased capacity, enhanced ionic and electrical conductivity, enhanced cycling capability, enhanced reversibility, and reduced costs. Specific benefits and embodiments of the present invention are apparent from the detailed description set forth herein below. It should be understood, however, that the detailed description and specific examples, while indicating embodiments among those preferred, are intended for purposes of illustration only and are not intended to limited the scope of the invention. [0015] The present invention provides electrode active materials for use in an electricity-producing electrochemical cell. Each electrochemical cell includes a positive electrode, a negative electrode, and an electrolyte in ion-transfer communication with both the positive and the negative electrode for transferring ionic charge carriers there between. A "battery" refers to a device having one or more electricity-producing electrochemical cells. Two or more electrochemical cells may be combined, or "stacked," so as to create a multi-cell battery. [0016] The electrode active materials of this invention may be used in the negative electrode, the positive electrode, or both. Preferably, the active materials of this invention are used in the positive electrode. As used herein, the terms "negative electrode" and "positive electrode" refer to the electrodes at which oxidation and reduction occur, respectively, during battery discharge; during charging of the battery, the sites of oxidation and reduction are reversed. Electrode Active Materials: [0017] The present invention provides oligo phosphate-based electrode active materials (herein "electrode active materials"). Such electrode active materials are represented by the general nominal formula (I): A.sub.aM.sub.bX.sub.cO.sub.(3c+1). (I) [0018] The term "nominal formula" refers to the fact that the relative proportion of species (e.g. A, M, X and O) may vary slightly on the order of 2 percent to 5 percent, or more typically, 1 percent to 3 percent. [0019] A of general formula (I) is an alkali metal or a mixture of alkali metals. In one embodiment, A is selected from the group consisting of Li (Lithium), Na (Sodium), K (Potassium), and mixtures thereof. A may be mixture of Li with Na, a mixture of Li with K, or a mixture of Li, Na and K. In another embodiment, A is Na, or a mixture of Na with K. In one preferred embodiment, A is Li. [0020] As used herein, the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components, and mixtures thereof. In addition, the words "preferred" and "preferably" refer to embodiments of the invention that afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention. [0021] A sufficient quantity of alkali metal (A) should be present so as to allow all of the "redox active" elements of M (as defined herein below) to undergo oxidation/reduction. In one embodiment, 0<a.ltoreq.6. In another embodiment, 1.ltoreq.a.ltoreq.5. Unless otherwise specified, a variable described herein algebraically as equal to ("="), less than or equal to (".ltoreq."), or greater than or equal to (".gtoreq.") a number is intended to subsume values or ranges of values about equal or functionally equivalent to said number. [0022] Removal of alkali metal from the electrode active material is accompanied by a change in oxidation state of the redox active elements of M (or where M consist of more than one element, by a change in oxidation state of at least one of those elements). The amount of M that is available for oxidation in the electrode active material determines the amount of alkali metal that may be removed. Such concepts are, in general, well known in the art, e.g., as disclosed in U.S. Pat. No. 4,477,541, Fraioli, issued Oct. 16, 1984; and U.S. Pat. No. 6,136,472, Barker, et al., issued Oct. 24, 2000, both of which are incorporated by reference herein. [0023] Referring again to general formula (I), M includes at least one redox active element. As used herein, the term "redox active element" includes those elements characterized as being capable of undergoing oxidation/reduction to another oxidation state when the electrochemical cell is operating under normal operating conditions. As used herein, the term "normal operating conditions" refers to the intended voltage at which the cell is charged, which, in turn, depends on the materials used to construct the cell. [0024] Redox active elements useful herein include those selected from Groups 4 through 11 of the Periodic Table, as well as select non-transition metals, including, without limitation, Ti (Titanium), V (Vanadium), Cr (Chromium), Mn (Manganese), Fe (Iron), Co (Cobalt), Ni (Nickel), Cu (Copper), Nb (Niobium), Mo (Molybdenum), Ru (Ruthenium), Rh (Rhodium), Pd (Palladium), Os (Osmium), Ir (Iridium), Pt (Platinum), Au (Gold), Si (Silicon), Sn (Tin), Pb (Lead), and mixtures thereof. Preferred are the first row transition series (the 4th Period of the Periodic Table), namely those selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and mixtures thereof. In one embodiment, M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Si, Sn, Pb, and mixtures thereof. Continue reading about Oligo phosphate-based electrode active materials and methods of making same... 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