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
  • H01M4/58—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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/003—Titanates
  • C01G23/005—Alkali titanates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G25/00—Compounds of zirconium
• • 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
• • 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
  • H01M4/04—Processes of manufacture in general
• • 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
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
• • 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/50—Solid solutions
  • C01P2002/52—Solid solutions containing elements as dopants
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
• • 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 relates generally to alkali metal titanates, and more particularly to lithium titanates. More specifically, the invention relates to doped lithium titanates and to a method for manufacturing lithium titanate materials which exhibit superior electrochemical properties when incorporated into lithium batteries.
• Alkali metal titanates have electrochemical properties which make them desirable as electrode materials for a variety of devices.
• Lithium titanate Li 4 TIsO 12
• It is a relatively low-cost material, and exhibits high performance characteristics in lithium batteries; consequently, it is anticipated to have significant utility as an electrode material for high performance, high power batteries such as those utilized in hybrid electric vehicles and other high power applications.
• rate capacity One important characteristic of high power, high performance batteries is rate capacity. That is, the rate at which the batteries can take up and deliver an electrical charge. This parameter is particularly important under high charge/ discharge rates as are encountered in electric vehicles and other high power applications.
• First cycle reversibility is another very important parameter for rechargeable lithium batteries. This parameter measures the decline in storage capacity when a freshly manufactured lithium battery is initially cycled. Manufacturers compensate for this initial loss by building extra capacity into batteries. However, this approach increases the size and cost of batteries, and industry has always sought to limit magnitude of first cycle reversibility.
• Various lithium titanate materials are commercially available and are utilized in the manufacture of lithium batteries. However, heretofore available commercial materials produce lithium batteries having first cycle reversibilities of approximately 80%, which represents a significant inefficiency. Furthermore, there is a need to improve the rate capacities of prior art batteries to make them practical for use in high power applications. Clearly, there is a need for improved lithium titanate electrode materials.
• the dopant may comprise a transition metal, and this metal may be one or more of V, Zr, Nb, Mo, Mn, Fe, Cu, and Co.
• the dopant may be present in amounts up to 20 atomic percent, and in specific instances in the range of 0.1-5 atomic percent.
• the dopant comprises Zr.
• alkali metal titanates such as doped and/or undoped lithium titanate.
• the method involves preparing a mixture of an alkali metal compound such as lithium carbonate together with a titanium compound such as titanium dioxide or some other oxide of titanium, including suboxides. This mixture is impact milled by ball milling, attritor milling or the like, and the resultant mixture is heated for a time and at a temperature sufficient to bring about a reaction which forms the alkali metal titanate.
• a dopant material or dopant precursor may be added to the mixture before or after the milling step.
• electrodes which include alkali metal titanates in accord with the foregoing, as well as batteries in which these electrodes comprise the anodes. BRIEF DESCRIPTION OF THE DRAWINGS
• Figure 1 is a flowchart illustrating a process for synthesizing alkali metal titan ates
• Figure 2 is a time versus temperature plot illustrating a temperature programmed reaction schedule which may be utilized to fabricate the titanate materials
• Figure 3 is another time versus temperature plot illustrating another temperature programmed reaction which may be utilized to fabricate the materials;
• Figure 4 is a graph showing tile capacity retention of a cell which incorporates a lithium titanate anode;
• Figure 5 is a graph showing the cycle life of the cell of Figure 4.
• Figure 6 is a graph illustrating the first cycle capacity loss of a prior art cell and a cell which incorporates the present lithium titanate material.
• lithium titanate is recognized as having the formula Li 4 TIsOi 2 ; however, as is recognized in the art, the stoichiometry of this material may, in some instances, vary without significantly altering the fundamental nature of the material. Such variations may be resultant from a slight oxidation or reduction of the material, minor variations of the LiTi ratio and the presence of dopant species. Accordingly, within the context of this disclosure, all of such stoichiometric and non-stoichiometric materials are encompassed within the definition of lithium titanate.
• the lithium titanate is doped with a transition metal in an amount up to approximately 20 atomic percent, and some such transition metals include one or more of V, Zr, Nb, Mo, Mn, Fe, Cu, and Co.
• the dopant comprises Zr, and in particular instances is present in an amount of 0.1-5 atomic percent of the material.
• the doped materials provide for cells which manifest a high charge capacity under high charge and discharge rates. These improvements are greatest at very high (10-20C) rates, and as a result, cells made utilizing the doped lithium titanate material have particular advantages for use in high rate, high power applications such as electric vehicles and backup power systems. Results similar to the foregoing are anticipated utilizing other transition metals as dopant agents. Dopant concentrations generally range up to 20 atomic percent of the material.
• lithium titanate is prepared from a mixture Of Li 2 CO 3 and TiO 2 with a molar ratio of 2:5 at step 10. These precursor materials are mixed together in a solvent at step 20, such as isopropanol. Other solvents, including organic liquids, aqueous liquids and the like may be utilized to the extent they do not interfere with the process.
• the mixture is then subjected to a ball milling process at step 30.
• a typical milling process is carried out in ceramic jars utilizing zirconia milling media for approximately 48 hours, although milling times can typically range from 10 minutes to 240 hours. In a specific instance, milling takes place for at least 12 hours.
• step 30 illustrates a ball milling process
• any impact milling process such as attritor milling, vibratory milling and the like, may be employed.
• the precursor mixture is dried to remove the solvent at step 40, and ground in air to produce a fine powder at step 50.
• the mixed precursors are then subjected to a temperature programmed reaction (TPR) under air or oxygen, or an inert gas, in a furnace at step 60.
• TPR temperature programmed reaction
• the material is typically heated to a temperature of no more than 1000 0 C.
• the material is taken from room temperature to a temperature of 400 D C over a period of 0.5 hour; held at 400 0 C for 2.5 hours; raised to SOO 0 C over a period of 3 hours; maintained at 800°C for 12 hours and then cooled to room temperature as illustrated by the time versus temperature graph shown in Figure 2.
• the material is taken from room temperature to a temperature of 800 0 C over a period of an hour, held at 800 0 C for two hours, then cooled to room temperature as shown in Figure 3.
• doped lithium titanate is prepared from starting materials which include Li 2 CO 3 and TiO 2 , together with a dopant precursor compound, which for purposes of illustration will be a zirconium dopant.
• the precursor may comprise a carbonate, acetate, chloride, alkoxide, or other compound of the dopant metal.
• the molar ratio of Li:(Ti+Zr) is 4:5 with the concentration of Zr being 0.1-5 mole percent of Ti+Zr.
• the precursors are mixed in an appropriate solvent, milled, and further processed as described above to produce the doped material.
• titanate materials both doped and und ⁇ ped, produced by the foregoing method in which precursor materials are milled together, provide titanate products having superior properties which are manifest in cells in which they are incorporated.
• the methods and materials of the present invention are distinguished from those of the prior art, which prior art is acknowledged to include the use of impact milling steps implemented on the titanate material after it has been synthesized.
• Table 2 summarizes some physical parameters measured for prior art lithium titanate materials, referred to in the table as prior art LTO, and materials made in accord with the foregoing, referred to in the table as T/J LTO.
• material made in accord with the present procedure has a particle size greater than that of the prior art material.
• the surface area of the materials of present invention is correspondingly smaller, which implies that the materials of present invention can be more stable or safer than the prior art material, in an electrochemical environment.
• Ionic conductivity of the material of present invention is higher than that of the prior art material by approximately an order of magnitude.
• the first cycle reversibility of cells which incorporate the material of the present invention is approximately 95%, while that of the prior art is only 80%.
• FIG. 4 shows the rate capability of cells prepared utilizing the present lithium titanate materials, As will be seen, the cell of Figure 4 shows an excellent rate capability with 98% capacity retention at a 2OC discharge rate, and 91% capacity retention at a 50C rate. Cells of this type have excellent utility in high power, high performance applications.
• Figure 5 shows the cycle life of a cell of the type illustrated with reference to Figure 4 and depicts discharge capacity retention as a function of charge/discharge cycles carried out at 3C/-3C. As will be seen, this cell retains over 90% of its capacity after 6000 cycles.
• the materials of the present invention have properties which allow for the fabrication of lithium batteries which are stable, efficient, and capable of reliably delivering very high levels of power. These properties, together with the low costs achieved through the use of the disclosed methods, make this technology particularly advantageous for the manufacture of high power battery systems such as those used in electric vehicles, large power tools, power backup systems, and the like.

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• 2007
  • 2007-06-04 US US11/757,658 patent/US7879493B2/en active Active
  • 2007-06-05 CA CA002654605A patent/CA2654605A1/en not_active Abandoned
  • 2007-06-05 KR KR1020087031175A patent/KR101410844B1/ko active Active
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