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
  • H01M4/48—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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G45/00—Compounds of manganese
  • C01G45/12—Complex oxides containing manganese and at least one other metal element
  • C01G45/1221—Manganates or manganites with trivalent manganese, tetravalent manganese or mixtures thereof
  • C01G45/1242—Manganates or manganites with trivalent manganese, tetravalent manganese or mixtures thereof of the type (Mn2O4)-, e.g. LiMn2O4 or Li(MxMn2-x)O4
• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/20—Two-dimensional structures
  • C01P2002/22—Two-dimensional structures layered hydroxide-type, e.g. of the hydrotalcite-type
• • 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
  • C01P2002/54—Solid solutions containing elements as dopants one element only
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/77—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by unit-cell parameters, atom positions or structure diagrams
• • 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
• • 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
  • H01M10/052—Li-accumulators
• • 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 to preparing compounds useful as electrode compositions for lithium-ion batteries .
• Lithium-ion batteries typically feature a pair of electrodes, at least one of which contains lithium in the form of a lithium-transition metal oxide. These batteries offer the advantages of high energy storage capacity and rechargeability . For optimum performance, it is desirable to maximize electrode capacity between cutoff voltages in the range of about 2.5V to about 4.2V vs. lithium metal.
• the invention features a compound having the formula Li y Cr x Mn 2 _ x 0 4+z where y > 2 ,
• the invention also features an electrode composition that includes this compound.
• y is about 2.2.
• the invention features a process for preparing a compound that includes the steps of (a) preparing a solution that includes (i) a chromium source, (ii) a manganese source, (iii) a lithium source, and (iv) an oxygen source, the relative amounts of each of the sources being selected to yield, following step (c) , a compound having the formula
• the gel is heated at a temperature less than about 1000°C, preferably less than about 800°C, and more preferably no greater than about
• the solution preferably is an aqueous solution.
• the gel is preferably formed by treating the solution with ammonium hydroxide .
• the chromium, manganese, lithium, and oxygen sources may be in the form of four separate materials, or in the form of a material that combines two or more of these elements.
• the chromium source preferably is a compound consisting essentially of chromium and at least one additional element selected from the group consisting of oxygen, nitrogen, carbon, and hydrogen.
• An example of such a chromium source is a chromium salt such as chromium nitrate. This material acts as a source of both chromium and oxygen.
• the manganese source preferably is a compound consisting essentially of manganese and at least one additional element selected from the group consisting of oxygen, nitrogen, carbon, and hydrogen.
• a manganese salt such as manganese acetate. Similar to the case of chromium nitrate, this material acts as a source of both manganese and oxygen.
• the lithium source preferably is a compound consisting essentially of lithium and at least one additional element selected from the group consisting of oxygen, nitrogen, carbon, and hydrogen.
• a lithium salt such as lithium hydroxide, a material which acts as a source of both lithium and oxygen.
• the chromium, manganese, lithium, and oxygen sources are selected to yield, following step (c) , a compound having the formula Li y Cr x Mn 2 _ x 0 4+z where y > 2, 0.25 ⁇ x ⁇ 2, and z > 0.
• the chromium, manganese, lithium, and oxygen sources are selected to yield, following step (c) , a compound having the formula Li Cr x Mn 2 _ x 0 4+z where y > 2, 0.5 ⁇ x ⁇ 1.5, and z > 0.
• the chromium, manganese, lithium, and oxygen sources are selected to yield, following step (c) , a compound having the formula Li y Cr x Mn 2 . x 0 4+z where y
• the invention features a lithium ion battery that includes: (a) a first electrode that includes a compound having the formula Li y Cr x Mn 2 _ x 0 4+z where y > 2, 0.25 ⁇ x ⁇ 2, and z > 0 ; (b) a second electrode; and (c) an electrolyte, in which the first electrode has a reversible specific capacity of at least 100 mAh/g in the range 2.5V - 4.2V vs. Li metal when discharged at a rate corresponding to full discharge in 10 hours or less.
• the invention provides compounds useful as electrode compositions (e.g., cathode compositions) for lithium-ion batteries.
• the electrode compositions exhibit good performance, as measured, e.g., by reversible specific capacity in the range 2.5V - 4.2V vs. lithium metal. Lithium-ion batteries incorporating such electrode compositions may be repeatedly cycled without substantial loss of performance.
• the compounds are prepared using a sol-gel process that proceeds under relatively mild conditions (e.g., at temperatures preferably less than about 1000°C) and requires relatively short reaction times (e.g., on the order of 10-24 hours) .
• Compounds in which y is greater than 2 offer the advantage of minimizing the presence of transition metals (i.e., chromium and manganese) in the lithium layers of the layered oxide.
• transition metals i.e., chromium and manganese
• Such transition metals can prevent the free diffusion of intercalated lithium, leading to materials having poor intercalation kinetics and poor performance in lithium batteries .
• Fig. 1 is a series of x-ray diffraction profiles for the materials prepared according to Examples 1-7.
• Fig. 2 is a series of expanded views of the x- ray diffraction profiles in the range from 33 to 40 degrees for the materials prepared according to Examples 1, 3, 5, and 7.
• Fig. 3 is an exploded perspective view of an electrochemical cell used to test various electrode compositions .
• Lithium-chromium-manganese oxides described herein have the general formula Li y Cr x Mn 2 _ x 0 4+z where y >
• oxides are particularly useful as electrode compositions for lithium-ion batteries. They are preferably prepared in a sol-gel process in which chromium, lithium, manganese, and oxygen sources are combined to form a solution (preferably an aqueous solution) , which is then converted to a gel by the addition of a reagent such as ammonium hydroxide (NH 4 0H) . The gel is then heated under an inert atmosphere (e.g., an argon atmosphere) to convert the gel to the desired oxide.
• a reagent such as ammonium hydroxide (NH 4 0H)
• the chromium, lithium, manganese, and oxygen sources may be used as the chromium, lithium, manganese, and oxygen sources as long as they are soluble in the medium used to prepare the gel.
• the chromium, lithium, manganes, and oxygen sources must be water-soluble.
• a single material may serve as a source for more than one of these elements.
• Preferred materials are those in which the elemental constituents (with the exception of chromium, lithium, manganese, and at least some of the oxygen) form volatile by-products during the heating step such that these elemental constituents do not become part of the final oxide product.
• the resulting oxide product therefore, contains only lithium, chromium, manganese, and oxygen as its elemental constituents.
• the oxide product is essentially free of impurities which might otherwise compromise electrode performance.
• suitable materials include nitrogen- containing compounds (which can liberate nitrogen- containing gas during heating) , carbon-containing compounds (which can liberate, e.g., carbon dioxide and/or carbon monoxide during heating) , and hydrogen- containing compounds (which can liberate, e.g., water vapor during heating) .
• nitrogen- containing compounds which can liberate nitrogen- containing gas during heating
• carbon-containing compounds which can liberate, e.g., carbon dioxide and/or carbon monoxide during heating
• hydrogen- containing compounds which can liberate, e.g., water vapor during heating
• Specific examples include nitrates, hydroxides, and esters of organic acids such as acetates, citrates, tartrates, and oxalates .
• the heating temperature and stoichiometric ratios of reactants determine the crystal structure (and associated parameters such as lattice constants and unit cell volume) of the oxide product, as well as whether the product is a single or multi-phase material. In general, temperatures less than 1000°C are preferred, with temperatures in the range 500-700°C being particularly preferred.
• Electrodes were prepared as follows. About 12 wt . % Li y Cr x Mn 2 . x 0 4+z (prepared as described below), 6 wt . %
• Kynar Flex 2801 (a vinylidene fluoride- hexafluoropropylene copolymer commercially available from Atochem) , 10 wt. % EC/PC (ethylene carbonate/propylene carbonate, 50/50 by volume), 1.5 wt . % Super S carbon black (commercially available from MMM Carbon, Belgium), and 70.5 wt . % acetone were thoroughly mixed by stirring in a sealed bottle at 50°C for four hours to form a slurry. The slurry was then spread in a thin layer (about 150 micrometers thick) on a glass plate using a doctor blade spreader.
• each circular electrode was first placed in diethyl ether for about 5 minutes to remove EC/PC and form pores in the electrode that the electrolyte will fill during cell construction. The electrodes were then taken into an argon- filled glove box where the electrochemical cell was constructed.
• FIG. 3 An exploded perspective view of the electrochemical cell is shown in Fig. 3.
• the anode was a lithium foil having a thickness of 125 micrometers; the anode also functioned as a reference electrode.
• the cell featured 2320 coin-cell hardware, equipped with a spacer plate (304 stainless steel) and a disc spring (mild steel) .
• the disc spring was selected so that a pressure of about 15 bar would be applied to each of the cell electrodes when the cell was crimped closed.
• the separator was a Celgard #2502 microporous polypropylene film (Hoechst-Celanese) which had been wetted with a 1M solution of LiPF 6 dissolved in a 30:70 volume mixture of ethylene carbonate and diethyl carbonate (Mitsubishi Chemical) .
• SYNTHESIS Example 1
• LiOH-H 2 0 (FMC Corp., 98%) was dissolved in 70 mis of distilled water. While stirring, the LiOH solution was added dropwise to the transition metal solution over a period of about 5 minutes. The solution was stirred for about 15 minutes. Finally, about 10 mis of NH 4 OH was added dropwise over about 5 minutes to form a gel . The gel was then placed in a "Fisher-Brand" muffle oven set to 170°C to dry and solidify the gel overnight in air. After initial drying, the solidified gel was powdered in a Retsch model Rm-0 automatic grinder for about 10 minutes.
• the powdered gel was then heated to 500°C using a Lindberg tube furnace equipped with stainless steel furnace tubes and sealed end caps. After the gel had been loaded into the furnace tube, but before initiating heating, the end caps were sealed, and the furnace tube thoroughly purged with UHP-grade argon (Canadian Liquid Air) , to remove unwanted air. UHP-grade argon was passed at a rate of about 150 cc/min through fittings in the sealed end caps during the synthesis.
• the heating profile was as follows: from 30°C to 150°C in 20 minutes, followed by a 3 hour soak at 150°C. The sample was then heated to 500°C in 40 minutes, soaked for 10 hours, and cooled to room temperature in about one hour to yield a compound having the formula Li 2 Cr x 25 Mn 2 0 4+z where z > 0.
• a powder x-ray diffraction pattern for the product was collected using a Siemens D5000 diffractometer equipped with a copper target X-ray tube and a diffracted beam monochromator . Data was collected between scattering angles of 10 degrees and 130 degrees. A portion of the x-ray diffraction profile is shown in Fig. 1. An expanded view of the profile in the range from 33 to 40 degrees is shown in Fig. 2.
• the crystal structure was determined based upon the x-ray diffraction data as described in (a) C.J. Howard and R.J. Hill, Australian Atomic Energy
• Lattice constants were determined using least squares refinements to the positions of calculated and measured Bragg peak positions, and were used to calculate unit volume according to the procedure described in standard x-ray diffraction texts, e.g., B.D. Warren, X-Ray Diffraction, Addison-Wesley, Reading, MA (1969) .
• the unit volume refers to the volume of the crystal per formula unit of the material, the formula unit being Li y Cr x Mn 2 _ x 0 4+z .
• the unit cell contains 9 formula units.
• the unit cell contains 3/2 formula units.
• the unit cell For the hex structure, indexed on the hexagonal unit cell, the unit cell contains 3/2 formula units. For the d-hex structure, the unit cell contains 1 formula unit.
• the lattice constants and unit volume for the sample are set forth in Table 1.
• a comparison of the measured and calculated Bragg peak positions is set forth in Table 2.
• the calculated values were obtained assuming a layered structure with space group R-3M.
• Examples 2-7 were prepared following the procedure in Example 1 except that a 2 gram sample of the powdered material was further subjected to a heat treatment in the furnace for 24 hours at the following temperatures: 600°C (Example 2), 700°C (Example 3),
• Example 2 The material prepared in Example 2 had a cub/hex structure.
• Example 3 The material prepared in Example 3 exhibited the "layered LiCo0 2 " structure, which will be designated "hex" here.
• the measured and calculated Bragg peak positions for Example 3 are shown in Table 3. The calculated values were obtained assuming a layered structure with space group R-3M.
• Example 5 The crystal structure of the material prepared in Example 5 was a layered one, but with a small distortion, analogous to that recently found for layered LiMn0 2 by Armstrong and Bruce, Nature 381:499 (1996) .
• the observed and calculated Bragg peak positions for Example 5 are summarized in Table 4. This structure will be designated “d-hex”, short for "distorted hexagonal.”
• the calculated values were obtained assuming a layered structure with space group C 2/M.
• Example 7 The crystal structure of the material prepared in Example 7 was also a layered or "hex" structure, but with substantially different Bragg peak positions compared to Example 3.
• the observed and calculated Bragg peak positions for Example 7 are summarized in Table 5.
• the calculated values were obtained assuming a layered structure with space group R-3M.
• Example 4 The material prepared in Example 4 was a two phase mixture of the materials of Examples 3 and 5.
• the material prepared in Example 6 was a two phase mixture of the materials of Examples 5 and 7.
• Example 8 Several electrochemical cells were constructed according to the procedure described above using, as the cathode, samples prepared according to Example 3. Specifically, four cells were prepared using the material of Example 3 and cycled between voltage limits of 2.5V and 4.2V using currents of (a) 1.5 mA/g ("3- 1"), (b) 3.75 mA/g ("3-2"), and (c) 15mA/g (two cells) ("3-3" and "3-4"). The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6. The data demonstrates that the capacity is maintained as the current is increased. Example 8
• Example 8 was prepared following the procedure set forth in Example 1 except that the relative amounts of reactants (Cr (N0 3 ) 3 -9H 2 0, Mn (CH 3 C00) 2 -4H 2 0, and LiOH-H 2 0) were selected to yield a product having the formula Li 2 Cr 1 0 Mn 1 O 0 4+z where z > 0.
• the crystal structure, lattice constants, and unit cell volume were determined as described in Example 1 and are reported in Table 1. Examples 9-14
• Examples 9-14 were prepared following the procedure in Example 8 except that a 2 gram sample of the powdered material was further subjected to a heat treatment in the furnace for 24 hours at the following temperatures: 600°C (Example 9), 700°C (Example 10),
• Example 14 1100°C
• quartz furnace tubes were used.
• the crystal structure, lattice constants, and unit cell volume for each sample with the exception of Examples 9 and 11) were determined as described in Example 8 and are reported in Table 1.
• Example 15 was prepared following the procedure set forth in Example 1 except that the relative amounts of reactants (Cr (N0 3 ) 3 -9H 2 0, Mn (CH 3 C00) 2 -4H 2 0, and LiOH-H 2 0) were selected to yield a product having the formula Li 2 Cr 15 Mn 05 0 4+2 where z > 0. The crystal structure was determined as described in Example 1 and is reported in
• Examples 16-21 were prepared following the procedure in Example 15 except that a 2 gram sample of the powdered material was further subjected to a heat treatment in the furnace for 24 hours at the following temperatures: 600°C (Example 16), 700°C (Example 17),
• Example 18 800°C (Example 18) , 900°C (Example 19) , 1000°C (Example 20) , and 1100°C (Example 21) .
• quartz furnace tubes were used. The crystal structure, lattice constants, and unit cell volume for each sample (with the exception of Example 18) were determined as described in Example 1 and are reported in Table 1.
• Example 22 An electrochemical cell was constructed as described above using the material of Example 17, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA/g. The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6.
• Example 22 An electrochemical cell was constructed as described above using the material of Example 17, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA/g. The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6.
• Example 22 An electrochemical cell was constructed as described above using the material of Example 17, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA/g. The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6.
• Example 22 An electrochemical cell was constructed as described above using the material of Example 17, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA
• Example 22 was prepared following the procedure set forth in Example 1 except that the relative amounts of reactants (Cr (N0 3 ) 3 -9H 2 0, Mn (CH 3 COO) 2 -4H 2 0, and LiOH-H 2 0) were selected to yield a product having the formula
• Example 23 Li 2.2 Cr 1-25 n 0 _ 7S O 4+z where z > 0.
• the crystal structure, lattice constants, and unit cell volume were determined as described in Example 1 and is reported in Table 1.
• Example 23 was prepared following the procedure set forth in Example 22 except that a 2 gram sample of the powdered material was further subjected to a heat treatment in the furnace for 24 hours at 700°C. The crystal structure, lattice constants, and unit cell volume for the sample were determined as described in Example 1 and are reported in Table 1.
• Example 24 An electrochemical cell was constructed as described above using the material of Example 23, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA/g. The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6.
• Example 24 An electrochemical cell was constructed as described above using the material of Example 23, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA/g. The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6.
• Example 24 An electrochemical cell was constructed as described above using the material of Example 23, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA/g. The first charge capacity, first discharge capacity, and time taken to deliver 148 mAh/g were determined and the results reported in Table 6.
• Example 24 An electrochemical cell was constructed as described above using the material of Example 23, and cycled between voltage limits of 2.5V and 4.2V using a current of 15mA
• Example 24 was prepared following the procedure set forth in Example 1 except that the relative amounts of reactants (Cr (N0 3 ) 3 -9H 2 0, Mn (CH 3 COO) 2 -4H 2 0, and Li0H-H 2 0) were selected to yield a product having the formula Li 2 Cr 0 _ 5 Mn-_ s O 4+z where z > 0, and the firing temperature was 300°C. The crystal structure, lattice constants, and unit cell volume were not determined. Examples 25-30
• Examples 25-30 were prepared following the procedure in Example 24 except that a 2 gram sample of the powdered material was further subjected to a heat treatment in the furnace for 24 hours at the following temperatures: 600°C (Example 25), 700°C (Example 26),
• Example 31 was prepared following the procedure set forth in Example 1 except that the relative amounts of reactants (Cr (N0 3 ) 3 -9H 2 0, Mn (CH 3 C00) 2 -4H 2 0, and LiOH-H 2 0) were selected to yield a product having the formula Li 2 Cr 075 Mn x 25 0 4+z where z > 0. The crystal structure, lattice constants, and unit cell volume for the sample were determined as described in Example 1 and are reported in Table 1. Examples 32-37
• Examples 32-37 were prepared following the procedure in Example 32 except that a 2 gram sample of the powdered material was further subjected to a heat treatment in the furnace for 24 hours at the following temperatures: 600°C (Example 32), 700°C (Example 33), 800°C (Example 34), 900°C (Example 35), 1000°C (Example 32), 700°C (Example 33), 800°C (Example 34), 900°C (Example 35), 1000°C (Example
• Example 36 Example 36
• Example 37 1100°C
• quartz furnace tubes were used.
• the crystal structure, lattice constants, and unit cell volume of Example 36 were determined as described in Example 31 and are reported in Table 1.
• the crystal structure, lattice constants, and unit cell volume for the remaining examples were not determined.

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