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  • 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
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  • 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
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  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
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  • 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
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  • 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
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  • C01P2002/30—Three-dimensional structures
  • C01P2002/32—Three-dimensional structures spinel-type (AB2O4)
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  • 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
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  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
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  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
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  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • 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

• Lithium-ion batteries continue to dominate the rechargeable battery market. Found in nearly every type of handheld rechargeable phone, music player and many other devices, secondary batteries relying upon lithium metal oxides as the cathode composition eventually experience fade and loss of capacity. Capacity loss increases over the life of the battery necessitating recharging of the battery more frequently.
• electrolytes such as LiPF 6 react with water to form HF according to the following equation:
• cathode materials utilizing first row transition metals such as Co, Mn, Ni, Fe and V (possibly doped with other elements) are equally susceptible to degradation by FIF, Accordingly, the ability to shield the cathode material from HF attack without detrimentally reducing battery performance will be commercially advantageous,
• the present invention provides a cathode composition.
• the cathode composition includes a lithium metal oxide suitable for use in lithium ion batteries.
• the lithium metal oxide carries a lithium fluoride surface treatment sufficient to substantially preclude degradation of the lithium metal oxide by acids.
• the present invention provides a cathode composition prepared from a lithium metal oxide (LMO) spinel material having the general formula of Lii +x M y Mn 2-x- y04 where 0 ⁇ x ⁇ 0.25, 0 ⁇ y ⁇ 0.5 and M is one or more trivalent metals from the group Al, Cr, Ga, In and Sc.
• the cathode composition is prepared from a layered material Li[Li ( i-2 X ) 3MyMn ( 2- x y3Ni x-y ]0 2 where 0 ⁇ x ⁇ 0.5, 0 ⁇ y ⁇ 0.25, x>y and M is one or more metals chosen from Ca, Cu, Mg and Zn.
• LMO lithium metal oxide
• the cathode active material both materials carry a lithium fluoride surface treatment sufficient to substantially preclude degradation of the lithium metal oxide by acids.
• the resulting cathode active material has improved fade over multiple cycles while maintaining the desired capacity.
• the present invention provides a method for preparing cathode material.
• the method includes the steps of dry blending lithium metal oxide with lithium fluoride (LiF) particles followed by heating the resulting dry blend at a temperature and for a period of time sufficient to activate the LiF as a surface treatment on the lithium metal oxide, i.e. the LiF is carried by the lithium metal oxide in a manner to provide the desired protection,
• the present invention provides a method for preparing a cathode material suitable for use in a lithium ion battery.
• the method includes the steps of dry blending a cathode active material having the general formula of Li 1+x M y Mn 2-x-y 0 4 where 0 ⁇ x ⁇ 0.25, 0 ⁇ y ⁇ 0.5 and M is one or more trivalent metals from the group Al, Cr.
• LiF lithium fluoride
• the dry blending step utilizes a sufficient amount of LiF such that the resulting blend has from about 0.25 to about 2.5% by weight LiF.
• the dry blending step occurs at a temperature between about 10°C and 30°C.
• the resulting dry blend material is heated to a temperature between about 700°C to about 850°C to provide a final composition in the form of a cathode active material carrying a surface treatment of LiF.
• Using the resulting cathode active material provides a cathode having a capacity of at least and more preferably greater than lOOmAh g (milliAmpHour/gram) after 200 cycles.
• the present invention provides an alternative method for preparing lithium manganese oxide compounds suitable for use as cathode material.
• This method includes the steps of: ⁇ selecting a cathode active material having the general formula of Lii +x M y Mn 2-x . y0 4 where 0 ⁇ x ⁇ 0.25, 0 ⁇ y ⁇ 0.5 and M is one or more trivalent metals from the group Ai, Cr, Ga, In and Sc or Li[Li ( i. 2x)/3 M y Mn(2- x )/3Ni x-y ]0 2 where 0 ⁇ x ⁇ 0.5, 0 ⁇ y ⁇ 0.25, x>y and M is one or more metals chosen from Ca, Cu, Mg and Zn;
• Figure la is an X-Ray Diffraction scan of LiMn 2 04 without a surface treatment of lithium fluoride.
• Figure lb is an X-Ray Diffraction scan of LiMn 2 0 4 carrying a surface treatment of lithium fluoride.
• Figure 2 is a graph of the cycling capacity at 60°C comparing Lii i o6Cro. 1 Mni.s 4 0 4 carrying a surface treatment of LiF heat treated in a rotary calciner at 850°C with a residence time of 4 - 5 hours (Line C) to untreated Lii.06Cro.1Mn1.s4O4 (Line A) and to Li 1 .o6Cro, 1 Mn 1 ,840 4 , lacking LiF, but heat treated in a rotary calciner at 850°C with a residence time of 4 - 5 hours (Line B).
• FIG. 3 is a graph of the cycling capacity at 60°C comparing Li1.06Alo.i8 n1.76O4 carrying a surface treatment of LiF heat treated twice in a box oven at 850°C (Line F) to untreated Li 1 .06Alo. i8Mn1.76O4 (Line D) and to Li1.00Alo.i8Mn1.76O4 carrying LiF but not heat treated (Line E).
• FIG. 4 is a graph of the cycling capacity at 60°C comparing Li 1 .06Alo.i 8 n1.76O4 carrying a surface treatment of LiF heat treated in a box oven at 850°C (Line H) to untreated Li1.06Alo . i8Mni.75O4 (Line D) and to Li1 . 06AlojgMn1.76O4 lacking LiF but heat treated in a box oven at 850°C (Line G). Each data point represents the discharge of the cathode to an indicated 3 volts over 60 minutes followed by recharging to an indicated 4.3 volts over 180 minutes.
• Figure 5 is a graph of the cycling capacity at 60°C comparing untreated Lii,o f iAIo.i8Mni , 7 6 04 (Line D) to Li1.06Alo. i8Mn1.76O4 free of LiF but heat treated in a box oven at 850°C (Line G), to Lij . oeAlo . isMni 76 04 free of LiF but heat treated twice in a box oven at 850°C (Line J), to Lii.o6Alo.i 8 Mni.
• Figure 6 is a graph demonstrating the ability to reduce the concentration of doping metal (Cr) while retaining the original cathode active material structure and improving cathode material capacity by treating with LiF and heat treating the material. Each data point represents the discharge of the cathode to an indicated 3 volts over 60 minutes followed by recharging to an indicated 4.3 volts over 180 minutes.
• Cr doping metal
• the present invention provides a lithium metal oxide composition particularly suited for use as cathode material in a lithium ion battery.
• the particles of lithium metal oxide (LMO) carry a surface treatment of lithium fluoride.
• the lithium fluoride is not a battery active material, the presence of the LiF on the surface of the LMO particle is believed to shield the metal component from acidic digestion. Since the LiF does not contribute to capacity, the preferred embodiment will use only that amount necessary to protect the LMO from acidic digestion without detrimentally impacting capacity,
• the surface treatment of LiF will not completely encapsulate the LMO particle. Rather, without intending to be limited by theory, we believe the LiF isolates a sufficient portion of the exposed manganese sites on the surface of LMO from the electrolyte thereby limiting the oxidation reaction known to degrade the LMO without interfering with the electrolytic reaction. Expressed on a percent by weight basis, the LiF component of the final LMO particle is between about 0.25% to about 2.0% by weight of the LMO/LiF particle inclusive of LMO material containing a doping metal.
• the addition of doping metals to LMO stabilizes the cathode active structure during charge/discharge cycles by replacing a portion of the manganese ions within the cathode active material structure.
• the addition of the doping metal does not generally change the LMO particle size.
• the doping metal does not normally contribute to the capacity of the cathode material under typical lithium ion battery operational conditions.
• LMO can have from about 0.1% to about 15% doping metal by weight. More typically, LMO will have from about 0.5% to about 5% doping metal by weight. Therefore, reducing the concentration of doping metal will enhance battery capacity and reduce manufacturing costs.
• LMO suitable for use as the base particle includes, but is not necessarily limited to, spinel material having the general formula of:
• M is one or more trivalent metals from the group Al, Cr, Ga, In and Sc or a layered LMO having the general formula of: Li[Li ( i -2x )/3M y Mn ⁇ 2-x)/3 Ni x . y ] 0 2
• M is one or more metals chosen from Ca, Cu, Mg and Zn,
• particles sizes refer to median particle size as determined by laser granulometry.
• the LMO with or without doping metal will have particle sizes of about 10 microns or less. More commonly, prior to blending with LiF the LMO, with or without doping metal, will have particle sizes ranging from 3 to about 10 microns.
• the LMO particle with a surface treatment of LiF has a cubic crystalline structure, Thus, neither the surface treatment of LiF nor the method of adding a surface treatment of LiF to the cathode active material alters the crystalline structure of the LMO. Further, the surface treatment of LiF does not form a "layered" LMO as that term is used by those skilled in the art. As reflected in FIG.
• the LMO carrying a surface treatment has x- ray diffraction peaks identified by letters P, S and T at 38.6°, 44.84° and 65.46° 2 ⁇ respectively, (Cu Ka radiation) whereas x-ray diffraction scan of FIG. la of the untreated LMO does not have the corresponding peaks.
• Preferred LMO cathode active material compositions suitable for carrying the LiF surface treatment include: Lu.06Alo.1 gMn1.76O4; Li1.06Mn1.94O4; Li 1 .06Cro.1Mn1.g4O4; Li1.05Alo.12Mn1.8sO ; Lii 07Mni.9 3 O4 and LiNio.5Mn1.5O4.
• each compound may be doped with a metal selected from the following group: Mg, Al, Cr, Fe, Ni, Co, Ga, In, Sc, In, Cu or Zn. Use of a doping metal helps to stabilize the structure of the cathode active material during discharge/recharge cycles.
• the doping metal is generally not a battery active material. Therefore, use of doping metal reduces the overall capacity per gram of the cathode material. Incorporation of the LiF surface treatment will reduce the requirements for doping metal thereby improving capacity of the final cathode material. In general, a cathode material having a LiF surface treatment will require about 50% less doping material than a cathode material lacking LiF surface treatment. Commonly, cathode materials with the LiF surface treatment will have from about 0.5 % to about 2.0 % by weight doping material. Typically, the cathode material will have a capacity of 105 mAH/g to 120 mAH/g.
• the LMO with surface treatment of LiF is particularly suited for use as a cathode material in lithium ion batteries.
• Preparation of the LMO carrying a surface treatment of LiF may use one of two new methods. Both methods advantageously utilize a neutral salt, thereby eliminating handling problems associated with hydrofluoric acid.
• the preferred method dry blends the components followed by heating to activate the LiF surface treatment. Both methods are discussed in detail below. Methods for preparing the base LMO are well known to those skilled in the art and will not be discussed herein.
• a dry powdered LMO having particle sizes between about 3 microns to about 10 microns is blended with lithium fluoride having particle sizes between about 1 micron to about 5 microns.
• the amount of LiF added to the dry LMO powder may range from about 0.25% to about 2.5% by weight of the LMO powder initially charged to the blending unit.
• the type of blending unit is not critical to the current method. Suitable blending units include, but are not limited to, ball mills, vibratory mills, and Scott mills as well as any other convenient dry powder blending mill. Blending typically continues for a period sufficient to achieve a homogenous blend. Although some blending may occur during the heating process, preferably the powders are homogenously blended prior to the following heating step.
• typical blending times may range from about 15 minutes to about two hours with the total time dependent upon the quantity of materials and blending conditions.
• One skilled in the art will be able to readily adjust the blending conditions to achieve the desired homogenous blend of dry materials.
• the dry powder is heated. If so equipped, heating may occur within the mixing unit; however, typically the dry powder will be transferred to a rotary calciner. Within the rotary calciner, heating occurs with continued mixing of the powder. In general, the mixing occurring during heating precludes agglomeration and helps maintain even distribution of the particles.
• the dry powder is heated to a temperature sufficient to adhere the LiF to the surface of the LMO. Typically, the heating step takes place at a temperature sufficient to soften the LiF. As noted above, LiF is not a battery active material. Thus, the addition of too much LiF to the LMO will have a detrimental effect on the resulting cathode material.
• the heating range approximates the melting point of LiF under the operating conditions. Accordingly, heating generally occurs between 840°C and 855 D C. More commonly, heating occurs at about 850°C.
• the heating step takes place over a period of about two to five hours.
• the heating step is controlled to limit the deposition of LiF on the surface of the LMO and preclude loss of lithium from the cathode active material structure during the heating step.
• the heating step is limited to ensure the production of LMO with a surface treatment of LiF having maximum capacity with maximum protection against acid degradation.
• heating may vary with operational conditions such as humidity, moisture content of the blended powder, as well as the mass of powder. In general, heating the blended powder will preferably take place over a period of about two to about four hours.
• the heating step is believed to fuse the LiF to the LMO.
• the resulting surface treatment of LiF provides a sufficient barrier to protect the LMO from acid degradation (i.e. acid attack) without substantially inhibiting necessary ion transport.
• the presence of the LiF on the surface of the LMO precludes reaction of HF or F " with the LMO thereby precluding loss of the manganese component of the LMO.
• the LiF isolates a sufficient portion of the exposed manganese sites on the surface of LMO from the electrolyte thereby limiting the oxidation reaction known to degrade the LMO without interfering with the electrolytic reaction. Accordingly, a cathode prepared from the resulting LMO with surface treatment of LiF has reduced fade over a plurality of cycles while retaining substantially all the initial capacity of the LMO lacking the LiF surface treatment.
• the LMO with surface treatment of LiF may be prepared by a solution process.
• a slurry of LiF is prepared in water and heated to a temperature between about 40°C and 60°C.
• the final slurry has from about 0.1% to about 1.0% LiF by weight.
• the method then blends LMO into the slurry. Stirring of the blended slurry continues until the slurry is a homogenous dispersion of LiF and LMO.
• the solids are separated from the slurry by drying or other convenient method and subsequently heated ' to a temperature between about 600°C and 850°C. The heating step continues for a period sufficient to provide a surface treatment of LiF on the LMO.
• Both methods for preparing the treated LMO will commonly include the further step of sifting or sieving the final product to isolate particles having the desired size.
• Final particle sizes may range from 3 ⁇ to about 30 ⁇ .
• final particles ranging from about 3 ⁇ to about 10 ⁇ are desired for formation of cathodes used in lithium ion batteries.
• the present invention also provides an improved cathode material utilizing the LMO with surface treatment of LiF discussed above.
• Cathode material utilizing the LMO/LiF composition will have improved fade characteristics and an initial capacity comparable to the same LMO lacking the surface treatment of LiF. As reflected by FIGS. 2-5, the LMO/LiF composition actually provides both improved fade characteristics and improved capacity.
• cathodes prepared from LMO carrying surface treatment of LiF had significantly better capacity after 250 discharge/charge cycles thereby reflecting improved fade characteristics. Additionally, each sample of LMO/LiF had an initial capacity within 10% of the untreated LMO.
• the LiF treated LMO was used to produce the cathodes incorporated into coin cell batteries for the purposes of determining capacity and fade rate of the cathodes.
• the LMO treated with LiF carried 1% by weight LiF.
• each indicated heat treatment occurred at 850°C for a period of 120 minutes in a box oven. (Note: although described in connection with a box oven, any conventional heating device suitable for heating the LMO carrying LiF for a period sufficient to activate the LiF will suffice.)
• Each sample, with or without a surface treatment of LiF was prepared using the dry blending method described above.
• the FIGS reflect the initial capacity of the active cathode material, i.e.
• FIG. 2 depicts capacity testing results for cathodes prepared from untreated LMO (line A), LMO lacking LiF but heat treated once at 850°C as described below in Example 6 (line B) and LMO carrying the LiF treatment and heat treated at 850°C as described below in Example 7 (line C).
• line D reflects the capacity for a cathode prepared from LMO free of LiF.
• Line E reflects the capacity of a cathode prepared using LiF treated LMO but not heat treated.
• Line F reflects the capacity of a cathode prepared from LiF/LMO heat treated twice at 850°C.
• line D corresponds to line D of FIG. 3.
• Line G reflects the capacity of a cathode prepared from LMO free of LiF with a single heat treatment at 850°C.
• Line H reflects the capacity of cathode prepared from a LiF treated LMO heat treated once at 850°C,
• line D corresponds to Line D in FIGS. 3 and 4
• line F corresponds to line F in FIG. 3.
• Lines G and H correspond to lines G and H in FIG. 4.
• Line J reflects the capacity of a cathode prepared from LMO free of LiF but heat treated twice at 850°C. As reflected in FIG. 5, Line J has greater initial capacity than Lines F and H; however, Line J has a greater fade rate than Lines F and H. Although not wishing to be bound by theory, we believe that the double heat treatment of the LMO reduced the number of defects in the LMO leading to increased capacity. With reference to FIG. 6, Line K represents an LMO doped with 1.4 weight % Cr, but lacking LiF thereby providing a final LMO with the formula of (Li1 . 05Cro.05Mni.9O4).
• the line K material had an initial capacity of 118.2 mAh/g and a capacity of 78.0 mAh/g after 300 cycles.
• Line L represents an LMO doped with twice as much Cr (2.9 weight %), but lacking LiF thereby providing a final LMO with the formula of (Li1.05Cro . 1Mn1.85O4).
• the line L LMO had an initial capacity of 115.9 mAh/g and a capacity of 83.2 mAh/g after 300 cycles.
• Line M represents LMO with only 1.4 weight% Cr; however, the Line M LMO was treated with LiF and heat treated at 850°C.
• the Line M LMO is represented by (Li1 . 05Cro.05Mn1 . 9O4).
• the Line M material had an initial capacity of 1 18.2 mAh/g and a capacity of 99.5 mAh/g after 300 cycles. As reflected in FIG. 6, the LiF treatment is even more effective at stabilizing the capacity of the LMO than additional dopant in the structure. Table 1 provides the individual cycle values in mAh/g for each sample depicted in FIGS. 2-5.
• the LMO treated with LiF and heat treated at 850°C as described in Example 7 had an initial capacity of 1 12.9 mAh/g
• the line C sample had a final capacity value of 104.9 mAh g.
• the untreated LMO (line A) had an initial capacity 114, 1 mAh/g.
• the line A sample had a capacity value of 95.6 mAh/g.
• LMO free of LiF but heat treated once at 850°C as described in Example 6 (line B) had an initial capacity of 116.4 mAh/g and a capacity of 99.4 mAh g following 246 cycles.
• LMO treated with LiF and heat treated once at 850°C had an initial capacity of 110.7 mAh/g and a capacity of 104.5 mAh/g after 250 cycles.
• the sample represented by line H had a capacity of 103.9 mAh/g after 300 cycles.
• LMO treated with LiF and heat treated twice at 850°C had an initial capacity of 106.1 mAh g and a capacity of 102.0 mAh/g after 300 cycles.
• Line D reflecting untreated LMO, indicates an initial capacity of 108.0 mAh/g and a capacity of 93.1 mAh/g after 250 cycles.
• Line E reflecting LMO treated with LiF but not heat treated, indicates an initial capacity of 106.2 mAh/g, a capacity of 91 ,7 mAh/g following 250 cycles and a capacity of 89.8 mAh g following 300 cycles.
• Line G reflecting LMO lacking LiF but heat treated once at 850°C, indicates an initial capacity of 111.4 mAh/g, a capacity of 103.9 mAh/g following 250 cycles and a capacity of 102.6 mAh/g following 300 cycles.
• Line J reflecting LMO lacking LiF but heat treated twice at 850°C, indicates an initial capacity of 113.9 mAh/g, a capacity of 104.3 mAh/g following 250 cycles and a capacity of 102.9 mAh/g following 300 cycles.
• Each Line in Figures 2-6 represents capacity values for the cathode material used in the coin cell batteries prepared as described in the following examples. The coin cell batteries were cycled at 1C discharge rate and C/3 charge rate at 60°C.
• Example 1 A spinel material with a nominal composition of Lii .0 6Al 0 . i8Mni . 7 6O 4 was prepared as follows. 216. Og of Mn 2 0 3 , 59.62g of Li 2 C0 3 and 14.036g of A1 2 0 3 were mixed together and the mixture was then ball milled for 2 hours (enough to thoroughly mix the materials but not decrease particle size). This mixture was then heated in a ceramic dish in a box furnace at 850°C for 10 hours. (This ten-hour heat treatment forms the initial LMO material.
• LiF surface treatment generally includes an additional heat treatment step.
• the temperature was decreased from 850°C to room temperature at a rate of 2 D C/min.
• the resulting conventional LMO product was then passed through a -325 mesh screen.
• Example 2 A lithium coin cell battery was made with a cathode disk containing 30 percent by weight of carbon black as a conductivity aid, 5 percent by weight of polyvinylidene fluoride (PVDF) as a binder and 65 percent by weight of the cathode active material from Example 1, a Li foil anode and an electrolyte comprised of 1M LiPF6 dissolved in a mixture of equal parts by weight of ethylene carbonate and dimethylcarbonate.
• PVDF polyvinylidene fluoride
• Line D in Figure 3 represent the capacity values of the cathode material prepared from the conventional non-heat treated LMO material prepared in Example 1 and incorporated into the cathode of a coin cell battery prepared in Example 2,
• Example 3 To demonstrate the effect of an additional heat treatment on conventional LMO, about 50g of Li1.05Alo. t8Mni.76O4 from Example 1 was heated in a ceramic dish in a box furnace at 850°C for 2 hours. The temperature was decreased from 850°C to room temperature at a rate of 2°C/min. This material was passed through a -325 mesh screen and then tested in a lithium coin cell battery as prepared in Example 2, Line G in Figure 4 represents the capacity values for a cathode material prepared from the heat treated conventional LMO.
• Example 4 To demonstrate the effect of LiF treatment in conjunction with two heat treatment steps, 201.4 g of Lii.06Alo.1sM i.7gO4 from Example 1 was mixed with 2.0 g of LiF (1% by weight) and ball milled for 2 hours. 20g of this mixture was heated at 850°C for 2 hours in a ceramic crucible placed in a box furnace. Once cooled, the powder was hand mixed with a mortar and pestle to ensure homogeneity and reheated again at 850°C for an additional 2 hours. The temperature of the box furnace was decreased to room temperature at a rate of 2°C/min. This material was passed through a -325 mesh screen and then tested in a lithium coin cell battery as prepared in Example 2.
• Line F in Figure 3 represents the capacity values of cathode material prepared from the LiF treated LMO.
• FIG. 3 clearly demonstrates the improvement provided to the coin cell by using a cathode incorporating LMO having a surface treatment of LiF and prepared using two heat treatments over the heat treated conventional LMO and the non- heat treated conventional LMO.
• Example 5 A conventional LMO was prepared using a spinel material with a nominal composition of was prepared as follows. 37.784kg of Mn 2 0 3 , 2.017kg Cr 2 0 3 and 10.185kg of Li 2 C0 3 were placed in a vibratory mill and mixed with ceramic media for 45 minutes. This step was repeated until about 700kg of spinel premix was obtained. The premix was then reacted in a rotary calciner with temperature settings of 850°C in all heating zones. An oxygen rich atmosphere was flowing through the calciner during the first pass through. Subsequent passes were achieved with normal air flow through the calciner. The material was repeatedly passed through the calciner until a total residence time of 10 hours at 850°C was attained.
• Line A in Figure 2 represents the capacity values for cathode material prepared from the non-heat treated, LiF free LMO.
• Example 6 To demonstrate the effect of a heat treatment on the LMO of Example 5, approximately 25kg of Li 1 .06Cro . 1Mnj.84O4 prepared in Example 5 was passed through a rotary calciner at 850°C at a rate sufficient to achieve a 4-5 hour residence time. The material was then passed through a rotary calciner a second time with the temperatures in the heating zones decreasing to achieve about a slow cool rate of about 1.5°C7min down to 600°C. The cooled product was passed through a -325 mesh screen and then tested in a lithium coin cell battery as prepared in Example 2. Line B in Figure 2 represents the capacity values for a cathode material prepared from the heat treated conventional LMO.
• Example 7 To demonstrate the effect of LiF treatment and a single heat treatment step, 4.4kg of Li
• FIG. 2 clearly demonstrates the improvement provided to the coin cell by using a cathode incorporating the LMO carrying a surface treatment of LiF prepared using a single heat treatment step over the heat treated conventional LMO and the non-heat treated conventional LMO.
• FIGS. 2-6 demonstrate that the utilization of a cathode prepared from LMO having a surface treatment of LiF provides an improved secondary battery.

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