Process for making a lithiated lithium manganese oxide spinel

The invention relates to a process for obtaining a lithium oxide and manganese lithium spinel compound having excess lithium, which is used as an active electrochemical component in a secondary electrochemical cell.

Secondary lithium electrochemical cells or rechargeable cells are known, which have an intercalation compound containing Li as a positive electrode and carbon, usually graphite, as a negative electrode, separated by a non-aqueous electrolyte containing lithium ions. An active cathodic electrochemistry component uses a lithium manganese oxide spinel of the general formula: LiMn₂0₄. Graphite lithium interlayer studies have shown that when lithium manganese oxide spinel is used in a lithium ion rechargeable cell, in which the negative anode or electrode is graphite, there is an irreversible loss of capacity during the first recharge cycle. To avoid this situation a larger mass of positive electrode is used [[1+ x) LiMn₂0₄], to compensate for the loss of lithium on the graphite anode during the first cycle. However, increasing the cathode mass is not an effective remedy when considering the efficiency of the implementation. To compensate for the loss of lithium without seriously affecting the mass or volumetric performance characteristics of the cell, the structures of lithium manganese lithium oxide spinel have been developed with excess lithium (Li_{(1 + x)}Mn₂D₄). The excess lithium in the spinelic compound is intended to compensate for the loss of lithium, associated with the negative electrode, while maintaining a lithium quantity requires balancing the reversible capacity of graphite and maintaining a useful energy level in the cell.

While such lithium manganese lithium oxide spinel compounds have proved to be a useful and effective cathodic material in secondary or rechargeable electrochemical cells, the known methods for obtaining Li spinel_{(1 + x]}Mn₂0₄ they are expensive and difficult at higher levels than the laboratory ones up to commercial volumes. A known method is the LiMn submission₂0₄ one reduction reaction with a heated solution of lithium iodide (Lil) in acetonitrile, another one reduces the manganese lithium oxide spinel with a solution of lithium r -butyl (n-BuLi) in hexane. Both reagents containing lithium are expensive prohibitively, the process of obtaining them involving organic solvents and, in addition, n-BuLi having pyrophoric properties. For these reasons, a viable method is needed for the commercial production of lithium manganese lithium oxide spinel.

The process according to the invention eliminates the disadvantages of known processes, in that it comprises the reaction between a lithium manganese spinel oxide of the formula LiMn₂A₄with a lithium carboxylate, at a temperature between 150 ° C and 350 ° C, preferably 150 ° C and 300P C, in an inert atmosphere, for a period of time between 10 min and 15 h, preferably 2 and 8 h.

The process according to the invention has the advantage of obtaining a lithium oxide and manganese lithium spinel used as a positive electrode in an electrochemical cell that balances the reversible capacity of graphite and maintains a useful energy level in the cell.

Further details of the process according to the invention are given below.

The process according to the invention provides a lithium manganese lithium oxide spinel of formula Li_{(1 + x)}Mn₂0₄, in which □ <x <1; preferably the value of x varies between □, □ 5 and 1.0, preferably between 0.05 and 0.3. The process is carried out at a reaction temperature sufficient for the decomposition of lithium carboxylate and for the formation of the lithium spinelic compound, but below about 350 ° C to avoid the decomposition of the spinelic compound. At about 300 ° C, the spinelic compound begins to decompose into non-spinel decomposition products, such as Li_{(1 + x)}MnO₃ and Mn0₂ which can be used as cathodic components in a secondary electrochemical cell with

RO 115348 Lithium bl. The reaction temperature generally ranges from about 150 ° C to about 50 about 300 ° C, preferably from about 230 ° C to about 250 ° C.

The reaction time is dependent on the choice of the reactants and the reaction temperature. In general, the reaction time varies from about 10 min to about 15 h, preferably from about 2 to about 8 h, as such times have been observed to lead to favorable results. Preferably, the synthesis is conducted 55 in an inert atmosphere, to avoid oxidation reactions leading to the formation of unsupported by-products for use in the electrochemistry cathode composition, such as Li₂CB₃ and / or L ^ MnOg. The inert atmosphere may be composed of noble gases (He, Ne, Ar, Kr, Xe and Rn], vacuum and ion combination. Argon atmosphere is preferred.

The lithium carboxylate used can be any lithium salt of a mono- or 60-polycarboxylic acid, which has a decomposition temperature below 300 ° C and which is effective in lithium spinel LiMn₂0₄ by heating to a temperature below 300 ° C. Examples of suitable carboxylates include lithium acetate, lithium citrate, lithium formate, lithium lactate and other lithium carboxylates, wherein the carboxylate group is linked to a group that attracts electrons to methyl, such as hydrogen, perfluoro-65 alkyl, CF₃S0₂CH₂ and (CF₃SO₂]₂N, etc. Lithium acetate is especially preferred. The process according to the invention can be practiced using different techniques. In one embodiment, the LiMn spinel₂0₄ it is first mixed with a solution, preferably aqueous, of lithium carboxylate, to form a paste. The paste is then dried to remove the solvent and the intimate mixture formed by such spinel and carboxylate is heated to a temperature and time sufficient to decompose the carboxylate and initiate the reaction to form spinel Li (i)._{+ X}) Mn₂0₄.

In another embodiment of the process, LiMn spinel₂0₄ and lithium carboxylate are mixed in the dry process to form an intimate mixture. The intimate mixture is then heated to lithium spinel, forming the product 75 Li_{(1 + x]}Mn₂0₄ wanted. Any dry mixing technique can be used to form a mixture of reactants. Such techniques include roller mixers, ball mixers, bars, etc. In a preferred process, lithium acetate is dissolved in water and lithium manganese oxide spinel is added to the solution to form a paste. LiOAc / LiMn paste₂0₄ it is then dried in air at a temperature of 50 ° C to 80 to 150 ° C, preferably around 100 ° C. The dry mixture is then reacted to heating in an argon atmosphere at a temperature of 230 ° C to 250 ° C for about 2 to 8h.

Following are examples of embodiments of the invention.

Example 1. The lithium spinel of formula Li₁ , Μη ^ is prepared by dissolving 85 of 1.695 g of lithium acetate (LiOAc) in about 30 ml of deionized water (AD). A stoichiometric quantity of 30 g lithium manganese spinel granules is added to the LiOAc solution and the resulting suspension is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the LiOAc reagent, while the suspension is heated to 80 ... 90 ° C for about 3 hours to remove excess 90 water and turn the slurry into a paste. The paste is then dried in vacuo at 80 ° C. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream, from room temperature at 250 ° C for 1.5 hours and left at this temperature for 2 hours, to form a product in the form of black powder - blue. The powder is cooled to 110 ° C for 3 hours in argon stream. In 95 during the reaction the water condensates in the end part of the tubular furnace. Weight loss during the reaction is about 17 ... 20% of the combined weights of LiOAc and spinel. The powdered spinel is analyzed by absorption

RO 115348 Atomic blast (AA) for the concentration of Li and Mn and characterized by X-ray powder diffraction (XRD) analysis.

Example 2. The lithium spinel of the formula 0 \, /η / Ι, is prepared from lithium acetate by dissolving 3.39 g of LiOAc in about 30 ml deionized water (ADJ. A stoichiometric amount of spinel is added to the LiOAc solution. Limnos₂0₄ granules, 30 g, and the resulting suspension is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the LiOAc reagent while the suspension is heated to 80 ... 90 ° C for about 3 hours to remove excess water and turn the slurry into a paste. The paste is then dried in vacuo at 80 ° C. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream at room temperature at 250 ° C for 1.5 hours and left at this temperature for 2 hours to form the product Li, Μη ^ below blue powdered black. The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction the water condenses into the end portion of the tubular furnace. Spinel Li-!₂Mn₂0₄ in powder form it is characterized by X-ray powder diffraction (XRD) analysis and analyzed by atomic absorption (AA) for the concentration of Li and Mn to confirm its structure.

Example 3. The lithium spinel of formula Li₂Mn₂0₄ is prepared by dissolving 16.95 g of lithium acetate (LiOAc) in about 30 ml deionized water (AD). A stoichiometric amount of LiMn spinel is added to the LiOAc solution₂0₄ granules, 30 g, and the resulting slurry is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the LiOAc reagent while the slurry is heated to 80 ... 90 ° C for about 3 hours, to remove excess of water until the suspension turns into a paste. The paste is then dried in vacuo at 80 ° C. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream, from room temperature to 250 ° C for 1.5 hours and left at this temperature for 2 hours. The powder is cooled to 110 ° C for for 3 h in argon stream. During the reaction, the water condenses into the end portion of the tubular furnace. A color change from black-blue to brown is observed during the reaction and the Li spinel product₂Mn₂0₄ it has a brown color, which differs from the black-blue color of the LiMn reactive spinel₂0₄. His spine₂Mn₂0₄ in powder form it is characterized by X-ray powder diffraction (XRD) analysis and analyzed by atomic absorption (AA) for the concentration of Li and Mn.

Example 4. The lithium spinel of formula 0 ^ jMn₂0₄ is prepared by dissolving 3.482 g of lithium citrate in about 30 ml of deionized water (AD). A stoichiometric amount of LiMn is added to the lithium citrate solution₂0₄, 30 g, and the resulting slurry is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the lithium citrate reagent. The suspension is heated to 80 ... 90 ° C for about 3 hours, with stirring, to remove excess water until the suspension turns into a paste. The paste is then dried in vacuo by heating at 80 ° C for 3 h. The resulting powder is lightly heated, in a tubular furnace, in the presence of an argon stream at room temperature at 250 ° C for 1.5 hours and left at this temperature for 2 hours to form a product in the form of black-blue powder. The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction the water condenses into the end portion of the tubular furnace. Weight loss during the reaction is around 40 ... 45% of the combined weights of citrate and spinel reagents. The powder is characterized by XRD and analyzed by atomic absorption (AA) for the concentration of Li and Mn to confirm the spinel structure of Li_{3 1}Mn_of0₄.

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Example 5. The lithium spinel of formula Li, ₂Mn₂0₄ is prepared by dissolving 6.964 g of lithium citrate in about 30 ml of deionized water (AD). A stoichiometric amount of LiMn is added to the lithium citrate solution₂0₄, 30 g, and the resulting slurry is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and lithium citrate reagents. The slurry is heated to 80 ... 90 ° C for about 3 hours under stirring, to remove excess water until the slurry turns into a paste. The paste is then dried in vacuo by heating at 80 ° C for several hours. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream at room temperature at 250 ° C for 1.5 hours and is left at this temperature for 2 hours to form a powdered product. The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction the water condenses into the end portion of the tubular furnace. A color change from black-blue to brown is observed during the reaction and the powdered product has a brown color, which differs from the black-blue color of the LiMn reactive spinel.₂0₄. The powder is characterized by XRD and analyzed for the concentration of Li and Mn, to confirm its structure as Li spinel,₂Mn₂0₄.

Example 6. The lithium spinel of formula Li₂Mn₂0₄ is prepared by dissolving 34.82 g of lithium citrate in about 30 billion deionized water (AD). A stoichiometric amount of LiMn is added to the lithium citrate solution₂0₄ granules, 30 g, and the resulting slurry is stirred to keep the spinel in suspension and to ensure homogeneity between spinel and lithium citrate reactants while the slurry is heated to 80 ... 90 ° C for about 3 hours under stirring, to remove excess water until the suspension turns into a paste. The paste is then dried under vacuum by heating at 80 ° C for 3 hours. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream at room temperature at 250 ° C for 1.5 h and left at this temperature for 2 h to form a powdered product. . The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction the water condenses into the end portion of the tubular furnace. A color change from black-blue to brown is observed during the reaction and the powdered product has a brown color, which differs from the black-blue color of the LiMn reactive spinel.₂0₄. The powder is characterized by X-ray powder diffraction (XRD) and analyzed by atomic absorption (AA) for the concentration of Li and Mn, to confirm the spinel structure of Li₂Mn₂0₄.

Example 7. The lithium spinel of formula Li,, Mn₂D₄ is prepared by dissolving 1,591 g of lithium lactate in about 30 ml of deionized water (AD). A stoichiometric amount of LiMn is added to the lithium lactate solution₂0₄ granules, 30 g, and the resulting slurry is stirred to keep the spinel in suspension and to ensure homogeneity between spinel and lithium lactate reactants while the slurry is heated to 8O ... 9O ° C for about 3 h, to remove excess water until the slurry turns into a paste. The paste is then dried in vacuo at 80 ° C. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream at room temperature at 250 ° C for one hour and left at this temperature for 2 hours to form a powdered product. The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction the water condenses into the end portion of the tubular furnace. Weight loss during the reaction is about 20% of the combined weights of dairy and spinel reagents. The powder is characterized by X-ray powder diffraction (XRD) and atomic absorption (AA) analysis for the concentration of Li and Mn, to confirm the spinel structure of Li,, Mn₂0₄.

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Example 8. Lithium spinel of formula 1¾ ₂Mn₂0₄ is prepared by dissolving 3.182 g of lithium lactate in about 30 ml deionized water (AD). A stoichiometric amount of LiMn is added to the lithium lactate solution₂0₄ granules, 30 g, and the resulting suspension is stirred to keep the spinel in suspension and to ensure homogeneity between spinel reactants and lithium lactate, while the suspension is heated to 80 ... 90 ° C for about 3h, to remove excess water until the slurry turns into a paste. The paste is then dried in vacuo at 80 ° C. The resulting powder is lightly heated in a tubular furnace in the presence of an argon stream, from room temperature to 250 ° C for one hour, and left at this temperature for 2 hours to form a black-blue powder product. . The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction, the water condenses into the end portion of the tubular furnace. The powder is characterized by X-ray powder diffraction (XRD) and analyzed by atomic absorption (AA) for the concentration of Li and Mn, to confirm the structure as a spinel. ₂Mn₂0₄.

Example 9. The lithium spinel of formula Li₂Mn₂0₄ is prepared by dissolving 15.91 g of lithium lactate in about 30 ml deionized water (AD). A stoichiometric amount of LiMn is added to the lithium lactate solution₂0₄ granules, 30 g, and the resulting slurry is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and lithium lactate reactants while the slurry is heated to 80 ... 90 ° C for about 3h, to remove excess water until the suspension turns into a paste. The paste is then dried in vacuo at 80 ° C. The resulting powder is lightly heated in a tubular furnace, in the presence of an argon stream at room temperature at 250 ° C for one hour and left at this temperature for 2 hours to form a powdered product. The powder is cooled to 110 ° C for 3 hours in argon stream. During the reaction the water condenses into the end portion of the tubular furnace. A color change from blackish-blue to brown is observed during the reaction and the powdered product has a brown color, which differs from the black-blue color of the LiMn reactive spinel.₂0₄. The powder is characterized by X-ray powder diffraction (XRD) and analyzed by atomic absorption (AA) for the concentration of Li and Mn, to confirm the spinel structure of Li₂Mn₂0₄