MXPA97009535A - Improved process for the manufacture of a lithium-manganese litificum oxide spinela - Google Patents

Abstract

Described is a process for the manufacture of a lithium-manganese lithium-manganese spinel, formula: Li (1 + x) Mn2O4, comprising contacting a lithium manganese oxide spinel of the formula: LiMn2O4, with a lithium carboxylate compound at a temperature and for a time sufficient to decompose the carboxylate compound and liberate the lithium to form the vitrified spinel

Description

IMPROVED PROCESS FOR THE MANUFACTURE OF A LITHIUM OXID SPINEL - LITIFIED MANGANESE FIELD OF THE INVENTION The present invention relates to an improved process for the manufacture of a lithium spinel compound. In particular, the invention relates to a process for the lithification of a spinel of lithium manganese oxide to form a spinel having as characteristic lithium in excess, which is useful as an electrochemically active component in a secondary electrochemical cell. Electrochemical lithium cells, secondary cells or rechargeable cells typically include a lithium intercalation compound as a positive electrode and a negative carbon electrode, typically graphite, separated by a non-aqueous lithium ion electrolyte. A spinel of lithium manganese oxide of general formula LiMn2 4 4 has been commonly employed as the electrochemically active cathode component. Studies of the intercalation of lithium to graphite have shown, however, that when the lithium manganese oxide spinel is used in a rechargeable lithium ion cell, in which the negative electrode or anode is graphite, there is a marked irreversible loss , detrimental in capacity during the first recharge cycle. The initial procedure to overcome this problem is simply to use a larger mass of the positive electrode [(i + X) LiMn20] to compensate for the loss of lithium on the graphite anode during the first cycle. However, the increase in cathode mass is not an effective solution when efficiency in performance is taken into consideration. In order to eliminate the loss of lithium without seriously undesirably impacting the characteristics of basic or volumetric performance of the cell, lithium manganese lithium oxide spinel structures have been developed which have lithium in excess ( Li (i + X) Mn2? 4). This excess lithium in the spinel compound is available to compensate for the initial loss of lithium associated with the negative electrode, while reserving an amount of lithium needed to balance the irreversible capacity of the graphite and maintain a useful energy level in the cell . While such lithium manganese oxide spinel compounds have proved to be useful and an effective cathode material in secondary or rechargeable electrochemical cells, the presently known methods for producing the spinel of Li (i + X) Mn2 ? 4, are expensive and difficult to scale from laboratory size to commercial volume. One such production method, for example, includes subjecting LiMn2Δ4 to a reduction reaction with a heated solution of lithium iodide (Lil) in acetonitrile; another involves the reduction of the spinel of lithium manganese oxide with a solution of n-butyl lithium (n-BuLi) in exano. Both of these reagents containing lithium are prohibitively expensive, the production processes involve organic solvents and also, the (n-BuLi) has dangerous pyrophoric properties. Therefore, there is a need for a viable method for the commercial production of lithium manganese lithium oxide spinel. It has now been discovered that lithium manganese lithium oxide spinel of the formula Li (1 + X) Mn2 4] can be economically manufactured by a simple method, which comprises contacting a lithium manganese oxide spinel of the formula Li n2? 4 with a lithium carboxylate compound, at a temperature and for a time sufficient to decompose the carboxylate compound and liberate the lithium from the lithiated form, the spinel of ü (i +?) Mn2O4. It has been found that this Jitified spinel is particularly useful as the positive electrode of a secondary lithium ion electrochemical cell. The process of the present invention produces a lithium manganese lithium oxide spinel of the formula Li (i + X) Mn2? , where 0 <; x < 1; preferably, the value of x ranges from about 0.05 to about 1.0; more preferably, x ranges from about 0.05 to about 0.3. The process is carried out at a reaction temperature sufficient to decompose the lithium carboxylate reagent and form the lithiated spinel compound, but less than about 350 ° C to prevent decomposition of the spinel compound. At a temperature greater than about greater than 300 ° C, the spinel compound begins to decompose into decomposition products that do not consist of spinel, such as Li (i + X) Mn 3 and MnO 2 which are not useful as the components of the cathode in a secondary lithium electrochemical cell. The reaction temperature generally ranges from about 150 ° C to about 300 ° C; preferably, the reaction temperature ranges 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 ranges from about 10 minutes to about 15 hours; preferably about 2 to about 8 hours of reaction time is employed, since it has been found that such times provide favorable results. Preferably, the synthesis is carried out in an inert atmosphere to avoid the oxidation reactions resulting in the formation of undesirable byproducts for the utility of the electrochemical cathode, such as LÍ2CB3 and / or Li (i-X) Mn? 3. Suitable inert atmospheres include the noble gases (helium, neon, argon, krypton, zenon and radon) and combinations thereof and the like. An argon atmosphere is preferred. The lithium carboxylate reagent used in the present process is any lithium salt of mono or polycarboxylic acids, which have a decomposition temperature of less than about 300 ° C and which are effective for lithium or lithium lithium spinel. n2O4 when heated in contact with the spinel at a temperature less than about 300 ° C. Examples of suitable lithium carboxylates, useful in the present process, include lithium acetate, lithium citrate, lithium formate, lithium lactate, other lithium carboxylates in which the carboxylate group is attached to a group that is electron extractor , in relation to methyl (such as hydrogen, perfluoroalkyl, CF3SO2CH2 and (CF3SO2) 2N) and the like. Lithium acetate is particularly preferred as the lithium carboxylate reagent. The process of the present invention can be carried out by using various techniques. In one embodiment, the spinel of LiMn2O4, in particles, is first mixed with a solution, preferably an aqueous solution of lithium carboxylate to form a paste. Then, the paste is dried to remove the solvent and the intimate mixture thus formed of the spinel and carboxylate is heated at a temperature and for a time sufficient to decompose the carboxylate and initiate the reaction to form the spinel of Li (i + x) Mn2? 4. In another alternative embodiment of the process, the LiMn2O spinel, particulate and the lithium carboxylate salt are mixed dry to form an intimate mixture. The dried mixture is then thermally treated to lithify or clean the spinel to form the desired Li (i + X) Mn2 ?4 product. Any suitable dry mixing technique can be used to form the reaction mixture; such techniques include drum mixers, ball mixers, roller mixers and the like. In a preferred process, lithium acetate; as the lithium carboxylate reagent, it is dissolved in water and the spinel of lithium manganese oxide is added to the solution to form a paste. Then the pasta LiOAc LiMn2O4 is dried in air at a temperature of about 50 ° C to about 150 ° C, preferably about 100 ° C. The dried mixture is then reacted by heating in an argon atmosphere at a temperature of about 230 ° C to about 250 ° C for a period of about 2 to about 8 hours. The following examples are provided to further illustrate the invention.

Example 1 A lithium spinel of formula L! 1Mn204, prepare to dissolve 1. 695 g. of lithium acetate (LiOAc). In approximately 30 ml. of deionized water (DI). A stoichiometric amount of LiMn2? 4 spinel of particulate lithium manganese oxide, 30 grams, is added to the LiOAc solution and the resulting suspension of stirring to keep the spinel in suspension and to ensure homogeneity between the spinel and the LiOAc reagents, while the suspension is heated to a temperature of 80-90 ° C for about 3 hours to remove the excess water and to convert the suspension into a paste. The paste is then dried under vacuum at a temperature of 80 ° C. The resulting powder is slowly heated, in a tube furnace in the presence of argon flowing from room temperature to a temperature of 250 ° C, for a period of 1.5 hours and held at that temperature for 2 hours to form a product in bluish black powder. The powder is cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, water condenses at the downstream end of the tube furnace. The weight loss during the reaction is approximately 17-20% of the combined prisoner of the LiOAc and the spinel reagents. The powder product of Li? .1 n2O4 spinel is analyzed by atomic absorption (AA) for the concentration of lithium and manganese and is characterized by pulvidifractometry analysis (XRD).

Example 2 A lithium spinel of formula U? .2Mn2? l is prepared from lithium acetate, by dissolving 3.39 g. of LiOAc, in approximately 30 ml. of deionized water. A stoichiometric amount of the LiMn2O4 spinel, particulate, 30 g., 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 reagents. , while heating to a temperature of 80-90 ° C for about 3 hours to remove excess water until the slurry becomes a paste. The paste is then dried under vacuum at a temperature of 80 ° C. The resulting powder is slowly heated, in a tube furnace in the presence of flowing argon, from room temperature to 250 ° C, for a period of 1.5 hours and held at that temperature for 2 hours to form the spinel product Li1 2Mn2O4, a blue-white powder. The powder is cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, water condenses at the downstream end of the tube furnace. The Li? .2Mn2? 4 spinel powder is characterized by a pulvifractometry analysis (XRD) and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure.

EXAMPLE 3 A lithiated spinel of formula LY2Mn2O4 is prepared by dissolving 16.95 g. of lithium acetate (LiOAc) in about 30 ml. of deionized water (DI). A stoichiometric amount of LiMn2? 4 spinel in 30 g particles 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 reagents, as long as the suspension is heated to a temperature of 80-90 ° C during about 3 hours to separate the excess water, until the suspension becomes a paste. The paste is then dried under vacuum at a temperature of 80 ° C. The resulting powder is slowly heated, in a tube furnace in the presence of flowing argon, from room temperature to a temperature of 250 ° C, for a period of 1.5 hours and maintained at that temperature for 2 hours. The powder is cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, water condenses at the downstream end of the furnace. A color change from bluish black to brown is observed during the reaction and the spinel product of Li2Mn2O4 has a brown color which is different from the bluish black color of the spinel reagent of LiMn2O4. The spinel powder Li2Mn2O4 is characterized by a pulvidiafractometry analysis (XRD) and analyzed by atomic absorption (AA) for the concentration of lithium and manganese.

Example 4 A lithium spinel of formula Li?.? Mn2? is prepared by dissolving 3,482 g. of lithium citrate in approximately 30 ml. of deionized water. A stoichiometric amount of LiMn2O4, 30 g. it is added to the lithium citrate solution and the resulting suspension is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the lithium citrate reagents. The suspension is heated to a temperature of 80-90 ° C for about 3 hours, while stirring to remove excess water until the suspension becomes a paste. The pulp is then dried by heating at 80 ° C for about 3 hours. The resulting powder is heated slowly, in a tube furnace in the presence of flowing argon, from room temperature to a temperature of 250 ° C for a period of 1.5 hours and is maintained at that temperature for 2 hours to form a product in bluish-black powder. The powder is then cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, the water condenses at the downstream end of the flowing tube furnace, the weight loss during the reaction being about 40-45% of the combined weight of the citrate and spinel reagents. The powder is characterized by XRD and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure as a spinel of Li1.?Mn2O4.

Example 5 A lithium spinel of formula Li? 2Mn2O is prepared by dissolving 6,964 g. of lithium citrate in approximately 30 ml. of deionized water. A stoichiometric amount of LiMn2O4, 30 g. it is added to the lithium citrate solution and the resulting suspension is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the lithium citrate reagents. The suspension is heated to a temperature of 80-90 ° C for about 3 hours, while stirring to remove excess water until the suspension becomes a paste. The paste is then dried by heating at 80 ° C for a few hours. The resulting powder is heated slowly, in a tube furnace in the presence of flowing argon, from room temperature to a temperature of 250 ° C for a period of 1.5 hours and is maintained at that temperature for 3 hours to form a product in dust. The powder is then cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, the water condenses at the downstream end of the flowing tube furnace. A change in color from bluish black to brown during the reaction is observed and the powder has a brown color which is different from the bluish black color of the LiMn2 spinel reagent? . The powder is characterized by XRD and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure as Li1 2 n2O4 spinel.

Example 6 A lithium spinel of the formula Li2Mn204 is prepared by dissolving 34.82 g. of lithium citrate in approximately 30 ml. of deionized water. A stoichiometric amount of LiMn204, 30 g. it is added to the lithium citrate solution and the resulting suspension is stirred to keep the spinel in suspension and to ensure homogeneity between the spinel and the lithium citrate reagents, while the suspension is heated to a temperature of 80 -90 ° C for about 3 hours to remove excess water until the suspension becomes a paste. The paste is then dried by heating at 80 ° C for a few hours. The resulting powder is slowly heated, in a tube oven in the presence of flowing argon, from room temperature to a temperature of 250 ° C for a period of 1.5 hours and maintained at that temperature for 2 hours to form a product in dust. The powder is then cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, the water condenses at the downstream end of the flowing tube homo. A color change from bluish black to brown during the reaction is observed and the powder has a brown color which is different from the bluish black color of the LiMn2O4 spinel reagent. The powder is characterized by XRD and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure as spinel of Li2Mn2O4.

Example 7 A lithium spinel of formula L? Mn2O4 is prepared by dissolving 1. 591 g. of lithium lactate in approximately 30 ml. of deionized water. A stoichiometric amount of LiMn2O4, 30 g. it 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 reagents, while heating to a temperature of 80-90 ° C for about 3 hours. hours to separate the excess water until the suspension becomes a paste. The paste is then dried by heating at 80 ° C for a few hours. The resulting powder is heated slowly, in a tube oven in the presence of flowing argon, from room temperature to a temperature of 250 ° C for a period of 1 hour and maintained at that temperature for 2 hours to form a product in dust. The powder is then cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, the water condenses at the downstream end of the flowing tube homo. The weight loss during the reaction is approximately 20% of the combined weight of lithium lactate and spinel reagents. The powdered product is characterized by XRD and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure as spinel of Li?.? Mn2O4.

Example 8 A lithium spinel of formula L? 2Mn 2 O 4 is prepared by dissolving 3,182 g. of lithium lactate in approximately 30 ml. of deionized water. A stoichiometric amount of LiMn2O4 spinel, in particles, 30 g. it 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 reagents, while the suspension is heated to a temperature of 80-90 ° C. for about 3 hours to separate the excess water until the suspension becomes a paste. The paste is then dried by heating at 80 ° C. The resulting powder is slowly heated, in a tube furnace in the presence of flowing argon, from room temperature to a temperature of 250 ° C for a period of 1 hour and maintained at that temperature for 2 hours to form a product in bluish black powder. The powder is then cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, the water condenses at the downstream end of the flowing tube homo. The powdered product is characterized by XRD and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure as Li? .2 n2O4 spinel.

Example 9 A lithium spinel of formula Li2 n2? 4 is prepared by dissolving 15.91 g. of lithium lactate in approximately 30 ml. of deionized water. A stoichiometric amount of spinel of LiMn204l in particles, 30 g. it 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 reagents, while the suspension is heated to a temperature of 80-90 ° C. for about 3 hours to separate the excess water until the suspension becomes a paste. The paste is then dried by heating at 80 ° C. The resulting powder is slowly heated, in a tube furnace in the presence of flowing argon, from room temperature to a temperature of 250 ° C for a period of 1 hour and maintained at that temperature for 2 hours to form a product in dust. The powder is then cooled to a temperature of 110 ° C for a period of 3 hours in an atmosphere of flowing argon. During the reaction, the water condenses at the downstream end of the flowing tube furnace. A color change from bluish black to brown during the reaction is observed and the product has a brown color which is different from the bluish black color of the LiMn2O4 spinel reagent. The powdered product is characterized by XRD analysis and analyzed by atomic absorption (AA) for the concentration of lithium and manganese to confirm its structure as spinel of Li2Mn2O4. It is noted that in relation to this date, the best method known to the applicant, to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. Claims 1. A process for the preparation of lithium lithium manganese lithium spinel compound, lithium, of the formula Li (? + X) Mn2? 4, wherein 0 < x < 1, characterized in that it comprises reacting a spinel compound of manganese lithium dioxide of the formula LiMn2O, with a lithium carboxylate at a temperature and for a sufficient time to decompose the carboxylate and form the lithiated spinel.
2. 2. The process according to claim 1, characterized in that the selected lithium carboxylate is selected from the group consisting of lithium acetate, lithium citrate, lithium lactate and other lithium carboxylates in which the carboxylate group is attached to a group that is extractor of electrons in relation to methyl.
3. 3. The process according to claim 2, characterized in that the lithium carboxylate is lithium acetate.
4. 4. The process according to claim 1, characterized in that the reaction is carried out at a temperature between about 150 ° C at a temperature less than about 350 ° C.
5. 5. The process according to claim 4, characterized in that the temperature fluctuates from about 150 ° C to a temperature of less than about 300 ° C.
6. 6. The process according to claim 1, characterized in that the reaction time fluctuates from about 10 minutes to about 15 hours.
7. 7. The process according to claim 5, characterized in that the reaction time ranges from about 2 to about 8 hours.
8. 8. The process according to claim 1, characterized in that the reaction is carried out in an inert atmosphere.
9. 9. The process according to claim 1, characterized in that the spinel compound of lithium manganese dioxide is reacted with lithium acetate at a temperature of about 230 ° C to about 250 ° C, for a period of about 2 to about 8. hours in an atmosphere of inert argon.
10. 10. A spinel compound of lithium manganese dioxide, lithium of the formula Li (i + X) Mn2? 4, wherein 0 < x < 1, characterized in that it is prepared according to the process according to claim 1.