MXPA00005916A - Lithium manganate, method of producing the same, and lithium cell produced by the method - Google Patents

Abstract

A lithium manganate useful as an active material of the positive plate of a lithium cell, a method for producing the same, a positive plate for a lithium cell comprising an active material of lithium manganate, and a lithium cell are provided. The lithium manganate is cubic particles and the particles have pores therein. Therefore lithium cell comprising such an active material of lithium manganate has a high initial discharge capacity of over 95 mAh/g and an excellent cycle characteristic.

Description

LITHIUM MANGANATE, PROCEDURE TO PRODUCE IT AND LITHIUM BATTERIES THAT USE THE LITHIUM TECHNICAL FIELD The present invention relates to lithium manganese, which is a compound useful as an active material for the positive electrode of a lithium battery, to a process for producing it, to a positive electrode for a lithium battery using the same, as an active material, for this positive electrode, and to a lithium battery.

PREVIOUS TECHNIQUE Lithium manganese is a compound represented by the formula LixMny04, and representatives of this are the spinel-type, LiMn20-, Li4 / 3Mn5 / 304 and the like. To obtain these lithium manganates, a process of calcining a mixture of a manganese compound and a lithium compound at a temperature of approximately sxrs is used. EXCUSE OF THE INVENTION The lithium manganate, obtained by the conventional process above, it is apt to become a sintered body, in which a non-uniform sintering occurs between the particles, because a mixture of a manganese compound and a lithium compound is calcined at approximately 800 ° C, in order to to adjust the valence of manganese or the decrease of by-products. Thus, there is a problem that the size of the particles can not be controlled. Also, since a mixture of a manganese compound and a lithium compound is lower in reactivity, even when calcined at high temperatures, the uniform composition can hardly be obtained and there are many crosslinking effects. In order to avoid these problems, the mechanical calcining or grinding must be repeated many times. Likewise, the secondary lithium batteries, which use the lithium manganese, obtained by the previous process, as an active material for positive electrodes, are not only low in initial charge capacity and discharge, but also show a marked reduction in capacity with repetition of loading and unloading. This is because the crystals of lithium manganese are crushed at the time of loading and unloading, which is considered to be caused by the presence of crosslinking defects and the low conductivity of lithium ions. For the solution of the above problems, a process has been proposed, which comprises impregnating a porous manganese dioxide with lithium acetate, lithium nitrate or lithium hydroxide, and obtaining a product of uniform composition at low temperatures (e.g. , "Electrochemistry (Denki Kagaku)", 63, 941 (1995)), but this process is still not enough. The inventors have made intensive investigations in an attempt to obtain a lithium manganese useful as active material for positive electrodes of lithium batteries. As a result, it has been found that secondary lithium batteries, in which an active material is used for the positive electrodes, comprising the lithium manganese which has a cubic particle shape and contains voids in these particles, are high in the initial capacity of loading and unloading and excellent in the characteristics of the cycle, after the repetition of loading and unloading. After further investigations, the present invention has been carried out. That is, the present invention relates to a lithium manganese, which has a cubic particle shape and- provides an initial discharge capacity of at least 95 mAh / g, which is used as an active material for the positive electrodes of lasa lithium batteries. Also, the present invention relates to a process for the advantageous production of lithium manganese and the first process is characterized by including a step of reacting a manganese compound with an alkali, to obtain a manganese hydroxide, an oxidation step of the hydroxide in an aqueous medium or a gas phase, to obtain the manganese oxide, a step of reacting this manganese oxide with a lithium compound in an aqueous medium, to obtain a precursor of the lithium mánganate, and a step of calcining the precursor with the heating, to obtain the lithium manganate. The second process is characterized by including a step of reacting a manganese compound with an alkali, to obtain a manganese hydroxide, a step of oxidizing the hydroxide in an aqueous medium or a gas phase, to obtain a manganese oxide, a step of reacting the manganese oxide with an acid, in an aqueous medium, to substitute protons of part of the manganese and to obtain a substituted manganese oxide in the protons, a step of reacting the manganese oxide, substituted in the protons, with a compound of lithium in an aqueous medium, to obtain a precursor of the lithium manganate, and a step of calcining the precursor with heating, to obtain the lithium manganese. The present invention further relates to a positive electrode for a lithium battery, in which the above lithium manganese is used as an active material for the positive electrode and to a lithium battery using this positive electrode.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an X-ray diffraction diagram of a sample a. Figure 2 is a ray diffraction diagram X of sample A. - - - Figure 3 is an electron scanning microphotograph (amplification of 50,000), which shows the particle structure of sample A.

Figure 4 is an electron scanning photomicrograph (amplification of 50,000), showing the particle structure of sample C. Figure 5 is an electron transmission photomicrograph (amplification of 50,000), showing the particle structure of sample A. Figure 6 is an electron diffraction photograph of sample A. Figure 7 is an electron scanning microphotograph (amplification of 50,000), showing the particle structure of sample L.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a lithium manganese that has a cubic particle shape and contains voids in the particles and provides an initial discharge capacity of at least 95 mAh / g, preferably at least 100 mAh / g, when used as an active material for positive electrodes of lithium batteries. The lithium manganese can be single-phase or it can be a mixture containing the lithium manganese and impurities, which come from the production stages, such as manganese oxide, as long as the aforementioned discharge capacity is at less than 95 mAh / g. If the discharge capacity is lower than the previous interval, the amount of lithium manganese, necessary to obtain batteries of the desired capacity, increases and this is not industrially preferred. The lithium manganate of the present invention is a compound represented by the formula LixMny04, and the values of X and y in the formula are preferably in the range of 0.3 to 1.5, expressed by the value of x / y. As preferred compositions, mention may be made, for example, of Li n204 and LÍ4 / 3Mns / 304, spinel-type and LiMn02 of rock-salt type in layers. The shape of cubic particles means a cubic shape such as a die or a rectangular parallelogram shape, and the particles include those having angles, i.e., vertices, or sides that are partially removed. All individual particles do not necessarily have the same shape, as they are composed mainly of cubic particles, the amorphous particles may be partially contained. The presence of voids in the particles can be confirmed by measuring the void content, and when this content is 0.005 ml / g or more, it can be admitted that the particle contains voids. This void content is preferably 0.01 to 1.5 ml / g and more preferably 0.01 to 0.7 ml / g. Also, the initial discharge capacity is at least 95 mAh / g, when the lithium manganese is used as an active material for positive electrodes of lithium batteries, which can be confirmed by carrying out the measurement on the battery status and under the measurement conditions, mentioned below. Employing the above construction, the secondary lithium batteries, which contain the lithium manganese of the present invention, as an active material of the positive electrodes, are high in initial charge and discharge capacity, and excellent in cycle characteristics. The specific surface area of the lithium manganese is preferably 1 to 100 m / g, more preferably 1 to 30 m2 / g. Since this interval is preferred for the lithium insertion reaction, when lithium manganese is used for the positive electrodes of the lithium batteries, no crushing of the crystals occurs at the time of loading and unloading, and Battery characteristics are excellent. The particle diameter is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm. The particle diameter can be measured by reading the maximum length of the individual particles, in an electron photomicrograph. With respect to the process of producing the lithium manganate, according to the present invention, the first production process is characterized in that it includes: (1) a step of reacting a manganese compound with an alkali, to obtain a manganese hydroxide; (2) a step of oxidizing the hydroxide in an aqueous medium or a gas phase, to obtain a manganese oxide; (3) a step of reacting the manganese oxide with a lithium compound in water, to obtain a precursor of the lithium manganese; Y (4) a step of calcining the precursor with heating, to obtain a lithium manganese. The second production process is characterized in that it includes: (1) a step of reacting a manganese compound with an alkali, to obtain a manganese hydroxide; (2) a step of oxidizing the hydroxide, in an aqueous medium or a gas phase, to obtain a manganese oxide; (2) 'a step of reacting the manganese oxide with an acid, in an aqueous medium, to replace protons for a part of the manganese and obtain substituted manganese oxide in the protons; (3) a step of reacting - the manganese oxide, substituted in the protons, with a lithium compound, in an aqueous medium, to obtain a precursor of the lithium manganese; and (5) a step of calcining the precursor with heating, to obtain a lithium manganese. Step (1) is that of reacting a manganese compound with an alkali to obtain a manganese hydroxide. The reaction of the manganese compound with alkali may be carried out by reacting a manganese compound, soluble in water, with an alkali, in an aqueous medium or by the reaction of a solution of manganese, which contains ions of Mn2 +, Mn3 + and / or Mn4 +, obtained by dissolving or compound of manganese, hardly soluble in. water, in or acid, with an alkali in an aqueous medium. The above process of reacting a manganese compound, soluble in water, with an alkali, in an aqueous medium, is more preferred. With the water-soluble manganese compounds, inorganic, water-soluble manganese compounds, such as manganese sulfate, manganese chloride and manganese nitrate, and organic, water-soluble manganese compounds, such as manganese acetate. As the manganese compounds are hardly soluble in water, Mn02 can be used, and its hydrates, Mn203, and its hydrates, manganese oxides, such as MnO and Mn304, and organic manganese compounds, such as alkoxides. of manganese. As the acids used, mention may be made of inorganic acids, such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids, such as acetic acid and formic acid. As the alkalies, alkali hydroxides, such as sodium hydroxide, potassium hydroxide and lithium hydroxide, ammonia compounds, such as ammonia gas and aqueous ammonia, and alkali metal carbonate compounds, such as ammonia, can be used. Sodium carbonate, potassium carbonate, lithium carbonate and ammonium carbonate. The reaction can be carried out in an atmosphere of air or an inert gas, but is preferably carried out in an atmosphere of an inert gas, in order to control the oxidation level of the manganese hydroxide. The reaction temperature is preferably 10 to 80 ° C to control the particulate form. ~~ The resulting manganese hydroxide can be filtered or washed, if necessary. The next step (2) is that of oxidizing the manganese hydroxide, obtained in step (1), in an aqueous medium or a gas phase, to obtain a manganese oxide. The oxidation in the aqueous medium can be carried out by blowing air, oxygen or ozone into the aqueous medium containing the manganese hydroxide, or by adding an aqueous hydrogen peroxide or a peroxodisulfate to the aqueous medium. For example, potassium peroxodisulfate can be used as peroxodisulfate. The oxidation temperature in the aqueous medium is preferably from 10 ° C to the boiling point, more preferably from room temperature to 90 ° C. The oxidation in the gas phase can be carried out by filtering or washing the aqueous medium containing the manganese hydroxide, if necessary, and then drying the manganese hydroxide in the air. The oxidation temperature in the gas phase is preferably from room temperature to 300 ° C, more preferably from 50 to 130 ° C. In the present invention, it is preferred that the manganese hydroxide, obtained in step (1), be: (i) oxidized in an aqueous medium or (ii) first partially oxidized in the aqueous medium and then oxidized in a gas phase. The degree of oxidation of the manganese hydroxide can be optionally adjusted, but it is considered that when the oxidation degree is small, the oxides, hydrated oxides or bivalent, trivalent and tetravalent manganese hydroxides are present in the manganese oxide. Manganese oxides of the preferred state in the present invention comprise 2MnO-Mn02 as a major component, with the mole ratio of Mn2 * / Mn4 * being in the range of 1 to 3. More preferred are manganese oxides having a specific surface area of 10 to 40 m2 / g, a void content of 0.08 to 0.3 ml / g, and a particle diameter of about 0.08 to 0.15 μm, and these manganese oxides react easily with the lithium compound in the next stage (3), due to the large specific surface area and a high content of voids. Such manganese oxides, which have a large specific surface area and a high void content can be obtained by employing the aforementioned preferred oxidizing conditions. In step (1), while the manganese compound reacts with the alkali, for example, while this alkali is added to an aqueous solution of a manganese compound, the oxidation can be carried out with air, oxygen, ozone, aqueous hydrogen peroxide or petsxodisulfate. Step (2) is a step of reacting the manganese oxide, obtained in step (1), with an acid, in an aqueous medium, to obtain a substituted manganese oxide in the protons, which results from the substitution of the protons on the one hand of manganese, and the manganese oxide, replaced e? the protons, is high in reactivity, with the lithium compound in the subsequent step (3) of obtaining a precursor of a lithium manganese, and this is preferred. As the acid, any of the inorganic acids, such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and the like, and water soluble organic acids, such as acetic acid, formic acid and the like, can be used. Among them, inorganic acids, felling such as hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid are preferred, because they are industrially advantageous. The temperature at which the manganese oxide is reacted with the acid is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C. The manganese oxide, thus obtained, can be filtered, washed or dried, if necessary. Step (3) is a step of reacting the manganese oxide or the substituted manganese oxide in the protons, obtained in step (2) or (2) ', with a lithium compound, in an aqueous medium, to obtain a precursor of lithium manganese. As the lithium compound, lithium hydroxide, lithium carbonate or the like can be used, and lithium hydroxide is preferred because it is superior in reactivity. The reaction proceeds by mixing the lithium compound and the manganese oxide in an aqueous medium and maintaining the temperature at 50 ° C or more. The temperature is more preferred at 100 ° C or higher, more preferably at 100 to 250 ° C and especially preferred at 100 to 180 ° C. When the reaction is carried out at a temperature of 100 ° C or more, it is preferred to place the lithium compound and the manganese oxide in an autoclave and subject them to a hydrothermal treatment under a saturated steam pressure or under pressurization. Also, when the lithium compound and the manganese oxide are mixed in an aqueous medium and the mixture is heated, dried and solidified with evaporation of the aqueous medium at 50 ° C or more (evaporation to dryness), the concentration of the lithium in the aqueous medium increases with evaporation of the aqueous medium and, as a result, the precursor of lithium manganate is easily produced in the reaction of the lithium compound and the manganese oxide, and this is preferred. The precursor of the lithium manganate, obtained in step (3), varies in composition, depending on the reaction conditions, but is considered to be a mixture containing mainly a solid solution of 2MnO-Mn02, and Li20-MnO-Mn0, LiMn204, LiMn02, or similar. This can be confirmed by X-ray diffraction. When the reaction in step (3) is carried out by feeding an oxidizing agent by an intermittent or continuous process, the reactivity with the lithium compound increases, and this is preferred. The intermittent process is a process that involves repeating the following operations (1) - (3), until the reaction reaches the desired level: (1) feed a given amount of an oxidizing agent into the reaction system, then (2) carry to the reaction with suspension of the feed of the oxidizing agent until the charged oxidizing agent has been consumed, and (3) measuring the reaction weights of the manganese compound and the lithium compound. The intermittent process is preferred to exactly control the reaction weights of the manganese oxide and the lithium compound. The continuous process is a process to carry out the reaction until it reaches the desired reaction level, continuously feeding the oxidizing agent to the reaction system, with measurement of the reaction level of the manganese oxide and the lithium compound. The continuous process is economically preferred to carry out the reaction on an industrial scale. Also, it is preferred to carry out the reaction using at least one oxidizing agent, selected from air, oxygen, ozone, aqueous hydrogen peroxide and peroxodisulfate, because the reactivity of the lithium compound and the manganese oxide is improved. Like peroxodisulfate, for example, potassium peroxodisulfate can be used. In order to carry out step (3) by the hydrothermal treatment and feed the oxidizing agent by the intermittent process, before the hydrothermal treatment, the air, oxygen or ozone can be blown into the mixture of the lithium compound and the manganese oxide. or the aqueous hydrogen peroxide or peroxodisulfate can be added to the mixture and, in addition, the oxygen can be fed. Also, in the course of the hydrothermal treatment, the temperature is lowered and the air, oxygen or ozone can be blown into the mixture of the lithium compound and the manganese oxide or the aqueous hydrogen peroxide or the peroxodisulfate can be added to the mixture and, in addition, oxygen can be fed. In the case of the continuous process, the hydrothermal treatment is carried out with the continuous feeding of the oxygen gas under pressure. The reaction weights of the manganese oxide and the lithium compound can be obtained by taking a small amount of the reaction mixture and measuring it by the neutralization titration of the alkali concentration of the solution from which the solid matter has been removed. The lithium manganese precursor, obtained in step (3), can also be oxidized by blowing air, oxygen or ozone into the solution containing the lithium manganese precursor or by adding aqueous hydrogen peroxide or peroxodisulfate to the solution. Also, if necessary, the solution can be filtered, washed or dried. The drying temperature can optionally be adjusted within the range less than the temperature at which the precursor of the lithium manganese is converted to this lithium manganese, and is suitably 50 to 200 ° C. Step (4) is a step of heating and calcination of the lithium manganese precursor, obtained in step (3), to obtain a lithium manganese. The temperature for heating and calcination is in the range of the temperature at which the precursor is converted to the lithium manganese up to. the temperature at which the specific surface area of the resulting lithium manganese reaches 1 m? / g or less. "It is considered that TT-T temperature for heating and calcination may vary depending on the composition and particle size of the precursor and the calcination atmosphere, but is generally from 250 to 840 ° C and preferably from 280 to 7O0 ° C, to obtain a fine lithium manganese of good crystallinity, and more preferably from 300 to 600 ° C. Also, a range of 650 to 800 ° C is preferred to obtain the lithium manganese of a large particle diameter. If the calcination temperature is greater than the above range, the lithium in the resulting lithium manganese vaporizes easily. The calcination atmosphere is not limited as long as this atmosphere contains oxygen, such as air, and the partial pressure of oxygen can be adjusted optionally. Next, the present invention relates to a positive electrode for lithium batteries, which use the aforementioned lithium manganese, as an active material for the positive electrode, and furthermore refers to a lithium battery obtained using this positive electrode . The lithium batteries of the present invention include primary batteries, which use lithium metal for negative electrodes, secondary, chargeable and downloadable batteries, which use lithium metal for negative electrodes, and secondary lithium ion batteries, loadable and downloadable, using a carbon material, a tin compound, a lithium titanate and the like, for negative electrodes. In the case of flat batteries, in the form of coins, the positive electrode for lithium batteries can be obtained by adding carbon conductive agents, such as acetylene black, carbon and graphite powders and binders, such as resin of polytetrafluoroethylene and polyvinylidene fluoride, to the lithium manganese powders of the present invention, kneading them and molding the kneaded product into a pellet. In the case of cylindrical or rectangular batteries, the positive electrode can be obtained by adding the above additives and, in addition, organic solvents, such as N-methylpyrrolidone, to the lithium manganate powders of the present invention, kneading them to prepare a paste , coating the paste on a metal current collector, such as an aluminum sheet, and drying the coating. As the electrolytes of the lithium battery, those preparations can be used by dissolving the lithium ion in a polar organic solvent, which is neither oxidized nor reduced to a potential in a wider range than the chemically stable range, i.e. Potential range in which the battery works as a lithium battery. Examples of polar organic solvents are propylene carbonate, ethylene carbonate, diethyl carbonate, dimethoxyethane, tetrahydrofuran, β-butyrolactone, and mixtures thereof. As a solute for the lithium ion source, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, and the like can be used. Also, a porous polypropylene film or a polyethylene film is placed as a separator between the electrodes. As examples of the batteries, mention may be made of the flat batteries in the form of coins, by arranging a separator between the positive electrode of the pellet type and a negative electrode, attaching them by pressure to a can sealed with a propylene gasket, emptying an electrolyte there, and sealing them, and a cylindrical battery, obtained by coating a positive electrode material and a negative electrode material on metal current collectors, rolling them with a separator between them, inserting them into a battery can with a gasket, emptying an electrolyte there and sealing the can. Also, there are batteries of three electrode type, which are used especially for the measurement of electrochemical characteristics. These batteries, in which a reference electrode is placed, in addition to the positive electrode and the negative electrode, evaluates the electrochemical characteristics of the respective electrodes, controlling the potential of the positive and negative electrodes with respect to the reference electrode. - - The performance of lithium manganese as the material of the positive electrode, can be evaluated by building a lithium battery in the aforementioned way, charging and discharging the battery to a suitable potential and current, and measuring the electrical capacity. Also, the characteristics of the cycle can be judged from the change in electrical capacity, caused by the repetition of the charge and the discharge. EXAMPLES Examples of the present invention are shown below, but this invention is never limited by these examples Example 1 Synthesis of manganese hydrate 815 g of manganese sulfate (86% by weight, such as MnSQ 4) were dissolved in water to prepare 6,179 liters of a solution This aqueous solution of manganese sulfate was charged into a 10 liter glass reaction vessel, and, with agitation, 2,321 liters of sodium hydroxide at a concentration of 4 mol / l were added. liter and dispersed in the aqueous solution for a period of 1 hour, in a nitrogen atmosphere, maintaining the temperature at 15 ± 5 ° C, to obtain the manganese hydroxide.

Synthesis of manganese oxide The resulting aqueous paste, containing the manganese hydroxide, was heated to 60 ° C and air was blown there for 1 hour, to oxidize the manganese hydroxide in an aqueous medium, followed by aging for 1 hour with the blowing of nitrogen gas, instead of air, and then filtering and washing with water. The resulting filter mass was dried at 110 ° C for 12 hours, to carry out the gas phase oxidation, to obtain the manganese oxide. This manganese oxide was of a large specific surface area and with a void content, and was composed mainly of 2MnO-Mn02. Synthesis of the lithium manganese precursor __ The resulting manganese oxide (240 g, in terms of Mn) was dispersed in water, to prepare an aqueous paste. Pure water and 0.920 liter of lithium hydroxide with a concentration of 3.206 mol / liter were added to the aqueous paste to obtain 2.40 liters of a liquid. This was charged into a 3 liter glass reaction vessel and heated to 80 ° C, and the reaction was carried out for 3 hours by blowing air there. The evaporated water was replenished and then a portion of the aqueous paste was taken and its alkaline concentration was measured, to find that 18.8% by weight of the added lithium reacted with the manganese oxide. This aqueous paste was charged in an autoclave and subjected to a hydrothermal treatment at 130 ° C for 2 hours. The aqueous paste was cooled to 80 ° C and then the alkali concentration in this aqueous paste was measured, in the same manner as before, to find that 57.1% by weight of the added lithium reacted with the manganese oxide. The air was blown into this aqueous paste for 2 hours, and this aqueous paste again underwent a hydrothermal treatment at 130 ° C for 2 hours, to obtain an aqueous paste of a lithium manganese precursor (sample a-) by a process of intermittent type. After the aqueous slurry was cooled to 80 ° C, the alkali concentration was measured in the same manner as before, to find that 74.1% by weight of the added lithium reacted with the manganese oxide. The molar ratio of Li to Mn in the sample was 0.50.

An X-ray diffraction pattern of the sample a is shown in Figure 1. From Figure 1 it is recognized that the lithium manganese precursor of sample a was a mixture comprising mainly a solids solution of 2MnO-Mn02 and Li20-MnO-Mn02, LiMn204, LiMn02, and the like.

Synthesis of lithium manganate Air was blown into the aqueous paste of the resulting precursor, for 2 hours, followed by filtration. The washing was not carried out. The filter mass was dried at 110 ° C and then calcined at 500 ° C for 3 hours in the air, to obtain a lithium manganese (sample A) of the present invention.

Example 2 Synthesis of manganese hydroxide Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide Manganese oxide was obtained in the same manner as in Example 1.

Synthesis of the lithium manganese precursor _ The resulting manganese oxide (240 g, in terms of Mn) was dispersed in water, to prepare an aqueous paste. Pure water and 0.870 liter of lithium hydroxide with a concentration of 3.206 mol / liter were added to the aqueous paste to obtain 2.40 liters of a liquid. This was charged into a 3 liter glass reaction vessel and heated to 80 ° C, and the reaction was carried out for 3 hours by blowing air there. The evaporated water was replenished and then a portion of the aqueous paste was taken and its alkaline concentration was measured, to find that 16.4% by weight of the added lithium reacted with the manganese oxide. This aqueous paste was charged in an autoclave and subjected to a hydrothermal treatment at 150 ° C for 2 hours. The aqueous paste was cooled to 80 ° C and then the alkali concentration in this aqueous paste was measured, in the same manner as before, to find that 61.1% by weight of the added lithium reacted with the manganese oxide. The air was blown into this aqueous paste for 2 hours, and this aqueous paste again underwent a hydrothermal treatment at 150 ° C for 2 hours, to obtain an aqueous paste of a lithium manganese precursor (sample b) by a process of intermittent type. After the slurry was cooled to 80 ° C, the alkali concentration was measured in the same manner as before, to find that 78.3% by weight of the added lithium reacted with the manganese oxide. The molar ratio of Li to Mn in the sample was 0.50.

Synthesis of lithium manganate Air was blown into the aqueous paste of the resulting precursor, for 2 hours, followed by filtration. The washing was not carried out. The filter mass was dried at 110 ° C and then calcined at 500 ° C for 3 hours in the air, to obtain a lithium manganate (sample B) of the present invention. Example 3 Synthesis of manganese hydroxide _ Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide Manganese oxide was obtained in the same manner as in Example 1.

Synthesis of the lithium manganese precursor The resulting manganese oxide (186.5 g, in terms of Mn) was dispersed in water, to prepare an aqueous paste. Pure water and 0.746 liter of lithium hydroxide with a concentration of 3,000 moles / liter were added to the aqueous past, to obtain 2.40 liters of a liquid. This was charged in a 3 liter glass reaction vessel heated to 80 ° C, and the reaction was carried out for 3 hours by blowing air there. The evaporated water was replenished and a portion of the aqueous paste was taken and measured at alkaline concentration, to find that 13.8% by weight of the added lithium reacted with the manganese oxide. This aqueous paste was charged in an autoclave and subjected to a hydrothermal treatment at 180 ° C for 2 hours. The aqueous pasture was cooled to 80 ° C and then the alkali concentration in this aqueous paste was measured in the same manner as before, to find that 55.5% by weight of the added lithium reacted with the manganese oxide. The air was blown into this aqueous paste for 2 hours, and this aqueous slurry was again subjected to a hydrothermal treatment at 180 ° C for 2 hours, to obtain an aqueous paste of a lithium manganese precursor (sample c) by a process of intermittent type. After the slurry was cooled to 80 ° C, the alkali concentration was measured in the same manner as before, to find that 79.1% by weight of the added lithium reacted with the manganese oxide. The molar ratio of Li to Mn in the sample was 0.52.

Synthesis of lithium manganate Air was blown into the aqueous paste of the resulting precursor, for 2 hours, followed by filtration. The washing was not carried out. The filter mass was dried at 110 ° C and then calcined at 500 ° C for 3 hours in the air, to obtain a lithium manganese '(sample C) of the present invention.

Example 4 Synthesis of Manganese Hydroxide Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide The resulting aqueous paste, containing manganese hydroxide, was heated to 60 ° C and air was blown there for 1 hour to oxidize the manganese hydroxide in an aqueous medium, followed by aging for 1 hour, with blowing of nitrogen gas, instead of air, and then it was filtered and washed with water. The resulting filter mass was dried at 200 ° C for 12 hours, to carry out the gas phase oxidation, to obtain the manganese oxide. This manganese oxide had a large surface area and void content, and was mainly composed of 2MnO-Mn02.

Synthesis of the lithium manganese precursor The resulting manganese oxide (186.5 g, in terms of Mn) was dispersed in water, to prepare an aqueous paste, pure water and 0.746 liter of lithium hydroxide with a concentration of 3,000 moles were added. / liter, to the aqueous paste, to obtain 2.40 liters of a liquid, which was charged in an autoclave and subjected to the hydrothermal treatment at 180 ° C for 2 hours.The aqueous paste was cooled to 80 ° C and then a part of the aqueous paste was taken and its alkaline concentration was measured, to find that 31.9% by weight of the added lithium reacted with the manganese oxide.Air was blown into this aqueous paste, for 2 hours, and which was again subjected to to a hydrothermal treatment at 180 ° C for 2 hours.The aqueous paste was cooled to 80 ° C and then the concentration of alkali in this aqueous paste was measured, in the same manner as before. to find that 56.6% by weight of the added lithium reacted with the manganese oxide. The air was blown into this aqueous paste for 2 hours, and this aqueous slurry was again subjected to a hydrothermal treatment at 180 ° C for 2 hours, to obtain an aqueous slurry of a lithium manganese precursor (sample d) by a process of intermittent type. After the aqueous paste was cooled to 80 ° C, the alkali concentration was measured in the same manner as before, to show that 75.8% by weight of the added lithium reacted with the manganese oxide. The molar ratio of Li to Mn in the sample was 0.50.

Synthesis of lithium manganate Air was blown into the aqueous paste of the resulting precursor, for 2 hours, followed by filtration. The washing was not carried out. The filter mass was dried at 50 ° C and a part of it was calcined at 500 ° C, 700 ° C or 800 ° C for 3 hours in the air, to obtain a lithium manganate (samples D, E and F ) of the present invention. Example 5 Synthesis of manganese hydroxide 1146 g of manganese chloride tetrahydrate (99% by weight, such as MnCl2-H20), were dissolved in water to prepare 7.153 liters of a solution. This aqueous solution of manganese chloride was charged to a 10 liter glass reaction vessel and, with stirring, 1847 liters of sodium hydroxide of 6.209 mol / liter concentration were added and dispersed in the aqueous solution over a period of 1 hour, in a nitrogen atmosphere, maintaining the temperature at 15 ± 5 ° C, to obtain the manganese hydroxide.

Synthesis of manganese oxide The resulting aqueous paste, containing the manganese hydroxide, was heated to 60 ° C and the air was blown there for 7 hours, to oxidize this manganese hydroxide in an aqueous medium, followed by filtration, washing with water and re-form a pulp, to obtain an aqueous paste of manganese oxide. This manganese oxide had a large specific surface area and a high void content and was composed mainly of 2MnO-Mn02.

Synthesis of the lithium manganese precursor To the resulting manganese oxide aqueous paste (186.5 g, in terms of Mn) was added water and 0.746 liter of lithium hydroxide of 3,000 moles / liter concentration, to obtain 2.40 liters of a liquid. This was charged in a 3 liter glass reaction vessel and heated to 80 ° C, and the reaction was carried out for. 3 hours, blowing air. The evaporated water was replaced and then a part of the aqueous paste was taken and its alkali concentration was measured, to find that 9.58% by weight of the added lithium reacted with the manganese oxide. The aqueous paste was cured in an autoclave and subjected to a hydrothermal treatment at 180 ° C for 2 hours. The slurry was cooled to 80 ° C and then a portion of the slurry was taken and the alkali concentration thereof was measured, to find that 64.6% by weight of the added lithium had reacted with the manganese oxide. The air was blown into this aqueous paste for 2 hours, and this fresh aqueous paste was subjected to a hydrothermal treatment at 180 ° C for 2 hours, to obtain an aqueous paste of a lithium manganese precursor (sample g_) by a process of intermittent type. After the aqueous slurry was cooled to 80 ° C, the alkali concentration was measured in the same manner as before, to find that 75.8% by weight of the added lithium was reacted with the manganese oxide. The molar ratio of Li to Mn in the sample was 0.50.

Synthesis of lithium manganate Air was blown into the aqueous paste of the resulting precursor, for 2 hours, followed by filtration. The washing was not carried out. The filter mass was dried at 50 ° C and a part thereof was calcined at 500 ° C, for 3 hours in the air, to obtain a lithium manganate (sample G) of the present invention.

Example 6 Synthesis of Manganese Hydroxide Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide Manganese oxide was obtained in the same manner as in Example 1.

Synthesis of the lithium manganese precursor 0.304 liter of lithium hydroxide of concentration of 3,000 moles / liter was added to the resulting manganese oxide (100 g in terms of Mn), followed by "mixing thoroughly with stirring, then the mixture was evaporated to dryness at 110 ° C, to obtain a precursor of lithium manganese (sample h).

Lithium Manganate Synthesis _ Sample h was finely milled using a medium size mill and then calcined at 750 ° C for 3 hours in air, to obtain a lithium manganese (sample H) of the present invention. ---- - _ -. Example 7 Synthesis of Manganese Hydroxide Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide Manganese oxide was obtained in the same manner as in Example 1.

Synthesis of the precursor lithium manganate The resulting manganese oxide (324 g, in terms of Mn) was dispersed in water, to prepare an aqueous paste. Pure water and 0.966 liter of a solution of lithium hydroxide with a concentration of 3.665 mol / liter were added to the slurry to obtain 2.40 liters of a liquid. This was loaded in a 3 liter glass reaction vessel, and the reaction was carried out for 13 hours, with heating at "90 ° C and with blowing 1 liter / minute of oxygen gas, to obtain a precursor of lithium manganate (sample 1) The evaporated water was replenished and then a part of the aqueous paste was taken and its alkali concentration was measured, to find that 89.4% by weight of the added lithium reacted with the manganese oxide. The molar ratio of Li to Mn in sample i was 0.54.

Synthesis of lithium manganate The aqueous paste of the resulting precursor was filtered. The washing was not carried out. The filter mass was dried at 110 ° C and then calcined at 750 ° C for 3 hours in the air, to obtain a lithium manganese (sample I) of the present invention.

Example 8 Synthesis of Manganese Hydroxide Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide The resulting aqueous paste, containing the manganese hydroxide, was heated to 60 ° C. This aqueous paste had a pH of 8.3. The manganese hydroxide was oxidized in the aqueous paste by blowing 2 liters / minute of oxygen gas into it, until the pH reached 6. Successively, with the blowing of the oxygen gas in the slurry, a hydroxide solution of sodium of 2 mol / liter of concentration, was added to adjust the pH in 9. followed by heating to 90 ° C, aging for 2 hours, maintaining the pH of 9, filtering and washing with water. The mass of the resulting filter was dispersed in pure water, to obtain an aqueous paste of 100 g / 1 concentration in terms of Mn. This aqueous paste had a pH of 10.7. With stirring, an aqueous solution of hydrochloric acid with a concentration of 1 mol / liter was added and dispersed in the aqueous paste at room temperature to adjust the pH to 6. Maintaining the pH at 6, the reaction was carried out at room temperature. After 3 hours, followed by filtration, washing with water and drying at 70 ° C for 15 hours in the air, to obtain a manganese oxide. This manganese oxide had a large specific surface area and a high void content and was composed mainly of 2MnO-Mn02.

Synthesis of the precursor lithium manganate The resulting manganese oxide (312 g, in terms of Mn) was dispersed in water, to prepare an aqueous paste. Pure water and 0.877 liter of a solution of lithium hydroxide with a concentration of 3-655 mol / liter were added to the aqueous paste, to obtain 2.40 liters of a liquid. This was charged in a 3 liter glass reaction vessel, and the reaction was carried out for 6 hours, with heating at 90 ° C and with blowing 1 liter / minute of oxygen gas, to obtain a manganate precursor of lithium (sample j_). The evaporated water was replenished and then a portion of the aqueous paste was taken and its alkali concentration was measured, to find that 89.8% by weight of the added lithium reacted with manganese oxide. The molar ratio of Li to Mn in sample j. it was 0.51.

Synthesis of lithium manganate The aqueous paste of the resulting precursor was filtered. The washing was not carried out. The filter mass was dried at 110 ° C and then calcined at 750 ° C for 3 hours in the air, to obtain a lithium manganese (sample J) of the present invention.

Example 9 Synthesis of manganese hydroxide __ 815 g of manganese sulfate (86% by weight, such as MnS04), were dissolved in water to prepare 6,179 liters of a solution. This aqueous solution of manganese sulfate was charged to a 10 liter glass reaction vessel and, with stirring, heated to 60 ° C under a nitrogen atmosphere. Maintaining at 60 ° C, 2,321 liters of sodium hydroxide of 4 mol / liter concentration were added and dispersed in the aqueous solution in a period of 1 hour, to obtain the manganese hydroxide. - Synthesis of manganese oxide The resulting aqueous paste, which contains manganese hydroxide, has a pH of 8.3. With blowing 2 liters / minute of oxygen gas into the slurry, the manganese hydroxide was oxidized in the slurry to a pH of 6, followed by filtration and washing with water. The resulting filter mass was dispersed in pure water7 to prepare an aqueous paste of 100 g / 1 in terms of Mn, which was charged into a 5 liter glass reaction vessel, and heated to 60 ° C. 1,329 liters of an aqueous solution of hydrochloric acid of 1 mol / liter of concentration, was added and dispersed in the aqueous paste, and then the reaction was carried out for 3 hours, to replace a part of the Mn2 * contained in the 2 Mn0-Mn02 produced with. protons, followed by filtration and washing with water. By the acid treatment, the color of the aqueous paste changed from a light brown to a blackish brown. This aqueous paste, after completing the reaction, had a pH of 4.6.

Synthesis of the lithium manganese precursor The resulting manganese oxide (312 g, in terms of Mn) is dispersed? in water to prepare an aqueous paste. To this aqueous paste was added pure water and 0.841 liter of a solution of lithium hydroxide of 3.655 moles / liter of concentration, to obtain 2.40 liters of a liquid. This was charged in a 3 liter glass reaction vessel, and the reaction was carried out for 1 hour, with heating at 90 ° C and with blowing of ~~ 1 liter / minute of oxygen gas. The evaporated water was replenished and then a portion of the aqueous pulp was taken and its alkali concentration was measured, to find that 55.6% by weight of the added lithium reacted with the manganese oxide. The aqueous paste was charged in an autoclave and subjected to a hydrothermal treatment at 130 ° C for 3 hours. The aqueous paste was cooled to 90 ° C and then the alkali concentration thereof was measured, in the same manner as before, to find that 76.9% by weight of the added lithium had reacted with the manganese oxide. By blowing 1 liter / minute of oxygen gas into this aqueous paste, the reaction was carried out at 90 ° C for 2 hours, to obtain a precursor of lithium manganese (sample k). In the same manner as before, the concentration of the aqueous paste was measured and it was found that 93.7% by weight of the added lithium reacted with the manganese oxide. The molar ratio of Li to Mn in sample k was 0.51.

Synthesis of lithium manganate The aqueous paste of the resulting precursor was filtered. The washing was not carried out. The filter mass was dried at 110 ° C and then calcined at 750 ° C, for 3 hours, in the air, to obtain a lithium manganese (sample K) of the present invention.

Comparative Example 1 Synthesis of lithium manganese 50 g of manganese dioxide, reactive grade (95% by weight as Mn02, manufactured by Kanto Kagaku Co., Ltd.) were mixed with lithium hydroxide monohydrate, with a molar ratio of Li / Mn of 0.505. The mixture was thoroughly mixed and ground by a small mill, and then loaded into an alumina crucible and calcined at 750 ° C for 3 hours in the air, to obtain a lithium manganese (sample L) from a comparative sample.

Comparative Example 2 Synthesis of Manganese Hydroxide Manganese hydroxide was obtained in the same manner as in Example 1.

Synthesis of manganese oxide. The manganese oxide was obtained in the same manner as in Example 1.

Synthesis of lithium manganate The resulting manganese oxide (50 g, in terms of Mn), was mixed with the lithium hydroxide monohydrate in a molar ratio of Li / Mn of 0.505. The mixture was thoroughly mixed and ground in a small mill, and then loaded in an alumina crucible and calcined at 750 ° C for 3 hours in the air, to obtain a lithium manganese (sample M) of a comparative sample. The properties of the comparative samples A-M were measured and shown in Table 1. It was confirmed by observation with an electron microscope that the particulate form of the lithium manganese of the "present" invention was cubic. (As examples, the electron scanning photomicrographs of samples A and C are presented in Figures 3 and 4.) The samples partially contained amorphous particles, but this amount of amorphous particles was slight. On the other hand, the comparative sample M contained partially cubic particles, but the proportion of amorphous particles in this sample was very high as in the comparative sample L.

Also, the lithium manganates of the present invention were recognized as excellent in crystallinity in view of the results "that were obtained by a diffraction pattern of the stain type, in the electronic diffraction (as an example, an electron diffraction sample A is shown in Figure 5), that the single-grid image was shown in the observation by the transmission-type electron microscope, ultra-high amplification (transmission electron micrograph of sample A is presented in Figure 5, as an example), and that the lithium manganates have a single composition of LiMn20, as a result of X-ray diffraction (X-ray diffraction pattern of the sample A is presented in Figure 2, as an example). In addition, the BELLSOAP-2 device was used to measure the specific surface area by the BET method and the void content by nitrogen adsorption. 8, manufactured by Japan Bell., CO. , Ltd., for the measurement of void content. The results of the measurements are shown in Table 1. It can be seen from Table 1 that samples A-K have a satisfactory specific surface area and have voids in the particles. Next, the loading and unloading characteristics and cycle characteristics of the secondary lithium batteries, which are used by the A-M samples, as active materials of the positive electrodes were evaluated. The batteries were triple-electrode cells, and charging and discharging was repeated. - The batteries and the measurement conditions will be explained. Each of the samples, a graphite powder, as a conductive agent, and a polytetrafluoroethylene resin, as a binder, were mixed in a ratio of 3: 2: 1, and the mixture was kneaded in an agate mortar. The kneaded product was molded in a circular shape of 14 mm in diameter, to obtain a pellet. The weight of the pelle fe of 50 mg. It was placed between meshes made of metallic titanium, followed by pressing under a pressure of 150 kg / cm2, to obtain a positive electrode. Separately, metallic lithium of 0.5 mm thickness was molded in a circular shape of 14 mm in diameter and placed between meshes made of metallic nickel, followed by press bonding to obtain a negative electrode. Also, a metallic lithium sheet of 0.1 mm thickness was wound around a metallic nickel wire, so that the lobe was of a size of a grain of rice / whereby a reference electrode was obtained. As a non-aqueous electrolyte, a mixed solution of 1,2-dimethoxyethane and propylene carbonate (1: 1) was used., in volume ratio) in which the lithium perchlorate was dissolved at a concentration of 1 mol / liter. The electrodes were placed in the order of the positive electrode, reference electrode and negative electrode, and a porous polypropylene film was placed between them, as a separator. The measurement of the charge and discharge cycle was carried out at a constant adjustment of the current and the voltage varies from 4.3 to 3.5 V and the charge and discharge current is 0.25 mA (approximately 1 cycle / day). The initial capacity of the discharge, that is to say the discharge capacity in the tenth cycle and the capacity retention regime at that moment, are shown in Table 1. The capacity was per 1 g of the active material of the positive electrode.

Table 1 Initial discharge capacity and characteristics of the battery cycle, which use lithium manganese as the active material of the positive electrode.

As shown in Table 1, the lithium manganese of the present invention showed a high initial discharge capacity of at least 95 mAh / g and furthermore, they provided excellent cycle characteristics. The lithium manganate, prepared by the conventional dry process, was apt to have defects in the crystalline structure, which causes the deterioration of the crystallinity, with the repetition of the loading and unloading, which results in the decrease of the capacity of the cycle. Also, lithium manganate is lower in the diffusion coefficient of the lithium ion, compared to lithium cobaltate, which has a layered rock salt structure, which has been practically used as the active material for the electrode positive secondary batteries lithium ion. On the other hand, the lithium manganate of the present invention has a cubic particle shape and contains voids in the particles, and thus is excellent in crystallinity. That is, it has advantageous conditions for the insertion of lithium and, thus, it is preferred to achieve the improvement of the current density.

INDUSTRIAL APPLICABILITY The lithium manganese of the present invention has a cubic particle shape and contains voids in the particles and, therefore, the lithium batteries that use it as a positive electrode material show a high initial discharge capacity and also They are excellent in the characteristics of the cycle. In addition, the production process of the present invention is a process according to which lithium manganese, which have the above characteristics, can be produced advantageously.

Claims (13)

1. A lithium manganese, which has a cubic form of particles and contains voids in these particles, provides an initial discharge capacity of at least 95 mAh / g, when used as an active material for the positive electrodes of lithium batteries.

2. A lithium manganese, according to claim 1, which has a specific surface area of 1 to 100 m2 / g.

3. A lithium manganese, according to claim 1, which has a particle diameter of 0.01 to 10 μm.

4. A process for producing a lithium manganate, which includes a step of reacting a d-manganese compound with an alkali, to obtain a manganese hydroxide, a step of oxidizing the hydroxide in an aqueous medium or a gas phase, to obtain a manganese oxide, a step of reacting the manganese oxide with a lithium compound, in an aqueous medium, to obtain a precursor of the lithium manganese, and a step of calcining this precursor with heating, to obtain a lithium manganese.

5. A process for producing a lithium manganate, which includes the step of reacting a manganese compound with an alkali, to obtain a manganese hydroxide, a step of oxidizing the hydroxide ~ in an aqueous medium or a gas phase, to obtain a manganese oxide, a step of reacting manganese oxide with an acid, in an aqueous medium, to substitute protons for a part of the manganese, to obtain a substituted manganese oxide in the protons, a stage of reacting the manganese oxide, substituted in the protons, with a lithium compound, in an aqueous medium, to obtain a precursor of the lithium manganate, and a step of calcining this precursor with heating, to obtain a lithium manganese.

6. A method, according to claim 5, in which the acid is at least one acid selected from hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid.

7. A process according to claims 4 or 5 in which the manganese compound is a water-soluble manganese compound, in the step of reacting a manganese compound with an alkali, to obtain a manganese hydroxide. ~~ ~~

8. A process according to claims 4 or 5 in which the manganese compound or the substituted manganese oxide in the protons and the lithium compound are subjected to the hydrothermal treatment, in an aqueous medium, in the step of reacting an oxide of manganese or a substituted manganese oxide in the protons, with a lithium compound, in an aqueous medium, to obtain a precursor of the lithium manganese.

9. A process, according to claims 4 or 5, wherein the lithium compound is lithium hydroxide.

10. A process according to claim 4 or 5 wherein an oxidizing agent is fed, intermittently or continuously, in the step of reacting a manganese oxide or a substituted manganese oxide in the protons, with a lithium compound , in an aqueous medium, to obtain a precursor of lithium manganese.

11. A process, according to claim 10, wherein the oxidizing agent is at least one agent selected from air, oxygen, ozone, aqueous hydrogen peroxide and peroxodisulfate.

12. A positive electrode, for lithium batteries, which uses the lithium manganese, according to claim 1, as an active material of the positive electrode. ---

13. A lithium battery, which uses the positive electrode of claim 12.