JP5798606B2 - Method for producing lithium manganese phosphate positive electrode active material - Google Patents

Description

  The present invention relates to a method for producing a lithium manganese phosphate positive electrode active material for obtaining a lithium manganese phosphate positive electrode active material capable of expressing high battery properties.

  Conventionally, highly conductive substances have been used as positive electrode materials and negative electrode materials in order to improve battery performance. In recent years, next-generation batteries such as lithium ion batteries have been increasingly used, and various positive electrode materials for such batteries have been developed. Lithium manganese phosphate is one of them. Phosphoric acid, manganese compound and water are mixed to make an acidic solution, and lithium hydroxide is added dropwise to make it alkaline and subjected to hydrothermal reaction. An obtained method is known (see Non-Patent Document 1).

Under these circumstances, lithium manganese phosphate itself has low conductivity, and therefore, in order to effectively use it as a positive electrode active material, it is necessary to sufficiently refine the particles to ensure good battery properties. Various production methods are known for obtaining the substance. For example, in Patent Document 1, a solution containing lithium and a solution containing phosphorus are mixed, a weakly alkaline mixed solution is formed and dropped into a solution that can contain manganese or the like, and hydrothermal heat is generated using the obtained mixed solution. A method for producing a lithium-containing composite oxide by the method is disclosed. Patent Document 2 discloses that a precursor mixture containing a Li ⁺ source, a PO ₄ ³⁻ source, a manganese source, and the like is generated, and the obtained precursor mixture is subjected to dispersion or pulverization treatment under hydrothermal conditions. A method for obtaining a LiMPO ₄ compound by this reaction is disclosed.

JP 2012-211072 A JP 2007-511458 A

Hongmei Ji et al, Elestrochimica Acta 56 (2011), p3093-3100

  However, in any of the methods described in any of the above documents, the conditions to be selected for subjecting the prepared mixture or liquid mixture to a so-called hydrothermal reaction have not been sufficiently studied, and a high battery It has not yet reached lithium manganese phosphate that can express physical properties.

  Therefore, the subject of this invention is providing the manufacturing method for obtaining the lithium manganese phosphate positive electrode active material which can express the outstanding battery physical property as a positive electrode material of a lithium ion battery.

  Therefore, the present inventors have made various studies, and in the production method including a step of subjecting a reaction mixture obtained by mixing a transition metal compound containing a manganese compound to a hydrothermal reaction, an elapsed time required under specific conditions. It has been found that a lithium manganese phosphate positive electrode active material capable of exhibiting excellent battery physical properties can be obtained when the value obtained by integrating the product of (minute) and the temperature (° C.) of the reaction mixture is not more than a specific value. The invention has been completed.

That is, the present invention provides a lithium manganese phosphate positive electrode active material comprising a step of mixing a transition metal compound containing at least a manganese compound, a lithium compound, and a phosphate compound, and subjecting the resulting reaction mixture to a hydrothermal reaction. A method,
In the step for hydrothermal reaction, the elapsed time from the start of the hydrothermal reaction when the temperature of the reaction mixture is in the range of 60 to 210 ° C. between the start and end of the hydrothermal reaction ( The product of the product of (min) and the temperature (° C.) of the reaction mixture provides a method for producing a lithium manganese phosphate positive electrode active material having a value of 16000 (min · ° C.) or less.
Moreover, this invention provides the lithium manganese phosphate positive electrode active material obtained by the said manufacturing method.

  According to the method for producing a lithium manganese phosphate positive electrode active material of the present invention, in the obtained lithium manganese phosphate positive electrode active material, the particles can be sufficiently miniaturized. If it uses, it becomes possible to implement | achieve the lithium ion battery in which the weight energy density was raised dramatically easily.

In Example 1 and Comparative Example 1, it is the graph which plotted the temperature of the reaction mixture at the time of attaching | subjecting a reaction mixture to hydrothermal reaction, and the time from the time of a hydrothermal reaction start to the end. In Example 2 and Comparative Example 2, it is the graph which plotted the temperature of the reaction mixture at the time of attaching | subjecting a reaction mixture to hydrothermal reaction, and the time from the time of a hydrothermal reaction start to the end.

Hereinafter, the present invention will be described in detail.
In the method for producing a lithium manganese phosphate positive electrode active material of the present invention, a transition metal compound containing at least a manganese compound, a lithium compound, and a phosphoric acid compound are mixed, and an obtained reaction mixture (hereinafter referred to as “reaction mixture (X)”). A manufacturing method including a step of subjecting to hydrothermal reaction,
In the step of subjecting to a hydrothermal reaction, when the temperature of the reaction mixture (X) is within the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction, from the start of the hydrothermal reaction. A value obtained by integrating the product of the elapsed time (min) and the temperature (° C.) of the reaction mixture (X) is 16000 (min · ° C.) or less.

  Examples of the transition metal (M) compound (M represents a transition metal containing at least manganese) used in the present invention include at least a manganese compound and a hydrate thereof. Such a manganese compound may be a divalent manganese compound, and examples thereof include manganese halide, manganese sulfate, manganese acetate, and hydrates thereof. These may be used alone or in combination of two or more. Especially, it is preferable to use manganese sulfate and its hydrate from a viewpoint of improving battery physical property.

  Examples of other transition metal (M) compounds include iron compounds. The iron compound may be a divalent iron compound or a hydrate thereof, for example, a halide such as iron halide; a sulfate such as iron sulfate; an organic acid salt such as iron oxalate or iron acetate As well as hydrates thereof. Of these, iron sulfate and hydrates thereof are preferably used from the viewpoint of improving battery physical properties.

  Examples of the lithium compound used in the present invention include lithium oxide and lithium hydroxide. Specific examples include lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium oxide, lithium oxalate, and lithium acetate. These may be used alone or in combination of two or more. Among these, lithium hydroxide is preferable from the viewpoint of improving battery physical properties.

Examples of the phosphoric acid compound used in the present invention include phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and the like. These may be used alone or in combination of two or more. Among these, phosphoric acid is preferable from the viewpoint of improving battery physical properties. Phosphoric acid is so-called orthophosphoric acid (H ₃ PO ₄ ) and is preferably used as an aqueous solution having a concentration of 70 to 90% by mass.

  The reaction mixture (X) is obtained by mixing the transition metal (M) compound, the lithium compound, and the phosphoric acid compound. When a manganese compound and an iron compound are used as the transition metal (M) compound, their molar ratio (manganese compound: iron compound) in the reaction mixture (X) is preferably 99: 1 to 51:49, and more Preferably it is 95: 5-70: 30, More preferably, it is 90: 10-80: 20. Moreover, in reaction mixture (X), it is preferable to contain 0.28-0.38 mol of phosphoric acid compounds with respect to 1 mol of lithium compounds, and it is more preferable to contain 0.30-0.36 mol, More preferably, the content is 0.32 to 0.34 mol.

  As a method for obtaining the reaction mixture (X) by mixing the transition metal (M) compound, the lithium compound, and the phosphoric acid compound, for example, as described in Journal of Power Source 196 ′ (2011), p6498-6501). The method can be used.

  Specifically, for example, after first mixing a lithium compound, a phosphoric acid compound, and water, a transition metal (M) compound is added and further mixed to prepare an aqueous dispersion as a reaction mixture (X). Next, the obtained aqueous dispersion is subjected to a hydrothermal reaction.

  Alternatively, a reaction slurry (X) may be obtained by adding a transition metal (M) compound using a precursor slurry obtained by going through the following steps (I) to (II). Specifically, such a precursor slurry liquid is prepared by stirring the slurry water while dropping phosphoric acid into slurry water containing an amount of lithium compound exceeding the solubility in water, thereby preparing a mixed slurry liquid having a pH of 9 to 11. After the obtaining step (I), the obtained mixed slurry solution is purged with nitrogen to complete the reaction with the mixed slurry solution (II).

  More specifically, for example, in the step (I), slurry water containing an amount of lithium compound exceeding the solubility in water (g number of lithium compound dissolved in 100 g of saturated aqueous solution) is used. In order to prepare such slurry water, water and an amount of lithium compound exceeding the solubility in water may be mixed. Such slurry water preferably contains 1.5 to 3.5 times the amount of lithium compound, and contains 2.2 to 3.3 times the amount of lithium compound, based on the solubility of the lithium compound in water. More preferably, it contains 2.5 to 3.2 times as much lithium compound. For example, when using lithium hydroxide as a lithium compound, it is preferable to contain 20-50 mass parts lithium hydroxide with respect to 100 mass parts of water, and it contains 25-48 mass parts lithium hydroxide. Is more preferable, and it is more preferable to contain 30 to 45 parts by mass of lithium hydroxide.

In step (I), the slurry water is stirred while dropping the phosphoric acid compound into the slurry water to obtain a mixed slurry liquid having a pH of 9 to 11. In this way, the precursor of the lithium manganese phosphate positive electrode active material (phosphorus) is obtained by adding the phosphoric acid compound dropwise to the slurry liquid that is in a saturated state but containing an excessive amount of the lithium compound, and stirring while adding little by little. It is possible to effectively suppress agglomeration of dispersed particles of trilithium acid (Li ₃ PO ₄ ) and to effectively refine the particles. The dropping rate of the phosphoric acid compound into the slurry water is preferably 15 to 50 mL / min, more preferably 20 to 45 mL / min, and further preferably 28 to 40 mL / min.

  The mixed slurry obtained in step (I) contains 115 to 155 parts by mass of phosphoric acid with respect to 100 parts by mass of lithium hydroxide when lithium hydroxide is used as the lithium compound and phosphoric acid is used as the phosphoric acid compound. It is preferable to contain, 123 to 147 parts by mass, more preferably 131 to 139 parts by mass.

  In the step (II), the mixed slurry liquid obtained in the above step (I) is purged with nitrogen to complete the reaction in the mixed slurry liquid to obtain a precursor slurry liquid. The pressure in the step (II) is preferably 0.1 to 0.2 MPa, more preferably 0.1 to 0.15 MPa. Moreover, the temperature of a mixed slurry liquid becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 20-60 degreeC. The reaction time is preferably 5 to 60 minutes, more preferably 15 to 45 minutes.

What is necessary is just to add the said transition metal (M) compound and obtain reaction mixture (X) using the precursor slurry liquid obtained by passing through the said process (I) and process (II). The total addition amount of these transition metal compounds is preferably 0.99 to 1.01 moles per mole of lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) contained in the precursor slurry liquid. And more preferably 0.995 to 1.005 mol.

  The lithium manganese phosphate positive electrode active material is obtained through a step of subjecting the obtained reaction mixture (X) to a hydrothermal reaction. In the present invention, the hydrothermal reaction when the temperature of the reaction mixture (X) is in the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction in the hydrothermal reaction. The value obtained by integrating the product of the elapsed time (min) from the start of the reaction and the temperature (° C.) of the reaction mixture (X) is 16000 (min · ° C.) or less. The value obtained by integrating the product of the elapsed time (minutes) from the start of the hydrothermal reaction and the temperature (° C.) of the reaction mixture (X) means that the temperature of the reaction mixture (X) is within the range of 60 to 210 ° C. The present inventors have found that the performance of the lithium manganese phosphate positive electrode active material obtained is an index of the temperature history when changing, and the performance of the obtained lithium manganese phosphate positive electrode active material greatly depends on the value of the index of the temperature history. Is. That is, simply controlling the temperature of the reaction mixture (X) and the temperature raising or cooling time is insufficient to enhance the performance of the resulting lithium manganese phosphate positive electrode active material. Thus, controlling the value obtained by integrating the product of the elapsed time (minutes) and the temperature (° C.) of the reaction mixture (X) under specific conditions improves the performance of the resulting lithium manganese phosphate positive electrode active material It is found that it is linked to.

  If the temperature of the reaction mixture (X) is in the range of 60 to 210 ° C., at least the hydrothermal reaction can be effectively advanced and completed. This is due to the idea that it is optimal for estimating the influence on the performance of the lithium manganese oxide positive electrode active material.

  When the temperature of the reaction mixture (X) is in the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction, the elapsed time (minutes) from the start of the hydrothermal reaction and the reaction mixture ( The value obtained by integrating the product of X) with the temperature (° C.) is preferably 10,000 to 16000 (min · ° C.), more preferably 11000 to 15500 (min · ° C.), from the viewpoint of developing higher battery properties. It is.

  It is preferable that the temperature is raised and cooled between the start and end of the hydrothermal reaction. Thereby, the temperature of the reaction mixture (X) is changed within the range of 60 to 210 ° C., and the hydrothermal reaction proceeds and completes well, while the elapsed time (min) and the temperature of the reaction mixture (X) (° C.). It becomes easy to make the product of and an appropriate value. The maximum temperature of the reaction mixture (X) from the start to the end of the hydrothermal reaction is preferably 130 to 210 ° C, more preferably 150 to 200 ° C. That is, it is desirable to raise the temperature of the reaction mixture (X) so that the maximum temperature is reached.

  Moreover, from the viewpoint of obtaining a lithium manganese phosphate positive electrode active material that can further improve battery physical properties, the rate of temperature rise is preferably 2 to 30 ° C./min, and more preferably 5 to 20 ° C./min.

  Next, it is preferable to perform cooling. By performing the cooling, the product of the elapsed time (minutes) and the temperature (° C.) of the reaction mixture (X) is set to a good value while the temperature of the reaction mixture (X) is reached to a suitable maximum temperature. It becomes easy. The minimum temperature of the reaction mixture (X) from the start to the end of the hydrothermal reaction is preferably 20 to 55 ° C, more preferably 30 to 50 ° C. The cooling rate is preferably 0.4 to 2.0 ° C./min, and more preferably 0.6 to 2.0 ° C./min.

  The time during which the temperature of the reaction mixture (X) is 60 to 210 ° C. from the start to the end of the hydrothermal reaction is the product of the elapsed time (minutes) and the temperature (° C.) of the reaction mixture (X). From the viewpoint of easily obtaining a desired value, it is preferably 170 to 290 minutes, and more preferably 180 to 250 minutes. In addition, during the period from the start to the end of the hydrothermal reaction, the time during which the temperature of the reaction mixture (X) is 80 to 210 ° C. is the elapsed time (min) and the temperature (° C.) of the reaction mixture (X). From the viewpoint of easily obtaining a desired value, it is preferably 70 to 200 minutes, and more preferably 80 to 190 minutes.

  Furthermore, during the period from the start to the end of the hydrothermal reaction, the time until the temperature of the reaction mixture (X) once reaches the maximum temperature and reaches the minimum temperature is 120 to 270 minutes. Preferably, it is 130 to 250 minutes.

  The hydrothermal reaction is preferably performed in a pressure vessel. For example, the pressure when the reaction is performed at 130 to 200 ° C is preferably 0.3 to 1.5 MPa, and the reaction is performed at 140 to 180 ° C. The pressure is preferably 0.4 to 1.0 MPa. From the viewpoint of effectively preventing the oxidation of the transition metal (M) compound, it is preferable to use a steam heating autoclave. When the saturated steam is introduced into the autoclave and heating is started, it is preferable to further reduce the oxygen remaining in the autoclave by performing an operation to push out (replace) the air in the autoclave with the saturated steam.

  After completion of the hydrothermal reaction, the produced lithium manganese phosphate is preferably collected by filtration and washed. Washing is preferably performed with water using a filtration device having a cake washing function. The obtained crystals are dried if necessary. Examples of the drying means include spray drying, vacuum drying, freeze drying and the like. By this production method, the lithium manganese phosphate positive electrode active material can be obtained as particles.

  Furthermore, carbon may be supported on the particle surface of the obtained lithium manganese phosphate positive electrode active material using conductive carbon. Such conductive carbon is preferably carbon black, and specific examples thereof include acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Of these, acetylene black and ketjen black are preferred from the viewpoint of imparting good conductivity. In addition, as the shape of these conductive carbons, those having a hollow shape or voids are included from the viewpoint of favorably supporting carbon on the particle surface of the lithium iron manganese lithium positive electrode active material to express higher battery properties. It preferably has a shape. You may bake when carrying | supporting carbon. The firing conditions are 400 ° C. or higher, preferably 400 to 800 ° C. for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours under an inert gas atmosphere or reducing conditions.

The lithium manganese phosphate positive electrode active material obtained by the production method of the present invention is a particle having a sufficient surface area capable of expressing high battery properties. For example, the BET surface area of the lithium manganese phosphate positive electrode active material obtained by the production method of the present invention is preferably 21 to 50 m ² / g, more preferably 22 to 50 m ² / g.

  A method for producing a lithium ion battery using the thus obtained lithium iron manganese phosphate positive electrode active material of the present invention is not particularly limited, and any known method can be used. For example, such a lithium iron manganese phosphate positive electrode active material is mixed with additives such as a binder and a solvent to obtain a coating solution. At this time, if necessary, a conductive additive may be further added and mixed. The binder is not particularly limited, and any known agent can be used. Specific examples include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, and ethylene propylene diene polymer. Moreover, it does not specifically limit as this conductive support agent, Any well-known agent can be used. Specific examples include acetylene black, ketjen black, natural graphite, artificial graphite, and fibrous carbon. Next, such a coating solution is applied onto a positive electrode current collector such as an aluminum foil and dried to obtain a positive electrode.

  Here, as long as lithium ions can be occluded at the time of charging and released at the time of discharging, the material structure is not particularly limited, and a known material structure can be used. For example, a carbon material such as lithium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium, particularly a carbon material.

  The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones An oxolane compound or the like can be used.

The type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ ) ₂ and LiN (SO ₃ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and organic salt derivatives It is preferable that it is at least 1 sort of.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
<< Manufacture of lithium manganese phosphate cathode active material >>
4.9 kg of LiOH · H ₂ O and 11.7 kg of water were mixed to obtain slurry water. Subsequently, the obtained slurry water was stirred at a stirring speed of 400 rpm while maintaining the temperature at 25 ° C., and then 5.09 kg of a 70% phosphoric acid aqueous solution was dropped at 35 mL / min to obtain a mixed slurry liquid. . Next, the obtained slurry mixture was purged with nitrogen while stirring at a speed of 400 rpm for 30 minutes to complete the reaction with the slurry mixture, and the precursor adjusted to a dissolved oxygen concentration of 0.5 mg / L. A body slurry liquid was obtained.
Next, the precursor slurry was put into a synthesis vessel installed in a steam heating autoclave to start a hydrothermal reaction. The inside of the autoclave was heated at 170 ° C. for 1 hour using saturated steam obtained by heating water with a dissolved oxygen concentration of less than 0.5 mg / L by a diaphragm separator, and then the autoclave was rapidly cooled with cooling water. The stirring of the mixed slurry in the container was continued during the heating, and the hydrothermal reaction was terminated. The elapsed time (minutes) from the start of the hydrothermal reaction and the temperature of the reaction mixture when the temperature of the reaction mixture was in the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction. The value obtained by integrating the product with (° C.) was 14921 (min · ° C.).
The formed crystals were filtered and then washed with water. The washed crystal was vacuum-dried under conditions of 60 ° C. × 1 Torr to obtain lithium manganese phosphate primary particles as a powder. 10 g of the obtained lithium manganese phosphate primary particles and 2.7 g of glucose were mixed and put into a container provided in a planetary ball mill (P-5, manufactured by Fritsch), and 90 g of ethanol and 10 g of water were mixed therewith. The solvent obtained was added. Next, 100 g of balls having a spherical diameter (1 mm) were used and mixed for 1 hour at a rotational speed of 400 rpm. The obtained mixture was filtered, the solvent was distilled off using an evaporator, and then calcined at 600 ° C. for 1 hr in a reducing atmosphere to obtain a lithium manganese phosphate positive electrode active material.
BET surface area of the obtained lithium manganese phosphate positive electrode active material _{(Li Fe 0.15 Mn 0.85 PO 4} ) was measured in the Shimadzu Corporation DesorbIII, was 24m ² / g.

<Manufacture of lithium ion batteries>
The obtained lithium manganese phosphate positive electrode active material, ketjen black (conducting agent), and polyvinylidene fluoride (binding agent) were mixed at a weight ratio of 75: 20: 5, and this was mixed with N-methyl-2- Pyrrolidone was added and sufficiently kneaded to prepare a positive electrode slurry. The positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.

Next, a coin-type lithium ion battery was constructed using the positive electrode. A lithium foil punched to φ15 mm was used for the negative electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 was used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and housed in a conventional manner in an atmosphere having a dew point of −50 ° C. or lower to produce a coin type lithium ion battery (CR-2032).

  A charge / discharge test at a constant current density was performed using the manufactured lithium ion battery. The charging conditions at this time were constant current and constant voltage charging with a current of 0.1 CA (17 mAg) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 2.0 V. All temperatures were 30 ° C. The weight energy density (Wh / g) calculated based on the discharge capacity and the average discharge voltage was 606 Wh / g.

[Example 2]
A precursor slurry liquid was prepared in the same manner as in Example 1 except that 4.31 kg of Li ₂ CO ₃ was used instead of 4.9 kg of LiOH.H ₂ O, and water was prepared in the same manner as in Example 1 using this. The thermal reaction was started and terminated to produce a lithium manganese phosphate positive electrode active material. The elapsed time (minutes) from the start of the hydrothermal reaction and the temperature of the reaction mixture when the temperature of the reaction mixture was in the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction. The value obtained by integrating the product with (° C.) was 12441 (min · ° C.).
When the BET surface area of the obtained lithium manganese phosphate positive electrode active material ( Li 2 Fe _0.15 Mn _0.85 PO ₄ ) was measured in the same manner as in Example 1, it was 22 m ² / g. Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / g) was calculated in the same manner. It was 580 Wh / g.

[Comparative Example 1]
<< Manufacture of lithium manganese phosphate cathode active material >>
After heating at 170 ° C. for 1 hour in an autoclave, a precursor slurry liquid was prepared in the same manner as in Example 1 except that no rapid cooling with cooling water was performed, and a hydrothermal reaction was performed in the same manner as in Example 1 using this. The lithium manganese phosphate positive electrode active material was manufactured. The elapsed time (minutes) from the start of the hydrothermal reaction and the temperature of the reaction mixture when the temperature of the reaction mixture was in the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction. The value obtained by integrating the product with (° C.) was 18410 (min · ° C.).
BET surface area of the obtained lithium manganese phosphate positive electrode active material _{(Li Fe 0.15 Mn 0.85 PO 4} ) , measured in the same manner as in Example 1, was 20 m ² / g.

<Manufacture of lithium ion batteries>
Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / g) was calculated in the same manner. It was 575 Wh / g.

[Comparative Example 2]
After heating at 170 ° C. for 1 hour in an autoclave, a precursor slurry liquid was prepared in the same manner as in Example 2 except that the quenching with cooling water was not performed. The lithium manganese phosphate positive electrode active material was manufactured. The elapsed time (minutes) from the start of the hydrothermal reaction and the temperature of the reaction mixture when the temperature of the reaction mixture was in the range of 60 to 210 ° C. from the start to the end of the hydrothermal reaction. The value obtained by integrating the product with (° C.) was 18323 (min · ° C.).
The BET surface area of the obtained lithium manganese phosphate positive electrode active material ( Li 2 Fe _0.15 Mn _0.85 PO ₄ ) was 18 m ² / g as measured in the same manner as in Example 1. Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / g) was calculated in the same manner. It was 522 Wh / g.

Claims (2)

Phosphorus including a step of mixing a transition metal compound containing at least a manganese compound, a lithium compound, and a phosphate compound using a steam heating autoclave in which a synthesis vessel is installed, and subjecting the resulting reaction mixture to a hydrothermal reaction. A method for producing a lithium manganese oxide positive electrode active material,
In the process of hydrothermal reaction, from the start of the hydrothermal reaction, which is the time when the reaction mixture is charged into the synthesis container, to the end of the hydrothermal reaction, which is the time when the reaction mixture is removed from the synthesis container,
The pressure is 0.3 to 1.5 MPa,
The temperature is increased at a rate of 2 to 30 ° C / min, and the cooling is performed at a rate of 0.4 to 2.0 ° C / min.
When the temperature of the reaction mixture is in the range of 60 to 210 ° C., a value obtained by integrating the product of the elapsed time (min) from the start of the hydrothermal reaction and the temperature of the reaction mixture (° C.) is 16000 (min・ ℃) or less,
The time when the temperature of the reaction mixture is 60-210 ° C. is 170-290 minutes,
The manufacturing method of the lithium manganese phosphate positive electrode active material whose maximum temperature of the reaction mixture between the start time of hydrothermal reaction and the end time is 130-210 degreeC.   2. The manganese phosphate according to claim 1, wherein the time from when the temperature of the reaction mixture reaches the maximum temperature to the minimum temperature is 120 to 270 minutes from the start to the end of the hydrothermal reaction. A method for producing a lithium positive electrode active material.

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