JP5544798B2 - Method for producing lithium manganate and manganese dioxide used therefor - Google Patents

Description

  The present invention relates to a method for producing a manganese composite oxide used for a positive electrode active material for a lithium secondary battery and the like, and manganese dioxide used therefor.

  At present, spinel-structure lithium manganate mainly containing manganese is widely studied as a material to replace the layered rock-salt type lithium cobaltate, which is mainly used as a positive electrode active material of a lithium ion secondary battery (LIB). Patent Document 1).

  The characteristics of lithium manganate are greatly influenced by the manganese oxide used as the raw material. So far, electrolytic manganese dioxide and its heat-treated product (Patent Document 1), manganese carbonate, manganese dioxide by chemical method, trimanganese tetroxide, etc. (Patent Documents 2 to 4) have been studied as manganese raw materials for lithium manganate. Among them, electrolytic manganese dioxide and its heat-treated products can be used as raw materials to obtain dense and high energy density lithium manganate, and are suitable for resources, safety, and mass production. Therefore, it has high potential as a raw material for lithium manganate.

  When electrolytic manganese dioxide is used as a raw material for lithium manganate, it is necessary not to contain impurities, particularly sulfur components. However, since electrolytic manganese dioxide is usually produced by electrolytic deposition in a manganese sulfate bath, the amount of impurities after electrolytic deposition, particularly the sulfur component, is very high, and it was necessary to reduce it.

As a method for producing electrolytic manganese dioxide having a low sulfate radical (sulfur), the above-mentioned Patent Document 1 discloses a method of performing heat treatment after electrolysis with a high electric density of 130 A / m ² or more (Patent Document 1). However, lithium manganate using such electrolytic manganese dioxide as a raw material has a low capacity retention rate.

  A method of treating electrolytic manganese dioxide at a high temperature for 10 hours or more before mixing with a lithium compound is disclosed (Patent Document 5). However, after a short cycle (15 cycles), the charge / discharge cycle characteristics were already lowered.

  In addition, in the manufacturing method of lithium manganate, electrolytic manganese dioxide which is a manganese raw material is used after being pulverized and mixed and then granulated by spray drying or the like (Patent Document 6). Therefore, there is a demand for electrolytic manganese dioxide having a high BET specific surface area that can be easily pulverized and having few impurities.

  Thus, electrolytic manganese dioxide from which lithium manganate excellent in charge / discharge cycle characteristics is obtained has not been obtained.

Japanese Patent Laid-Open No. 06-150914 JP 2000-281347 A U.S. Pat. No. 2,956,860 JP 2004-292264 A Japanese Patent Laid-Open No. 11-157841 JP-A-10-172567

M.M. M.M. Thuckeray et al. , J. et al. Electrochem. Soc. , 139, 363 (1992)

  An object of the present invention is to provide electrolytic manganese dioxide suitable as a raw material for lithium manganate excellent in charge / discharge cycle characteristics of a secondary battery.

  As a result of intensive studies on electrolytic manganese dioxide used as a raw material for lithium manganate used as a positive electrode material of a secondary battery, the present inventors have obtained manganese obtained by using electrolytic manganese dioxide produced under specific electrolysis conditions. Lithium acid has been found to be remarkably excellent in charge / discharge cycle characteristics when used as a positive electrode material for a secondary battery, and has completed the present invention.

  Hereinafter, electrolytic manganese dioxide (hereinafter referred to as “electrolytic manganese dioxide”) used as a raw material for the lithium manganate of the present invention will be described.

Electrolytic manganese dioxide current density 0.6 A / dm ² to more than 1.1A / dm ² or less, preferably obtained by 0.9 A / dm ² or less of the electrolyte 0.8 A / dm ² or more. When the current density is 0.6 A / dm ² or less, the BET specific surface area decreases, and the lithium manganate using such electrolytic manganese dioxide has a low cycle maintenance rate when used as a positive electrode material for a secondary battery. It becomes. On the other hand, when the current density exceeds 1.1 A / dm ² , electrolytic manganese dioxide having a remarkably large BET specific surface area is obtained, and only lithium manganate having a low cycle retention rate can be obtained. Furthermore, when the current density exceeds 1.1 A / dm ² , the durability of the electrode base material in electrolysis deteriorates and stable electrodeposition is not possible.

The Mn ²⁺ / H ₂ SO ₄ weight ratio of the electrolytic solution composition is 1.0 or more and 4.0 or less, and preferably 1.5 or more and 2.2 or less. When the weight ratio of Mn ²⁺ / H ₂ SO ₄ is less than 1.0, the BET specific surface area decreases, and the sulfur concentration of electrolytic manganese dioxide increases. On the other hand, when it exceeds 4.0, manganese dioxide is not electrolytically deposited.

The weight ratio of Mn ²⁺ / H ₂ SO ₄ in the electrolytic solution is a value determined by the following formula.

_{C Mn = (C 'F-} Mn /0.90-C' H2SO4) × 54.94
C _H2SO4 = C ′ _H2SO4 × 98.02
Mn ²⁺ / _H 2 SO ₄ weight ratio _{= C Mn /} C _H2SO4
here,
C ′ _F—Mn : Mn concentration in replenisher (mol / L)
C _Mn : Mn concentration in electrolyte (g / L)
C ′ _Mn : Mn concentration in the electrolyte (mol / L)
C _H2SO4 : H ₂ SO ₄ concentration in the electrolyte (g / L)
C _{'H2SO4: H} 2 SO ₄ concentration in the electrolyte (mol / L)
It is.

The sulfuric acid concentration in the electrolytic solution is not particularly limited as long as the above Mn ²⁺ / H ₂ SO ₄ weight ratio is satisfied, but it can be exemplified as 20 to 50 g / L from the start to the end of electrolysis. In this case, the sulfuric acid concentration in the electrolytic solution throughout the electrolysis period may be constant or may be changed. In addition, the sulfuric acid concentration here excludes the divalent anion of manganese sulfate.

The manganese concentration of the electrolyte replenishing solution in the electrolyte is not particularly limited if ^Mn 2+ _/ H 2 SO ₄ weight ratio of above met, for example, can be exemplified by 30 to 60 g / L.

  The electrolysis temperature is preferably 97 ° C. or lower, particularly preferably 93 ° C. or lower. When electrolysis temperature exceeds 97 degreeC, the BET specific surface area of the obtained electrolytic manganese dioxide tends to become extremely large.

  After electrolysis, the obtained electrolytic manganese dioxide is pulverized and used. The pulverization method is not limited as long as the desired particle size can be obtained, and jaw crusher, mill pulverization or the like can be used.

  The electrolytic manganese dioxide after washing is preferably neutralized with an aqueous solution not containing an alkali metal such as sodium or potassium. Thereby, mixing of impurities derived from corrosion of metal equipment used in the manufacturing process can be prevented. Moreover, when neutralizing with the aqueous solution containing an alkali metal, these become easy to be taken in into electrolytic manganese dioxide as an impurity. As an aqueous solution not containing an alkali metal, for example, aqueous ammonia is preferably used.

  As for the drying temperature of electrolytic manganese dioxide, the temperature of 70-90 degreeC can be illustrated, for example.

  The electrolytic manganese dioxide is preferably classified as necessary to adjust the particle size.

Electrolytic manganese dioxide has a sulfur concentration of 2000 ppm to 3500 ppm, a sodium concentration of 100 ppm to 500 ppm, and a BET specific surface area of 30 m ² / g to 60 m ² / g.

  The sulfur concentration of electrolytic manganese dioxide is preferably 2000 ppm or more and 3500 ppm or less, and particularly preferably 2500 ppm or more and 3500 ppm or less. When the sulfur concentration exceeds 3500 ppm, it is difficult to remove sulfur from manganese dioxide before mixing with the lithium compound, and charge / discharge cycle characteristics of the resulting lithium manganate are lowered.

  The sodium concentration of electrolytic manganese dioxide is 100 ppm to 500 ppm, preferably 100 ppm to 400 ppm, and more preferably 150 ppm to 350 ppm. When the sodium concentration exceeds 500 ppm, it is difficult to remove sodium by electrolytic manganese dioxide alone before mixing with the lithium compound, and the charge / discharge cycle characteristics of the obtained lithium manganate are lowered.

The BET specific surface area of electrolytic manganese dioxide is preferably 30 m ² / g or more and 60 m ² / g or less, and particularly preferably 35 m ² / g or more and 58 m ² / g or less. Electrolytic manganese dioxide having a BET specific surface area in this range has a low hardness, is easy to grind, and avoids contamination by impurities.

  The purity of electrolytic manganese dioxide (especially sulfur derived from sulfate radicals) and the BET specific surface area mainly depend on the electrolysis conditions. Moreover, even if the electrolytic manganese dioxide has a similar BET specific surface area, if the sulfur concentration and sodium concentration of the present invention are different, lithium manganate using the same (the influence of other factors such as different metal doping) If not, the charge / discharge cycle characteristics obtained in the present invention cannot be obtained. That is, whether or not the raw material of lithium manganate satisfies the physical properties of the present invention can be determined by the charge / discharge cycle characteristics of lithium manganate.

  The average particle diameter of electrolytic manganese dioxide is preferably 1 μm to 35 μm, and particularly preferably 1 μm to 30 μm. If the average particle size is less than 1 μm, secondary aggregation of electrolytic manganese dioxide becomes obvious, and it becomes difficult to control the particle size of lithium manganate. On the other hand, when the particle size exceeds 35 μm, the particle size of the obtained lithium manganate tends to be larger than the thickness of the positive electrode active material layer.

  Electrolytic manganese dioxide is preferably used after being pulverized. Thereby, lithium manganate with a high density and a high capacity retention rate can be obtained.

Although electrolytic manganese dioxide can be used as it is as a raw material for lithium manganate, it can also be used after appropriately heat-treated. The heating temperature may be 200 ° C to 800 ° C. The heating time does not require long-time heating and can be exemplified by 1 to 5 hours, for example. Further, all or part of the electrolytic manganese dioxide can be used as Mn ₂ O ₃ or Mn ₃ O ₄ by heat treatment.

  The lithium compound to be reacted with electrolytic manganese dioxide is not particularly limited, and examples thereof include lithium hydroxide, lithium carbonate, and lithium nitrate.

  The mixing method before reacting the electrolytic manganese dioxide and the lithium compound is not limited as long as the two can be mixed uniformly, but the method of simply mixing the electrolytic manganese dioxide and the lithium compound, or mixing the electrolytic manganese dioxide and the lithium compound An example is granulation by spray drying.

  Electrolytic manganese dioxide and a lithium compound produce lithium manganate by firing. As firing conditions, general conditions can be applied, for example, firing at 700 to 1000 ° C. in an aerobic atmosphere.

  As long as the characteristics of the present invention are not impaired, a metal compound such as nickel, cobalt, and aluminum may be added together with the electrolytic manganese dioxide and the lithium compound.

  The lithium manganate obtained by the method of the present invention preferably has a crystallite size of 300 mm or more, particularly preferably 310 mm or more. Excellent charge / discharge cycle characteristics can be achieved when the crystal is a sufficiently grown lithium manganate.

  The lithium manganate using the electrolytic manganese dioxide of the present invention as a raw material can be used as a positive electrode active material for a secondary battery such as a lithium ion secondary battery.

  When constituting a secondary battery, other constituent elements are not limited, and commonly used negative electrode active materials, electrolytes, separators, and the like can be used. Examples of the negative electrode active materials include metallic lithium and lithium. Metals that can occlude and release ions or lithium ions, such as metallic lithium, lithium / aluminum alloys, lithium / tin alloys, lithium / lead alloys, and carbon materials that can electrochemically insert and desorb lithium ions, etc. Electrolytes such as carbonates, sulfolanes, lactones, and ether condyles in which lithium salts are dissolved, lithium ion conductive solid electrolytes, etc., and separators are microporous membranes made of polyethylene or polypropylene Etc. can be used.

  It has excellent charge and discharge cycle characteristics by using lithium manganate made from the electrolytic manganese dioxide of the present invention as a positive electrode active material, and has a high capacity maintenance rate of 98.0% or more according to the evaluation method described later. A secondary battery having discharge cycle characteristics can be configured.

  When the lithium manganate obtained by the method of the present invention is used as a positive electrode material of a secondary battery, it becomes a lithium ion secondary battery having high charge / discharge cycle characteristics.

It is a figure which shows the relationship between the BET specific surface area of electrolytic manganese dioxide, and impurity concentration. It is a figure which shows the relationship between the impurity concentration of electrolytic manganese dioxide, and the crystallite diameter of lithium manganate. It is a figure which shows the relationship between the impurity concentration of electrolytic manganese dioxide, and a capacity | capacitance maintenance factor (charging / discharging cycling characteristics).

  Next, although this invention is demonstrated with a specific Example, this invention is not limited to these Examples.

(Average particle size)
Electrolytic manganese dioxide or 0.5 g of lithium manganate is put into 50 mL of pure water, and a dispersion slurry prepared by ultrasonic irradiation for 10 seconds is put into a microtrack HRA (manufactured by HONEWELL). Distribution was measured and the average particle size was determined.

(Measurement of crystal phase)
Electrolytic manganese dioxide and lithium manganate were measured using a general X-ray diffractometer (MXP-3 manufactured by Mac Science). A CuKα ray (λ = 1.5405 mm) is used as the radiation source, the measurement mode is step scan, the scan condition is 0.04 ° per second, the measurement time is 3 seconds, and the measurement range is 2 ° to 5 ° to 80 °. Measured with

(BET specific surface area)
The BET specific surface areas of electrolytic manganese dioxide and lithium manganate were measured by nitrogen adsorption by the BET one-point method. In addition, the sample used for the measurement of the BET specific surface area was deaerated by heating at 150 ° C. for 40 minutes prior to the measurement of the BET specific surface area.

(Measurement of chemical composition)
The chemical composition of electrolytic manganese dioxide and lithium manganate was measured using ICP emission analysis.

(Measurement of tap density)
In order to examine the powder density of lithium manganate, 30 g of lithium manganate was filled in a 100 ml graduated cylinder and tapped 200 times. The filling volume after tapping was read, and the tap density was calculated from this volume and the weight of the filled lithium manganate.

(Measurement of capacity maintenance rate)
The battery characteristic test was performed by the method shown below. A mixture of lithium manganate, polytetrafluoroethylene as a conductive agent, and acetylene black (trade name: TAB-2) is mixed at a weight ratio of 4: 1 and meshed at a pressure of 1 ton / cm ² (manufactured by SUS316). ) After being molded into a pellet shape on top, it was dried under reduced pressure at 200 ° C. to produce a battery positive electrode.

Electrolysis in which lithium hexafluorophosphate was dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / dm ^{3 in} the obtained positive electrode for a battery, a negative electrode comprising a metal lithium foil (thickness 0.2 mm), and A battery was constructed using the liquid. Using the produced battery, the battery voltage was charged and discharged 50 times at 0.4 mA / cm ² at room temperature between 4.2 V and 3.0 V at a constant current. The discharge capacities (mAh / g) at the 10th and 50th times were Q ₁₀ and Q ₅₀ , respectively, and the ratio of these ratios was 100 × Q ₅₀ / Q ₁₀ (%) was the capacity retention rate.

Example 1
Electrolysis was performed for 10 days so that the current density was 0.83 A / dm ² , the electrolysis temperature was 93 ° C., and the electrolytic replenisher was a manganese sulfate solution having a manganese concentration of 47 g / l, and the sulfuric acid concentration in the electrolyte solution was 20 g / l. The weight ratio of Mn ²⁺ / H ₂ SO ₄ in the electrolytic solution was 2.1.

  The electrolytically deposited electrolytic manganese dioxide lump was pulverized by jet mill, then stirred and washed with hot water at 70 ° C. for 1 hour, and then neutralized with 10 wt% aqueous ammonia. The weight ratio of electrolytic manganese dioxide / warm water at this time was 1/10. After sufficiently drying at 80 ° C., air classification was performed to produce electrolytic manganese dioxide having an average particle size of 10 μm.

The obtained electrolytic manganese dioxide had a crystal phase of γ-type manganese dioxide, a BET specific surface area of 50 m ² / g, a chemical composition of 62 wt% manganese, 2600 ppm sulfur, and 290 ppm sodium.

  The electrolytic manganese dioxide and lithium carbonate having an average particle size of 3.5 μm were dry mixed and mixed so that the (lithium / manganese) molar ratio = 0.54. 100 g of the mixture was put in an alumina crucible and baked in an air muffle furnace at 900 ° C. for 1 day to produce lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite diameter was calculated by the Scherer method. The average particle size was 9.6 μm, and the capacity retention rate was 98.4%.

Example 2
Electrolysis was performed for 17 days so that the current density was 0.61 A / dm ² , the electrolysis temperature was 97 ° C., the electrolytic replenisher was a manganese sulfate solution having a manganese concentration of 47 g / l, and the sulfuric acid concentration in the electrolyte solution was 32 g / l. The weight ratio of Mn ²⁺ / H ₂ SO ₄ in the electrolytic solution was 1.1.

  The electrolytically deposited manganese dioxide mass was treated in the same manner as in Example 1 to produce electrolytic manganese dioxide having an average particle size of 10 μm.

The crystal phase of the obtained electrolytic manganese dioxide was γ-type manganese dioxide. The BET specific surface area was 36 m ² / g, the chemical composition was manganese 60 wt%, sulfur 3400 ppm, and sodium 290 ppm.

  Next, it processed like Example 1 and manufactured lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite size was calculated by the Scherer method. The average particle size was 9.5 μm and the capacity retention rate was 98.1%.

Example 3
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the average particle diameter of electrolytic manganese dioxide was 3.5 μm during wind classification.

The crystal phase of the obtained electrolytic manganese dioxide was γ-type manganese dioxide. The BET specific surface area was 56 m ² / g, the chemical composition was manganese 60 wt%, sulfur 2300 ppm, sodium 150 ppm.

  Electrolytic manganese dioxide was treated in the same manner as in Example 1 to produce lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite diameter was calculated by the Scherer method. Moreover, the average particle diameter was 3.9 micrometers and the capacity | capacitance maintenance factor was 98.3%.

Example 4
Electrolytic manganese dioxide was produced in the same manner as in Example 1 except that the average particle diameter of electrolytic manganese dioxide was changed to 29 μm during wind classification.

The crystal phase of the obtained electrolytic manganese dioxide was γ-type manganese dioxide. The BET specific surface area was 50 m ² / g, the chemical composition was 62 wt% manganese, 2600 ppm sulfur, and 290 ppm sodium.

  Electrolytic manganese dioxide was treated in the same manner as in Example 1 to produce lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite size was calculated by the Scherer method. The average particle size was 29 μm and the capacity retention rate was 98.0%.

Reference Example Electrolytic manganese dioxide obtained by the same method as in Example 1 was heat-treated in a muffle furnace in air at 550 ° C. for 5 hours.

The crystal phase after the heat treatment was dimanganese trioxide (Mn ₂ O ₃ ), and the average particle size was not changed. The BET specific surface area was 35 m ² / g, the chemical composition was 68 wt% manganese, 2700 ppm sulfur, and 330 ppm sodium.

  Next, it processed like Example 1 and manufactured lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite diameter was calculated by the Scherer method. Further, the average particle size was 9.3 μm, and the capacity retention rate was 98.5%.

Comparative Example 1
Electrolysis was carried out for 10 days so that the current density was 0.50 A / dm ² , the electrolysis temperature was 97 ° C., the electrolytic replenisher was a manganese sulfate solution having a manganese concentration of 47 g / l, and the sulfuric acid concentration in the electrolyte solution was 39 g / l. The weight ratio of Mn ²⁺ / H ₂ SO ₄ in the electrolytic solution was 0.78.

  The electrolytically precipitated manganese dioxide lump was pulverized by jet milling, neutralized with 10 wt% ammonia water, and stirred and washed with warm water at 70 ° C. for 1 hour. The weight ratio of electrolytic manganese dioxide / warm water at this time was 1/10. After sufficiently drying at 80 ° C., air classification was performed to produce electrolytic manganese dioxide having an average particle size of 10 μm.

The crystal phase of the obtained electrolytic manganese dioxide was γ-type manganese dioxide. The BET specific surface area was 28 m ² / g, the chemical composition was 59 wt% manganese, 3900 ppm sulfur, and 380 ppm sodium.

  Electrolytic manganese dioxide was treated in the same manner as in Example 1 to produce lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite diameter was calculated by the Scherer method. The average particle size was 9.6 μm and the capacity retention rate was 97.2%.

Comparative Example 2
Electrolytic manganese dioxide was produced in the same manner as in Comparative Example 1 except that 10 wt% aqueous ammonia during neutralization was changed to a 10 wt% sodium hydroxide aqueous solution.

The obtained electrolytic manganese dioxide had an average particle size of 10 μm and a crystal phase of γ-type manganese dioxide. The BET specific surface area was 26 m ² / g, the chemical composition was 57 wt% manganese, 3600 ppm sulfur, and 3400 ppm sodium.

  Electrolytic manganese dioxide was treated in the same manner as in Example 1 to produce lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite diameter was calculated by the Scherer method. The average particle size was 9.3 μm and the capacity retention rate was 96.8%.

Comparative Example 3
Electrolytic manganese dioxide was produced in the same manner as in Comparative Example 1 except that 10 wt% aqueous ammonia in the neutralization treatment was changed to 1 wt% sodium hydroxide aqueous solution.

The obtained electrolytic manganese dioxide had an average particle diameter of 10 μm and the crystal phase was γ-type manganese dioxide. The BET specific surface area was 28 m ² / g, the chemical composition was 57 wt% manganese, 3600 ppm sulfur, and 590 ppm sodium.

  Electrolytic manganese dioxide was treated in the same manner as in Example 1 to produce lithium manganate.

  The obtained lithium manganate had a (lithium / manganese) molar ratio = 0.53. Moreover, the crystal phase is a single phase of spinel phase, and all diffraction peaks can be indexed with a spinel structure (space group: Fd3-m), and no peak derived from the byproduct phase was observed. The half width of the 400 main diffraction peak was measured, and the crystallite diameter was calculated by the Scherer method. The average particle size was 9.6 μm and the capacity retention rate was 96.9%.

  The results of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

  As is apparent from this table, the lithium secondary battery using lithium manganese manganate obtained from the electrolytic manganese dioxide of the present invention as a raw material has a high capacity retention rate and excellent charge / discharge cycle characteristics. .

  The electrolytic manganese dioxide of the present invention is an electrolytic manganese dioxide having a high BET specific surface area and suppressing sodium and sulfur concentrations, and a lithium ion secondary battery having high charge / discharge cycle characteristics is produced using this electrolytic manganese dioxide as a raw material. It is possible.

Claims (4)

After mixing electrolytic manganese dioxide and a lithium compound having a sulfur concentration of 2000 ppm to 3500 ppm, a sodium concentration of 100 ppm to 500 ppm, and a BET specific surface area of 30 m ² / g to 60 m ² / g , 700 to 1000 in an aerobic atmosphere. The electrolytic manganese dioxide has a current density exceeding 0.6 A / dm ² and 1.1 A / dm ² or less, and the Mn ²⁺ / H ₂ SO ₄ weight ratio of the electrolytic solution composition is 1.0 or more and 4 A method for producing lithium manganate, characterized by electrolysis of 0.0 or less . 2. The method according to claim 1, wherein the crystallite diameter of lithium manganate is 300 mm or more. The manufacturing method according to claim 1 or 2 , wherein when the electrolytic manganese dioxide and the lithium compound are mixed, a cobalt or nickel compound is further mixed. Electrolytic manganese dioxide by electrolysis having a current density exceeding 0.6 A / dm ² and 1.1 A / dm ² or less, and a weight ratio of Mn ²⁺ / H ₂ SO _{4 of the} electrolytic solution composition of 1.0 or more and 4.0 or less, and sulfur Electrolytic manganese dioxide having a concentration of 2000 ppm to 3500 ppm, a sodium concentration of 100 ppm to 500 ppm, and a BET specific surface area of 30 m ² / g to 60 m ² / g.

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