JP4870602B2 - Method for producing lithium manganate - Google Patents

Description

  The present invention relates to a method for producing lithium manganate using manganese oxide and a lithium compound as raw materials, and lithium manganate obtained by the production method, and in particular, manganese that can be suitably used as a positive electrode active material for a lithium battery. The present invention relates to a method for producing lithium acid.

Nonaqueous electrolyte secondary batteries are characterized by a higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries, and are widely used as power sources for electronic devices. As the positive electrode active material of this non-aqueous electrolyte secondary battery, lithium transition metal composite oxides typified by LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and the} like are used.

Among them, LiMn ₂ O ₄ and LiMn ₂ O ₄ in which part of Mn is substituted with another metal (hereinafter also referred to as lithium manganate) has a large amount of constituent element manganese as a resource, It has the advantage that raw materials are easily available at low cost and have a low environmental impact. In order to take advantage of this advantage, nonaqueous electrolyte secondary batteries using lithium manganate have been used for mobile electronic devices such as mobile phones, notebook computers, digital cameras and the like.

  In recent years, mobile electronic devices have become more demanding due to high functionality such as various functions added and use at high and low temperatures. In addition, application to power sources such as batteries for electric vehicles is expected, and a battery capable of high-output and high-speed discharge that can follow sudden acceleration and rapid acceleration of an automobile is desired.

  For this reason, attempts have been made to refine the primary particle diameter of lithium manganate and improve the smooth insertion / extraction ability of Li.

  For example, in Patent Document 1 below, manganese oxide having an average primary particle diameter of 0.01 to 0.2 μm is mixed and fired with a lithium compound or the like and then pulverized to have an average primary particle diameter of 0.01. A method for producing lithium manganate having an average secondary particle diameter of 0.2 to 100 μm (31 to 43 μm is obtained in Examples) is disclosed.

  Patent Document 2 discloses a technique of pulverizing and atomizing lithium manganate or the like using a pulverization aid such as ethanol for the purpose of suppressing aggregation of the pulverized product. Is about 1 μm.

  Further, Patent Document 3 discloses a technique for producing a fine gel from a solution by a sol-gel method and firing it in order to refine the crystal diameter during the synthesis of lithium manganate.

JP 2002-104827 A JP 2003-048719 A Japanese Patent Laid-Open No. 10-247497

  However, none of the lithium manganate obtained by the prior art described above has been sufficiently enhanced.

  That is, in the production method of Patent Document 1, although manganese oxide having a small average primary particle size is used, it is described that pulverization after firing is performed to 100 μm or less (in the examples, the average secondary particle size is 30 μm or more), the average secondary particle size of the pulverized lithium manganate is increased. For this reason, it cannot be said that the insertion / extraction ability of Li is sufficient, and when used as a positive electrode active material, the charge / discharge performance in the battery becomes insufficient.

  In addition, in the production method disclosed in Patent Document 2, there is no description regarding the particle size of the raw material particles before firing, and after firing the raw material particles having a general particle size, pulverization with the addition of a grinding aid ( It has been found that the crystallinity of lithium manganate is reduced, particularly in high-speed discharge characteristics, in a state close to wet grinding.

  On the other hand, in the method of firing a fine gel produced from a solution as disclosed in Patent Document 3, it is difficult to control the primary particle diameter of lithium manganate produced by the crystallization reaction, and the average primary is increased by the growth of primary particles. The particle diameter increases, and smooth insertion / extraction of Li is less likely to occur.

  The problem to be solved by the present invention is to provide a method for producing lithium manganate, which is superior in high-speed discharge characteristics in a lithium battery, compared with conventional lithium manganate, and lithium manganate obtained by the production method. It is to be.

  The inventors of the present invention obtain lithium manganate that is particularly excellent in high-speed discharge performance by dry-grinding the fired product using manganese oxide having a specific average aggregate particle diameter to make the average aggregate particle diameter 10 μm or less. As a result, the present invention has been completed.

  That is, the method for producing lithium manganate of the present invention includes a firing step of firing in a state in which manganese oxide having an average aggregate particle size of 0.03 to 0.5 μm and at least a lithium compound are mixed, and the obtained firing And crushing to obtain lithium manganate having an average agglomerated particle size of 10 μm or less by dry pulverization of the product. In addition, the various physical-property values in this invention are values specifically measured by the method as described in an Example.

  According to the method for producing lithium manganate of the present invention, compared with conventional lithium manganate, a method for producing lithium manganate superior in high-speed discharge characteristics particularly in a lithium battery, and manganic acid obtained by the production method Lithium can be provided.

The lithium manganate obtained in the present invention (strictly refers to “lithium / manganese-containing metal composite oxide”) has a general formula of LiMn _2−x M _x O ₄ (where M is an element other than Mn (substitution element) X represents a constituent ratio (substitution ratio) of M in the composition formula), and may contain a substitution element other than Mn.

  The substitution element M is preferably an element that replaces Mn of lithium manganate and works as an effective element for suppressing elution of Mn into the electrolytic solution, and has an effect of improving battery performance and rate characteristics. Are Li, K, Ca, Mg, Ba, Fe, Ni, Zn, Co, Cr, Al, B, V, Si, Sn, P, Sb, Nb, Ta, Mo, and W, F, Ti, Cu At least one element selected from the group consisting of Zr, Pb, Ga, Sc, Sr, Y, In, La, Ce, Nd, S, and Bi is preferable. Of these, Mg, Al, Co, Fe, Cr, Ni, Zn, B and the like are particularly preferably used.

  The amount of M is 0 ≦ x ≦ 0.3, preferably x = 0 from the viewpoint of improving the initial charge / discharge characteristics, and 0 <x from the viewpoint of improving the repeated charge / discharge characteristics (cycle characteristics). ≦ 0.3 is preferred.

The crystalline phase of the obtained lithium manganate is preferably a spinel type. Specifically, the main peak obtained by X-ray diffraction measurement is JCPDS (Joint committee on powder diffraction standards): No. It may be the same as or equivalent to LiMn ₂ O ₄ shown in 35-782.

  In the present invention, primary particles are the smallest units that can be confirmed as particles when observed with an electron microscope. “Average primary particle diameter” refers to the number average particle diameter of primary particles observed with an electron microscope.

  Aggregated particles are aggregates of primary particles, and the average value of the particle sizes of these particles is referred to as the average aggregated particle size. A specific method for measuring the average aggregated particle size will be described later.

  The method for producing lithium manganate according to the present invention comprises manganese oxide (hereinafter referred to as “Mn source”) having an average aggregate particle size of 0.03 to 0.5 μm and at least a lithium compound (hereinafter referred to as “Li source”). It includes a firing step of firing in a mixed state.

  The firing step can be carried out, for example, by mixing a slurry obtained by wet pulverizing a Mn source with a solvent and a Li source, removing the solvent to form a solid, and then firing. The M component other than Mn may be added by dissolving a salt containing the M component in a solvent, or in the case of insolubility, it may be added during wet pulverization, or in the form of a solution or fine particles of 0.5 μm or less. Then, when adding the Li source, it may be added together.

  The average primary particle size of the lithium manganate of the present invention tends to be determined by the average aggregated particle size of the Mn source. That is, it is considered that the primary particle aggregates (aggregated particles) of the Mn source are sintered while taking in the Li source during the firing process, and change into primary particles of lithium manganate. Therefore, primary particles of lithium manganate to be generated can be controlled by controlling the average aggregated particle size of the Mn source by wet grinding or the like.

As the Mn source, one or more of MnO, Mn ₃ O ₄ , Mn ₂ O ₃ and MnO ₂ are preferably used. Among these, MnO ₂ and Mn ₂ O ₃ are particularly preferably used.

  The average primary particle size of the Mn source before pulverization is not particularly limited, but is preferably 0.01 μm to 0.5 μm from the viewpoint of ease of wet pulverization. In addition, the average aggregate particle size before pulverization is preferably 0.03 μm to 100 μm, and more preferably 0.03 μm to 50 μm, from the viewpoint of ease of wet pulverization.

  As the Li source, lithium compounds such as lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, lithium acetate, and lithium sulfate are preferable. Of these, lithium carbonate is preferable from the viewpoint of ease of primary particle control of lithium manganate. Used.

  The average primary particle size of the Li source before pulverization is not particularly limited, but is preferably 0.01 μm to 10 μm from the viewpoint of reactivity with the Mn source. Moreover, the average aggregate particle diameter before pulverization is preferably 0.03 μm to 100 μm, more preferably 0.03 μm to 50 μm, from the viewpoint of reactivity with the Mn source.

  In the present invention, the Mn source is controlled to an average aggregated particle size of 0.03 to 0.5 μm, but wet pulverization is preferably performed in the presence of a solvent. For the wet pulverization, a ball medium type mill such as a wet bead mill, a ball mill, an attritor or a vibration mill is preferably used. Moreover, when using Li source which is not melt | dissolved in a solvent, you may grind | pulverize a Li source separately with a Mn source separately.

The solvent used for the wet pulverization is preferably 100 ° C. or less, more preferably 90 ° C. or less, and still more preferably 80 ° C. or less from the viewpoint of removal by evaporation to dryness or spray drying after pulverization, from the viewpoint of ease of drying. . Specific examples of such a solvent include water, ethanol, acetone, methyl ethyl ketone, toluene, and tetrahydrofuran. Among these, a solvent that does not dissolve the Mn source is preferable from the viewpoint of precisely controlling the average aggregated particle size of the Mn source. For example, when the Mn source is MnO ₂ , preferred solvents are water and ethanol.

  As a method of controlling the average aggregate particle size during pulverization by wet pulverization, etc., a method of adjusting the pulverization time, a method of changing the particle size of a pulverizing medium such as beads, a method of adjusting pulverization energy, and a method of combining these methods Etc. can be adopted.

  The average aggregated particle size of the Mn source used in the pulverization, that is, in the firing step is 0.03 μm to 0.5 μm and 0.04 μm to 0.4 μm from the viewpoint of generating a primary particle size suitable for lithium manganate. Is preferable, and 0.05 to 0.3 μm is more preferable. Moreover, 0.01-0.1 micrometer is preferable from the same viewpoint, and the average primary particle diameter of the Mn source used at a baking process has more preferable 0.03-0.08 micrometer.

  The concentration during wet pulverization is preferably 1% by weight or more, more preferably 2% by weight or more, and particularly preferably 5% by weight or more from the viewpoint of productivity. Further, from the viewpoint of the grinding efficiency of the slurry, it is preferably 70% by weight or less, more preferably 60% by weight or less, and particularly preferably 50% by weight or less.

  Moreover, it is preferable to add a dispersing agent from a viewpoint of improving the grinding efficiency at the time of wet grinding. When a dispersant is used, an anionic, nonionic or cationic surfactant, or a polymer dispersant can be used as the dispersant, but a polymer dispersant is preferably used from the viewpoint of dispersion performance.

  Although various compounds can be used as the polymer dispersant, a polycarboxylic acid polymer dispersant having a plurality of carboxyl groups in the molecule and a polyamine polymer dispersant having a plurality of amino groups in the molecule A polymer dispersant having a plurality of amide groups in the molecule and a polymer dispersant containing a plurality of polycyclic aromatic compounds in the molecule are preferred.

  Examples of the polyamine polymer dispersant include comb polymers in which a polyester is grafted to a polyamine such as polyalkyleneamine, polyallylamine, and N, N-dimethylaminoethyl methacrylate.

  Examples of polycarboxylic acid-based polymer dispersants include copolymers of (meth) acrylic acid and (meth) acrylic acid esters, various amines such as maleic anhydride copolymer and alkylamine, and amidated and esterified products of alcohols, Examples thereof include a polycarboxylic acid polyester such as a poly (meth) acrylic acid copolymer and a comb polymer grafted with a polyalkylene glycol.

  As a polymer dispersant having a plurality of amide groups in the molecule, polyamide, polyvinyl pyrrolidone, poly N, N-dimethylacrylamide copolymer obtained by condensation reaction or polyester or polyalkylene glycol is grafted on this. Type polymer and the like.

  Examples of the polymeric dispersant containing a polycyclic aromatic compound include copolymers of vinyl monomers having a pyrene or quinacridone skeleton and various monomers.

  These dispersing agents can be used alone or in admixture of two or more kinds of dispersing agents. A suitable addition amount in the case of using a dispersant is 0.05% by weight to 10% by weight.

  The slurry may be dried by spray drying, static drying, or drying while flowing. The drying temperature is preferably in the range of a temperature exceeding the boiling point of the solvent to 400 ° C.

  In the present invention, the Li source is preferably wet pulverized in the same manner as the Mn source, and even when an insoluble substitutional element M compound is used, the wet pulverization can be similarly performed.

  From the viewpoint of reactivity with the Mn source, the average aggregate particle size of the Li source used after the pulverization, that is, in the firing step is preferably 0.03 μm to 0.5 μm, and more preferably 0.05 to 0.3 μm. Moreover, 0.01-0.5 micrometer is preferable from the same viewpoint, and the average primary particle diameter of Li source used at a baking process has more preferable 0.03-0.3 micrometer.

  In the firing step, firing is performed in a state where the Mn source and at least the Li source are mixed. However, the firing may be performed at any time before grinding, before grinding slurry drying, or after slurry drying. However, from the viewpoint of uniformly mixing, it is preferable to mix the two in a slurry state after pulverization using a disperser such as a disper or a homomixer.

  The mixing ratio is preferably such that the Li / Mn molar ratio is preferably 0.9 to 1.1, more preferably 0.98 to 1.02. When the substitution element M is contained, the molar ratio of Li / (Mn + M) is preferably in the above range.

  In the present invention, primary particles are produced by sintering by firing using aggregated particles of a Mn source. At this time, if the agglomerated particles are in close contact with each other, the primary particles of lithium manganate produced by the secondary agglomeration grow to a larger size, making it difficult to control the primary particle size. From such a point of view, a substance that acts as a spacer for separating the agglomerated particles of the Mn source may be added.

  Specifically, such a substance that disappears during the firing process is preferable, and examples thereof include carbon materials such as carbon black and polymer materials. These are added to a slurry of 0.5 to 10% by weight, preferably 1 to 8% by weight of the raw material manganese oxide, mixed and dried to act as a buffer material between the aggregated particles of the Mn source, It becomes easier to control the primary particle size of lithium manganate.

  The firing temperature is preferably 400 ° C. or higher, 600 ° C. or higher, or 750 ° C. or higher from the viewpoint of crystallinity, and 1100 ° C. or lower, more preferably 1000 ° C. or lower, 900 ° C. or lower from the viewpoint of preventing compositional deviation due to Li evaporation. Is more preferable. The firing time is preferably about 1 to 36 hours, although it depends on the firing temperature.

  The production method of the present invention includes a pulverization step of dry pulverizing the fired product obtained as described above to obtain lithium manganate having an average aggregate particle diameter of 10 μm or less. Lithium manganate is pulverized to have a preferable average agglomerated particle size, but dry pulverization is performed from the viewpoint of preventing a decrease in crystallinity due to excessive pulverization.

  The dry pulverization methods include impact pulverizers such as rotor speed mills and hammer mills, dry rolling ball mills, dry vibratory ball mills, dry planetary mills, dry media pulverizers such as medium agitation mills, and airflow pulverization such as jet mills. And a method using a machine. Among these, a method using an impact pulverizer such as a rotor speed mill or a hammer mill is preferable from the viewpoint of appropriate pulverization.

  The average agglomerated particle size of lithium manganate after dry pulverization is preferably 10 μm or less, more preferably 8 μm or less, from the viewpoint of improving the insertion / desorption ability of Li and maintaining the smoothness of the coating film. Moreover, when producing a coating film as a positive electrode of a battery, from the viewpoint of reducing the amount of binder, it is preferably 0.5 μm or more and 0.7 μm or more.

  Further, the primary particle size of the lithium manganate after dry pulverization is 0.03 μm to 0.5 μm from the viewpoint of suppressing elution of Mn into the electrolyte and ensuring stable high-speed discharge characteristics (rate characteristics). Preferably, 0.05 to 0.3 μm is more preferable.

The BET specific surface area of the lithium manganate after dry pulverization is preferably 4 m ² / g or more from the viewpoint of the permeability of the electrolytic solution, and preferably 40 m ² / g or less from the viewpoint of reducing the binder amount when producing the positive electrode. That is, 4-40 m < ² > / g is preferable, 4-20 m < ² > / g is more preferable, and 4-10 m < ² > / g is still more preferable.

  In addition, the lithium manganate after dry pulverization preferably has a peak pore diameter measured by a mercury porosimeter of 0.1 to 0.5 μm from the viewpoint of achieving smooth movement of Li ions, 0.5 μm is more preferable, and 0.2 to 0.5 μm is still more preferable.

  Furthermore, the lithium manganate after dry pulverization preferably has a total pore volume measured by a mercury porosimeter of 0.8 ml / g to 2 ml / g from the viewpoint of the balance between porosity and energy density necessary for Li transfer. .

  Moreover, as for the X-ray-diffraction spectrum (XRD) peak strongest intensity | strength of lithium manganate, the value obtained by the method as described in an Example has the preferable 2500-50000 from a viewpoint of a high-speed discharge characteristic.

  The lithium manganate obtained by the present invention can be suitably used as a positive electrode active material for a lithium battery. When using lithium manganate as a positive electrode active material, for example, a positive electrode active material, a conductive material such as carbon black, a slurry mixed with a binder, and a solvent are applied to a metal foil serving as a current collector and dried. A lithium battery is manufactured by stacking together with a negative electrode and a separator and injecting an electrolyte solution.

  A lithium battery produced using the lithium manganate obtained by the present invention has excellent high-speed discharge characteristics. In the battery characteristics evaluation described later, the ratio of the discharge amount of 60C to 55C is preferably 55% or more, and more preferably 60% or more.

  According to the method for producing lithium manganate of the present invention, since manganese oxide having a specific average aggregated particle size is used, it is easy to obtain lithium manganate having an appropriate average primary particle size and average aggregated particle size after firing and pulverization, It is thought that smooth insertion / extraction of Li tends to occur. In addition, since the calcined product obtained using such raw material particles is dry-pulverized to have an average aggregate particle size of 10 μm or less, the crystallinity (crystal grain size, etc.) is reduced as compared with wet pulverization. It is considered that the lithium insertion / extraction function of lithium manganate is easily developed. As a result, it is considered that a method for producing lithium manganate that is excellent in high-speed discharge characteristics particularly in a lithium battery as compared with conventional lithium manganate can be provided.

  The lithium manganate of the present invention is obtained by the production method of the present invention as described above. As described above, the lithium manganate of the present invention is excellent in high-speed discharge characteristics particularly in a lithium battery as compared with conventional lithium manganate.

  The use of batteries using lithium manganate is not particularly limited. For example, it can be used for electronic devices such as notebook computers, ebook players, DVD players, portable audio players, video movies, portable TVs, and cell phones, and cordless cleaning. It can be used in consumer equipment such as machines, cordless power tools, batteries for electric cars, hybrid cars, etc., and auxiliary power sources for fuel cell cars. Among these, it is suitably used as a battery for automobiles that require particularly high output.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

(1) Average agglomerated particle diameter Using a laser diffraction / scattering particle size distribution analyzer (LA920 Horiba, Ltd.), in the case of slurry, the dispersion medium is the same as that of the slurry. The particle size distribution after irradiation was measured with a relative refractive index of 1.5.

(2) Average primary particle diameter 50 primary particles are extracted from an SEM image at a magnification at which 50 to 100 primary particles enter a microscope field of view taken by a field emission scanning electron microscope (S-4000 Hitachi), The average value obtained by measuring the ferret diameter was defined as the average primary particle diameter. The Feret diameter is a tangential diameter in a fixed direction, and is described in literature (Yasuo Arai, “Materials Chemistry of Powders”, Baifukan Co., Ltd., September 10, 1987, first edition, pages 160-161). In this way, the distance between tangent lines when a tangent line in a specific direction (direction is one direction) is drawn for each particle. In addition, when the sample was a slurry, what removed the solvent was observed.

  For example, the powder obtained in Synthesis Example 2 corresponding to Example 1 becomes the SEM image shown in FIG. 1, but according to the measurement method as described above, the average primary particle size is 0.3 μm.

(3) BET specific surface area The BET specific surface area was measured using the specific surface area measuring apparatus (Shimadzu Flowsorb III2305). In addition, when the sample was a slurry, the measurement was performed using the sample from which the solvent was removed.

(4) Peak pore diameter and total pore volume Using a mercury intrusion type pore distribution measuring device (pore sizer 9320, Shimadzu Corporation), the pore volume in the range of 0.008 μm to 200 μm was measured, and the obtained value was The total pore volume was used. Moreover, the peak top pore diameter of the maximum peak among the pore distribution peaks obtained by measurement was defined as the peak pore diameter.

(5) XRD peak strongest intensity Using a X-ray diffractometer (RINT2500VPC Rigaku), the sample was measured at an output of 120 kV, 40 mA, a scanning speed of 10 ° / min, and sampling of 0.01 °, and d = near 4.7. Was the XRD strongest peak intensity.

(6) Preparation of Battery 5 parts by weight of carbon black, 5 parts by weight of PVDF powder, and 75 parts by weight of N methylpyrrolidone were uniformly mixed with 40 parts by weight of lithium manganate to prepare a coating paste. The paste was uniformly coated on an aluminum foil (thickness 20 μm) used as a current collector using a coater, and dried at 140 ° C. over 10 minutes. After drying, the film was formed into a uniform film thickness with a press machine, and then cut into a predetermined size (20 × 15 mm ² ) to obtain a test positive electrode. At this time, the thickness of the electrode active material layer was set to 25 μm. A test cell was prepared using the test positive electrode. A metal lithium foil was cut into a predetermined size for the negative electrode, and Celgard # 2400 was used for the separator. As the electrolytic solution, 1 mol / l LiPF ₆ / EC: DEC (1: 1 vol%) was used. The test cell was assembled in a glove box under an argon atmosphere. After the test cell was assembled, it was allowed to stand at 25 ° C. for 24 hours, and then high-speed charge / discharge characteristics were evaluated.

(7) Fast discharge characteristics evaluation After performing constant current charge / discharge on the test cell at 0.2 CA, (1) capacity (A) charged at constant current at 0.5 CA, and then charged at constant current at 1 CA (A), Further, (2) the ratio of the capacity (B) discharged at a constant current of 0.5 CA and then discharged at a constant current of 60 CA was defined as a fast discharge characteristic.
High-speed discharge characteristics (%) = B / A × 100

Synthesis example 1
15 parts by weight of MnO ₂ having an average primary particle size of 0.03 μm and an average aggregated particle size of 34 μm are mixed with 85 parts by weight of ethanol and wet pulverized by a bead mill. The average primary particle size is 0.03 μm and the average aggregated particle size is 0.00. A slurry of 7 μm MnO ₂ was obtained. Next, 10 parts by weight of lithium carbonate having an average primary particle diameter of 25 μm and an average aggregated particle diameter of 84 μm is mixed with 90 parts by weight of ethanol, and wet pulverized by a bead mill, and the average primary particle diameter is 0.06 μm and the average aggregated particle diameter is 0.3 μm. A slurry of lithium carbonate was obtained. 100 parts by weight of the obtained MnO ₂ slurry and 31.86 parts by weight of lithium carbonate slurry (Li / Mn molar ratio = 1/2) were mixed with a disper and evaporated to dryness with a rotary evaporator. The obtained powder was crushed in a mortar and baked at 850 ° C. for 5 hours.

The obtained powder was dry-pulverized with a rotor speed mill (P-14 Flitchchu) to obtain a powder having an average primary particle size of 0.7 μm and an average aggregated particle size of 1.2 μm. As a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Synthesis example 2
15 parts by weight of MnO ₂ having an average primary particle size of 0.03 μm and an average aggregated particle size of 34 μm are mixed with 85 parts by weight of ethanol and wet pulverized by a bead mill. The average primary particle size is 0.03 μm and the average aggregated particle size is 0.00. A slurry of 3 μm MnO ₂ was obtained. Next, 10 parts by weight of lithium carbonate having an average primary particle diameter of 25 μm and an average aggregated particle diameter of 84 μm are mixed with 90 parts by weight of ethanol and wet-pulverized by a bead mill, and carbonic acid having an average primary particle diameter of 0.06 μm and an average aggregated particle diameter of 0.3 μm. A lithium slurry was obtained. 100 parts by weight of the obtained MnO ₂ slurry and 31.86 parts by weight of lithium carbonate slurry (Li / Mn molar ratio = 1/2) were mixed with a disper and evaporated to dryness with a rotary evaporator. The obtained powder was crushed in a mortar and baked at 850 ° C. for 5 hours. The obtained powder was dry-pulverized with a rotor speed mill (P-14 Flitchchu) to obtain a powder having an average primary particle size of 0.3 μm and an average aggregated particle size of 1.1 μm. As a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Synthesis example 3
400 g of MnO ₂ having an average primary particle size of 0.03 μm and an average aggregated particle size of 34 μm was mixed with 2267 g of ethanol and wet-pulverized with a dyno mill (Shinmaru Enterprises MULTI LAB type), the average primary particle size was 0.03 μm, the average A slurry of MnO _{2 with} an agglomerated particle size of 0.5 μm was obtained. At that time, as pulverization conditions of the dyno mill (capacity 0.6 liter), 1784 g of φ1 mm zirconia beads were filled, and the whole slurry was passed twice at a rotational speed of 14 m / s at a peripheral speed of 185 g / min (2 The slurry was pulverized by the method of passing. By using the obtained slurry of MnO ₂ and carrying out the other steps up to dry grinding under the same conditions as in Synthesis Example 2, a powder having an average primary particle size of 0.5 μm and an average aggregated particle size of 1.3 μm is obtained. It was. As a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Synthesis example 4
Using 3326.5 g of a slurry of MnO ₂ having an average aggregate particle diameter of 0.5 μm obtained in Synthesis Example 3, it was wet pulverized by dyno mill (MULTI LAB type manufactured by Shinmaru Enterprises), and the average primary particle diameter was 0.03 μm. A slurry of MnO ₂ having an average aggregate particle diameter of 0.2 μm was obtained. At that time, the grinding conditions of the dyno mill were filled with 1836 g of φ0.2 mm zirconia beads instead of the φ1 mm zirconia beads used in Synthesis Example 3, and the total amount of slurry was 185 g / min at a peripheral speed of 14 m / s. This was carried out under the condition of circulating and grinding at a speed for 240 minutes. Using the obtained slurry of MnO ₂ , the other steps up to dry grinding were carried out under the same conditions as in Synthesis Example 2 to obtain a powder having an average primary particle size of 0.2 μm and an average aggregated particle size of 1 μm. As a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Synthesis example 5
15 parts by weight of LiMn ₂ O ₄ obtained in Synthesis Example 1 was mixed with 85 parts by weight of ethanol, and wet pulverized with a bead mill to obtain a slurry having an average primary particle size of 0.3 μm and an average aggregated particle size of 0.3 μm. Ethanol was removed from the slurry using a rotary evaporator to obtain a powder having an average primary particle size of 0.3 μm and an average aggregated particle size of 0.3 μm. As a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 1
The powder obtained in Synthesis Example 2 was measured for BET specific surface area, pore distribution, pore volume, and XRD peak strongest intensity. A battery was prepared using this powder, and the high-speed discharge characteristics were measured. The results are shown in Table 1. In the table, “product primary particle diameter” and “product aggregate particle diameter” represent “average primary particle diameter” and “average aggregate particle diameter” of the powder obtained in Synthesis Example 2.

Example 2
The powder obtained in Synthesis Example 4 was measured for BET specific surface area, pore distribution, pore volume, and XRD peak strongest intensity. A battery was prepared using this powder, and the high-speed discharge characteristics were measured. The results are shown in Table 1. In the table, “product primary particle size” and “product aggregate particle size” represent “average primary particle size” and “average aggregate particle size” of the powder obtained in Synthesis Example 4.

Example 3
The powder obtained in Synthesis Example 3 was measured for BET specific surface area, pore distribution, pore volume, and XRD peak strongest intensity. A battery was prepared using this powder, and the high-speed discharge characteristics were measured. The results are shown in Table 1. In the table, “product primary particle diameter” and “product aggregate particle diameter” represent “average primary particle diameter” and “average aggregate particle diameter” of the powder obtained in Synthesis Example 3.

Comparative Example 1
The BET specific surface area, pore distribution, pore volume, and XRD peak strongest strength of the powder of Synthesis Example 1 were measured. A battery was prepared using this powder, and the high-speed discharge characteristics were measured. The results are shown in Table 1. In the table, “product primary particle diameter” and “product aggregate particle diameter” represent “average primary particle diameter” and “average aggregate particle diameter” of the powder obtained in Synthesis Example 1.

Comparative Example 2
The powder obtained in Synthesis Example 5 was measured for BET specific surface area, pore distribution, pore volume, and XRD peak strongest intensity. A battery was prepared using this powder, and the high-speed discharge characteristics were measured. The results are shown in Table 1. In the table, “product primary particle diameter” and “product aggregate particle diameter” represent “average primary particle diameter” and “average aggregate particle diameter” of the powder obtained in Synthesis Example 5.

As shown in Table 1 the results of Example 1-3 (Synthesis Example 2-4) and Comparative Example 1 (Synthesis Example 1) than, LiMn ₂ having an average primary particle diameter corresponding to an average agglomerated particle size of the MnO ₂ It can be seen that O ₄ is obtained. Moreover, it turns out that the fine lithium manganate obtained in Example 1 has higher high-speed discharge characteristics than the lithium manganate having a large average primary particle diameter in Comparative Example 1. In addition, in the fine particle lithium manganate of Comparative Example 2 obtained by wet pulverization of lithium manganate, the crystallinity is lowered although the average primary particle diameter is the same as that of Example 1. It can be seen that the high-speed discharge characteristics deteriorate.

Scanning electron micrograph of the powder obtained in Synthesis Example 2, corresponding to Example 1.

Claims (4)

A firing step of firing in a state in which manganese oxide having an average aggregated particle size of 0.03 to 0.5 μm and at least a lithium compound are mixed, and an average aggregated particle size of 10 μm or less by dry-grinding the obtained fired product a method of manufacturing a spinel type lithium manganate and a grinding step to obtain a lithium manganate,
The BET specific surface area of the lithium manganate obtained in the pulverization step is 4 to 40 m ² / g, the peak pore diameter is 0.1 to 0.5 μm and the total pore volume is 0.8 ml as measured with a mercury porosimeter. / G-2ml / g of spinel type lithium manganate manufacturing method. The method for producing spinel-type lithium manganate according to claim 1, wherein an average primary particle size of lithium manganate obtained in the pulverization step is 0.03 to 0.5 µm. The method for producing spinel-type lithium manganate according to claim 1 or 2, wherein the average aggregate particle diameter of lithium manganate obtained in the pulverization step is 0.5 to 10 µm. The method for producing spinel type lithium manganate according to any one of claims 1 to 3 , wherein the lithium manganate is for a lithium battery.

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