JP4359667B2 - Method for producing lithium manganate powder, produced lithium manganate powder, electrode and lithium secondary battery - Google Patents

Description

  The present invention relates to a method for producing a powder that can be used as various industrial materials, and more specifically, in a method for producing a lithium manganate powder that is a positive electrode material of a lithium-based secondary battery. The present invention relates to a method for producing a lithium manganate powder capable of homogenizing as much as possible and homogenizing the material of the powder.

  Industrial powders are broadly classified into inorganic powders and organic powders. Inorganic powders include ceramic powders, metal powders, metal oxide powders, etc., and organic powders are plant-based powders. There are powder and animal powder. The inorganic powder is generally formed by firing a raw material powder at a high temperature. For example, alumina powder is fired at a high temperature of 1400 ° C. for 1 hour, and spinel powder needs to be fired at a high temperature of 1550 ° C. for 1 hour. Further, soda alumina powder needs to be fired at a high temperature of 1600 ° C. for 2 hours. As described above, it is important to keep the firing temperature constant and keep the firing time constant for the formation of the powder.

In recent years, electronic devices and the like are particularly required to be small and light. In particular, the demand for lithium secondary batteries as equipment power sources for mobile phones, notebook computers, and camera-integrated video is rapidly expanding. A lithium secondary battery is composed of a positive electrode, an electrolyte, and a negative electrode, and employs a mechanism in which Li ⁺ is transferred from the positive electrode to the negative electrode for charging, and conversely, Li ⁺ is transferred from the negative electrode to the positive electrode for discharging. Therefore, both the negative electrode and the positive electrode need to be formed of a material that can occlude and release Li ⁺ .

In a conventional lithium secondary battery, a lithium composite oxide is used as a positive electrode material. For example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and the like. Among them, LiCoO ₂ is most widely used.

These positive electrode materials are composed of lithium composite oxide powder, but the structure of the particles constituting the powder is common. That is, the particles are made of crystal and are often composed of layered crystals or porous crystals. It is a mechanism that occludes Li ^{+ in} the internal space of these crystal bodies and releases Li ⁺ from the internal space.

  Therefore, when manufacturing the powder constituting the positive and negative electrode materials of the lithium secondary battery, it is particularly important to control the chemical composition and the microstructure. The production method includes a solid phase reaction method, a liquid phase reaction method, a spray pyrolysis method and the like. In particular, the spray pyrolysis method related to the present invention includes an internal combustion system and an external combustion system.

  USP 3,230,064 is known as a known technique of the internal combustion system in the spray pyrolysis method. This technique is the prior art that first introduced flame swirl.

  Japanese Unexamined Patent Publication No. 5-75685 is known as a known technique of the external combustion method in the spray pyrolysis method. This known technique employs a system in which the feedstock is allowed to flow in the free fall direction from the upper part of the cylindrical reaction section.

Non-patent technical literature includes “development and commercialization of a ferrite material manufacturing process by co-roasting of iron and manganese solutions” published in “Powder and Powder Metallurgy”, Vol. 45, No. 7 (1998) . This paper is also a known technique of the internal combustion system in the spray pyrolysis method. Specifically, a method is adopted in which the feedstock is allowed to flow from the upper part of the cylindrical reaction section in the free fall direction and the raw material mist is directly heated by a combustion burner inside the reaction furnace.
USP 3,230,064 Japanese Patent Laid-Open No. 5-75685 “Powder and powder metallurgy” Vol. 45, No. 7 (1998) “Development and commercialization of a ferrite material manufacturing process by co-roasting of iron and manganese solutions”

  FIG. 20 is a cross-sectional view of a cylindrical reaction portion by an internal combustion system disclosed in Patent Document 1 (USP 3,230,064). The powder raw material is supplied from the raw material supply unit through the pipe 101 by compressed air and sprayed upward from the powder raw material ejection unit 102 in an inverted conical shape. For this reason, the powder raw material is given an initial speed in the upward direction during spraying, and this initial speed reaches a considerably high speed. In addition, torch burners 103 and 103 are arranged on the left and right in the middle of the cylindrical reaction part, and spray nozzles 104 and 104 are provided at the tip thereof. A flame is ejected from the nozzles 104 and 104 toward the center, but the flame surface is only one surface. Therefore, since the powder raw material rising at high speed instantaneously passes through the flame surface, the time during which the powder raw material is fired is extremely short and it is difficult to ensure a sufficient firing time. Further, since the powder raw material is sprayed directly upward, all raw material particles having a variation in particle diameter pass through the flame surface and are fired. Therefore, the particle size of the produced powder particles naturally has a drawback of being distributed over a wide range.

  21 is a cross-sectional view taken along line AA in FIG. Six burners 103 are arranged at equal intervals in the circumferential direction, and the radiant flame is configured to be injected at a position eccentric from the center. Thus, the flame is swirled and a flame swirl is formed. Since the above-mentioned powder raw material is fired on a flame swirl flow, it is possible to increase the reaction time by the swirl time. However, since there is only one flame surface, the high temperature region necessary for the reaction is extremely thin, and there is a weak point that unreacted powder continues. The flame swirl initially swirls while drawing a small circle and rises by buoyancy, but the firing temperature drops rapidly as it rises. Therefore, a large temperature difference is generated between the lower part and the upper part of the flame swirl flow, and it is difficult to form a uniform temperature firing space.

  FIG. 22 is a vertical cross-sectional view of a reactor using an external combustion method disclosed in Patent Document 2 (Japanese Patent Publication No. 5-75685). This reactor includes a powder raw material supply unit 106 that supplies powder raw material in a free-fall manner, a heater 107 that externally heats the cylindrical reaction unit 105 in multiple stages, and cooling that cools the generated powder. And a powder delivery device 109 for discharging the produced powder.

  The feature of this prior art is that the cylindrical reaction part 105 is heated from the outside, so that the temperature distribution inside the reaction part tends to be relatively uniform when the reaction tube diameter is relatively small. However, the external heating method has the disadvantage that when the reaction tube diameter is large, a temperature deviation is likely to occur on the horizontal surface, and it is difficult to obtain a uniform thermal decomposition reaction, and much of the heat energy is dissipated to the outside. However, there is a particular problem from the viewpoint of energy saving in recent years. In addition, since this technology supplies the raw material powder while freely dropping downward, all of the produced target powder is collected integrally. When the raw material powder has a large size non-uniformity, the resulting powder also has the same size non-uniformity, and there is a drawback that these are collected and mixed together. That is, size uniformity of the produced powder cannot be obtained. Furthermore, when impurities are contained in the feedstock, mixing of the impurities cannot be prevented, and even when impurities are present in the reaction furnace, there is a weak point that the impurities fall into the produced powder.

  As non-patent literature, there is “development and commercialization of ferrite material manufacturing process by co-roasting method of iron / manganese solution”, but this prior art is also an internal combustion system in the flame spray pyrolysis method. Has similar disadvantages.

  Thus, the conventional manufacturing method has various drawbacks. Therefore, it is clear that the same disadvantages are caused even when the above-described conventional manufacturing method is applied when manufacturing lithium manganate powder for a lithium secondary battery. Accordingly, an object of the present invention is to provide a method for producing a lithium manganate powder, in which the thermal reaction time can be adjusted freely, the particle size is uniform, the homogeneity of the particles is ensured, and contamination of impurities can be prevented. That is.

  The present invention has been made to solve the above problems, and a first aspect of the present invention is a method for producing a lithium manganate powder which is an electrode material of a lithium-based secondary battery. A raw material of lithium manganate powder that forms a flame swirl flow in a plurality of axially spaced cross-sections that are axially separated in a cylindrical reaction section that generates powder, and that rises from below the cylindrical reaction section in the upward direction The raw material mist containing at least the raw material mist is supplied, the raw material mist is introduced into the plurality of flame swirl flows, and the raw material mist is swirled. It is a manufacturing method of the lithium manganate powder which forms.

  The 2nd form of this invention is a manufacturing method of the lithium manganate powder which the said raw material mist mix | blended the additive with the raw material of the lithium manganate powder.

  The 3rd form of this invention is a manufacturing method of the lithium manganate powder | flour which makes a flame swirl flow swirl along the inner surface of a cylindrical reaction part.

  According to a fourth aspect of the present invention, a lithium manganate powder is provided with a raw material mist storage part for storing the raw material mist below the cylindrical reaction part, and a filter for passing the raw material mist above the raw material mist storage part. It is a manufacturing method.

The fifth aspect of the present invention is a method for producing lithium manganate powder in which a raw material solution is sprayed in the horizontal direction with respect to the raw material mist storage part to form a raw material mist and the raw material mist is retained in the raw material mist storage part.

  In the sixth aspect of the present invention, the raw material mist is sucked and raised from the raw material mist reservoir by suction means provided outside the cylindrical reaction part, and the powder produced from the raw material mist in the flame swirl flow is This is a method for producing a lithium manganate powder that is led out of the reaction chamber and separated and recovered from the exhaust gas.

  The 7th form of this invention is a manufacturing method of the lithium manganate powder which rebakes the lithium manganate powder manufactured by the manufacturing method in any one of the 1st form-the 6th form.

  The 8th form of this invention is the lithium manganate powder manufactured by the manufacturing method in any one of 1st form-7th form.

  A ninth aspect of the present invention is an electrode for a lithium secondary battery in which an electrode is formed from lithium manganate powder produced by the production method of any one of the first to seventh aspects.

  A tenth aspect of the present invention is a lithium secondary battery in which an electrode formed from a lithium manganate powder produced by the production method of any one of the first to seventh aspects is disposed as a positive electrode.

  According to the first aspect of the present invention, a flame swirl flow is formed in each of a plurality of cross-sections orthogonal to each other in the axial direction in the cylindrical reaction section that generates the powder. The firing temperature can be kept constant in the range of the flame swirl flow. If the flame swirl flow is further arranged in multiple stages, there is an advantage that a large firing space maintained at a constant temperature can be set, and the size of the firing space can be freely adjusted by adjusting the number of stages. That is, since the raw material mist can be fired at a constant temperature for a desired time, a homogeneous powder of lithium manganate can be produced. Moreover, since the multistage flame swirl | flow is comprised continuously, the turning amount of raw material mist can be adjusted freely and the baking time of raw material mist can be controlled.

According to the 2nd form of this invention, the electrode performance of a lithium secondary battery can be improved by mix | blending various additives with the raw material of lithium manganate powder. As the additive, any metal element and / or non-metal element can be selected, and examples thereof include Co, Ni, Al, and Mg. When the raw material of the lithium manganate powder to which these additives are added is fired, the formed powder crystals have a large number of pores. Therefore, when the powder of the present invention is used as an electrode material of a lithium secondary battery, particularly a positive electrode material, a large amount of Li ⁺ is occluded and released in the crystal vacancies of the electrode. As a result, the electrode performance of the lithium secondary battery can be dramatically improved and the intended purpose can be achieved.

  According to the third aspect of the present invention, the flame swirl flow is formed so as to extend along the inner surface of the cylindrical reaction part, so that the flame swirl flow having a large swirl radius is formed in the entire inside of the cylindrical reaction part. Can do. Since the raw material mist swirls on this large flame swirl, the time for staying in this flame swirl becomes longer, the thermal decomposition reaction occurs sufficiently, and high quality powder can be produced. Moreover, since this large flame swirl is formed in multiple stages, there is no vertical temperature difference between the lower part and the upper part of the flame swirl, and a large firing space with a constant temperature can be formed. Accordingly, it is possible to form a homogeneous powder by being sufficiently fired. Furthermore, the firing temperature and firing time can be freely adjusted by controlling the heating power and swirl time of the flame swirl flow.

  According to the fourth aspect of the present invention, since the raw material mist storage part for storing the raw material mist is provided below the cylindrical reaction part, the raw material mist sprayed on the raw material mist storage part is initially in a disturbed state. Uniform floating state over time. As a result, a mist having a larger particle diameter or a larger mass than the normal range existing in the raw material mist falls downward or adheres to the wall surface. That is, the particle size and mass of the raw material mist floating in the space become constant, and the selected uniform raw material mist can be supplied to the upper cylindrical reaction section. Moreover, since the filter which passes raw material mist above the raw material mist storage part is arrange | positioned, the raw material mist storage part can be separated from a cylindrical reaction part by installation of this filter. This filter makes it possible to further sort the raw material mist, and it is possible to receive the powder partially falling from the cylindrical reaction part.

  According to the fifth aspect of the present invention, since the raw material solution is sprayed in the horizontal direction with respect to the raw material mist reservoir to form the raw material mist, the raw material mist is not given the initial velocity in the vertical direction. As a result, the velocity component through which the raw material mist penetrates the flame swirl becomes small, the time for staying in the flame swirl becomes long, and it can contribute to the production of homogeneous and uniform powder. If the raw material solution is sprayed in an opposing state, the horizontal velocity component of the raw material mist is canceled out, the floating raw material mist stays floating only by buoyancy, and the selection of the raw material mist by mass and particle size can be further enhanced.

  According to the sixth aspect of the present invention, since the raw material mist is sucked and raised from the raw material mist reservoir by the suction means provided outside the cylindrical reaction part, the rising speed of the raw material mist is adjusted by adjusting the suction force. And the firing time for forming the powder can be controlled. Further, since the formed powder is sucked from the upper part of the cylindrical reaction part, disturbance of the staying mist due to the fall of the formed powder can be prevented. In addition, since the powder can be collected outside the cylindrical reaction section, the production efficiency of the powder can be improved simultaneously with the production and collection of the powder. Moreover, the particle size of the recovered powder can be selected by changing the mesh degree of the recovery filter. If the filters having different mesh degrees are arranged in multiple stages, the sorting efficiency can be improved.

  According to the seventh aspect of the present invention, since the lithium manganate powder produced by the production method of any one of the first to sixth aspects is refired, the unfired powder present in the product powder The body can be completely fired and the thermal decomposition of the undecomposed powder can be promoted. Furthermore, the crystallinity of the resulting powder can be improved by this refiring. Further, the specific surface area can be controlled by refiring. In this manner, when a powder coating is formed using the refired powder, the coating performance (coating property) to the electrode substrate can be improved. As a result, the overall performance of the lithium manganate powder can be improved.

  According to the 8th form of this invention, the lithium manganate powder manufactured by the manufacturing method in any one of the 1st form-the 7th form can be provided, and the high performance powder mentioned above can be supplied to the market.

According to the 9th form of this invention, the electrode for lithium secondary batteries formed from the lithium manganate powder manufactured by the manufacturing method in any one of 1st form-7th form can be provided. Since the number and size of the pores of this porous electrode can be freely adjusted according to the present invention, the Li ⁺ release and storage characteristics can be improved, and an electrode for a high-performance lithium secondary battery can be provided.

  According to a tenth aspect of the present invention, there is provided a lithium secondary battery in which an electrode formed from a lithium manganate powder produced by the production method of any one of the first to seventh aspects is disposed as a positive electrode. it can. In particular, the lithium manganate electrode according to the present invention has excellent positive electrode characteristics, and a lithium secondary battery incorporating this electrode has an excellent charge / discharge characteristic.

  Embodiments of a method for producing lithium manganate powder, a produced lithium manganate powder, an electrode, and a lithium secondary battery according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a powder production apparatus 1 that realizes a first embodiment of a method for producing a lithium manganate powder according to the present invention. The powder production apparatus 1 includes a cylindrical reaction unit 11, a powder separation unit 12, and a suction machine 13, and each member communicates with ducts 14 and 15.

  The cylindrical reaction part 11 is a hollow body, and is roughly divided into a raw material mist supply part 21, a raw material mist storage part 22, and a reaction part 23. The raw material mist supply unit 21 is provided on the lower side of the cylindrical reaction unit 11 and is arranged to inject the raw material mist M toward the raw material mist storage unit 22. A reaction unit 23 is continuously provided above the raw material mist storage unit 22.

  The powder separation unit 12 has a built-in collection member 24 for collecting the powder, and the exhaust gas passes through the collection member 24 so that the powder and the exhaust gas are separated. The collection member 24 is made of a filter material such as a bag filter.

  The suction machine 13 is provided so as to suck the inside of the cylindrical reaction unit 11, the duct 14, the powder separation unit 12, and the duct 15, and discharge the exhaust gas that has passed through the recovery member 24 to the outside. Accordingly, a fluid flow from the raw material mist supply unit 21 to the duct 14 through the raw material mist storage unit 22 and the reaction unit 23 is formed in the cylindrical reaction unit 11 by the action of the suction device 13.

  The operation of the tubular reaction unit 11 will be further described in detail. The raw material mist supply unit 21 is disposed on the side of the raw material mist storage unit 22, and is attached to an introduction pipe 31 having a trumpet shape that extends toward the raw material mist storage unit 22 and a small-diameter side end of the introduction pipe 31. 2 fluid nozzles 32. When the raw material solution S containing the powder raw material is sprayed from the two-fluid nozzle 32 in the arrow direction (horizontal direction) by the high-pressure carrier gas G, the raw material solution S is ejected as an infinite number of raw material mists M. It stays in the raw material mist reservoir 22 in a floating state. The high-pressure carrier gas G is preferably an inert gas such as air, nitrogen gas (N 2), helium, or argon.

  Since the raw material mist M is ejected in the horizontal direction, it is considered that the vertical velocity component of the raw material mist M is almost zero and has only the horizontal velocity component. Since the introduction pipe 31 has a trumpet shape, the raw material mist jet spreads in a trumpet shape and some vertical velocity component remains, but the entire jet may be considered to be zero. In FIG. 1, the jets are jetted in opposition from the left and right, and the jets collide with each other so that the horizontal velocity component becomes zero as a whole. Therefore, in the raw material mist storage unit 22, the raw material mist M is in a free floating state by buoyancy. The raw material mist storage unit 22 has a volume for diffusing the raw material mist, and has a function of temporarily storing the raw material mist M in a floating state.

  Inside the raw material mist reservoir 22, the raw material mist M is in a floating state and repeatedly collides with the wall surface. In general, the raw material mist has a higher particle size uniformity than the dry powder, but has a slight particle size distribution. Since the raw material mist having a large particle size easily adheres to the wall surface by the collision, the particle size uniformity of the raw material mist remaining in a floating state is further enhanced. The uniformity of the particle size and mass of the raw material mist group rising from the raw material mist reservoir 22 is extremely high.

  A filter 43 is interposed between the raw material mist storage unit 22 and the reaction unit 23. The filter 43 has a large opening 43a in FIG. 1, but can have various shapes such as a mesh shape or a punching metal shape. This filter 43 prevents the raw material mist blown into the raw material mist storage part 22 from blowing out to the reaction part 23, and has an effect of promoting the homogenization of the raw material mist in the raw material mist storage part 22. In a filter having a large opening 43a, this uniform promoting action is relatively small, but depending on the physical properties of the raw material mist, an opening, a mesh, and the like are properly used. In addition, the filter 43 can block the powder falling from the reaction unit 23 and prevent contamination in the raw material mist storage unit 22.

  The raw material mist M passes through the filter 43 from the raw material mist reservoir 22 and rises in the direction of arrow a by the suction force of the suction machine 13. Since the raw material mist M does not have an initial speed in the vertical direction, the ascending speed V is given only by the suction force of the suction machine 13. Therefore, the rising speed V of the raw material mist M can be freely adjusted by the suction force. Since the horizontal velocity component of the raw material mist M is very close to zero, the probability of colliding with the inner wall surface of the reaction portion 23 is small, and adhesion to the inner wall surface is prevented. Therefore, not only the production efficiency of the raw material mist is improved, but also powder falling from the inner wall surface is small, and the inside of the cylindrical reaction section 11 can be prevented from being contaminated.

  Above the reaction unit 23, a required number of burners 41 are arranged in two stages, spaced apart by a certain distance W. The first stage burners 41 are arranged at equal intervals in the circumferential direction of the cross section, and the second stage is also arranged in the same manner. The flame radiated from each burner 41 forms a flame swirl flow F inside the reaction section, and a number of flame swirl flows are continuously formed in the vertical direction by the upper and lower burners 41, 41. As a result, a high-temperature firing space 44 set at a constant temperature is formed over the range of the vertical distance L. The rising raw material mist M swirls and rises on the flame swirl, and is pyrolyzed in this process to change into powder. The size of the firing space 44 is determined by the number of stages of the burner 41 and the interval W.

  If the rising speed of the raw material mist M is V, the residence time in the firing space is given by L / V. This staying time becomes the thermal decomposition time of the raw material mist M, and this time is determined by the distance L or / and the rising speed V. Therefore, the thermal decomposition time has an advantage that it can be freely adjusted by the distance L and the rising speed V.

  FIG. 2 is a simplified cross-sectional view of the reaction section 23 at the burner position. The reaction portion 23 is formed of a cylindrical body having a circular cross section perpendicular to the axis, and four burners 41 capable of flame injection are disposed along the circumference of the cross section perpendicular to the axis. The number of burners is arbitrarily adjusted. Since the axial direction of the burner 41 is arranged along the inner peripheral surface, the flame radiated from the burner 41 flows along the circumferential surface, and a large flame swirl F is formed inside. A large number of flame swirl flows F are formed continuously in the vertical direction, so that a wide and constant temperature firing space 44 is formed between the lower flame swirl flow and the upper flame swirl flow.

  In addition, the raw material mist rising from the raw material mist storage section 22 also flows along this flame swirl flow, and the residence time becomes longer, so that the thermal decomposition time of the raw material mist M can be adjusted, and the length of the reaction section 23 can be shortened. It becomes. Further, as shown in FIG. 1, a cooling gas supply means 42 is disposed below the reaction unit 23. From the cooling gas supply means 42, a cooling gas, for example, cooling air is supplied. The temperature in the reaction unit 23 can be adjusted by adjusting the flow rate of the fuel to the burner 41 and adjusting the flow rate of the cooling gas from the cooling gas supply means 42. The cooling gas supply means 42 is not always necessary.

  Here, the powder production process in the cylindrical reaction part 11 which consists of the said structure is demonstrated. A raw material solution S for thermally decomposing lithium manganate powder is pumped to the two-fluid nozzle 32 by a pump not shown. For example, a solution of hydroxide, nitrate, sulfate, carbonate or the like is pumped, and the solution is sprayed into the introduction pipe 31 together with high-pressure air from the two-fluid nozzle 32 to generate a raw material mist M having an average diameter of about 10 μm. The The raw material mist M is sprayed from the introduction pipe 31 into the raw material mist reservoir 22, and when the raw material mist M having a relatively large diameter comes into contact with the wall surface, it gets wet and is trapped on the wall surface. Even if the material mist M having a relatively small diameter comes into contact with the material mist, the surface tension of the material mist itself is not greatly wetted, so that it floats in the material mist storage unit 22. As a result, the raw material mist M having a small diameter standard deviation remains. The remaining raw material mist M is sucked by the suction machine 13 and rises from the raw material mist storage part 22 through the opening 43a of the filter 43 and reaches the reaction part 23.

  In the illustrated example, four burners 41 of the reaction unit 23 are arranged in two stages, and the flame flow is injected in the circumferential direction in the reaction unit 23 to form a flame swirl flow F. Thereby, the temperature in the reaction part 23 becomes uniform, and the raw material mist M flows along the streamline of the flame swirl flow F. For this reason, it is possible to secure a sufficient residence time for the droplets to evaporate and thermally decompose. In this reaction part 23, thermal decomposition, melting, and synthesis occur instantaneously, and the target lithium manganate powder is produced.

  When lithium manganate is prepared using a nitrate solution, the lithium manganate powder may not be a fine powder having a desired shape under an atmosphere with a rapid temperature gradient. For this reason, it is necessary to strictly manage the rate of temperature rise in the reaction section 23, and control of the firing temperature is extremely important in the formation of powder. Accordingly, the present invention does not limit the number of burners 41, and the number of burners 41 in the circumferential direction and the number of stages in the axial direction are set so as to realize an axial temperature distribution corresponding to the processing solution in the reaction unit 23. It is set to the optimum value. Further, an optimum temperature distribution may be obtained by adjusting the fuel flow rate or the cooling gas flow rate of the burner 41 described above by a temperature control device (not shown).

  The lithium manganate powder obtained by pyrolysis in this way becomes an ultrafine powder having a primary particle size of the order of nanometers, and together with the exhaust gas, the powder separation part 12 passes from the cylindrical reaction part 11 via the duct 14. In the process leading to, the powder is cooled below the heat resistant temperature of the powder separation unit 12. The powder is introduced into the powder separation unit 12 together with the exhaust gas, separated from the exhaust gas by the recovery member 24, the powder is collected in the recovery member 24, and the exhaust gas that has passed through the duct 15 is To be discharged.

  In addition, the pressure in the cylindrical reaction part 11 may be lower than atmospheric pressure, may be atmospheric pressure, and may be higher than atmospheric pressure. Furthermore, the kind of atmospheric gas in the cylindrical reaction part 11 is not limited at all, and various atmospheric gases can be applied. When using a combustion reaction with oxygen, air or oxygen gas becomes the carrier gas G. When firing in a non-oxidizing atmosphere, an inert gas such as nitrogen, hydrogen, helium, or argon is used as the carrier gas G. Become.

Further, the present invention does not limit the cross-sectional shape of the reaction portion 23 to a circle, and it is sufficient that the inner periphery of the cross section perpendicular to the axis has a cylindrical shape having no corner portion smaller than 90 °, For example, it may have a cross-sectional shape such as a pentagon or a hexagon.
Furthermore, the present invention does not limit the number of raw material mist supply units 21, and the number of raw material mist supply units 21 may be one.
In addition, the present invention is not limited to the two-fluid nozzle 32, and the raw material mist may be ejected to the raw material mist supply unit 21 using a plurality of nozzles.

  FIG. 3 is an explanatory view showing a changing process by firing the raw material mist M. FIG. As the solvent evaporates, the raw material mist is precipitated and dried (Precipitation and Drying), then subjected to pyrolysis and finally sintered (Sintering).

  FIG. 4 is a schematic configuration diagram of a powder production apparatus 1 that realizes the second embodiment of the method for producing lithium manganate powder according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted, and different parts will be described below.

  The burners 41 are arranged in four stages up and down with a spacing W therebetween. This interval W can be arbitrarily set. As a result, a large high-temperature firing space 44 is formed. The size L of the firing space 44 is about three times as large as that in FIG. A large number of flame swirl flows F are formed in the large firing space 44, and the raw material mist M undergoes a sufficient firing reaction.

  FIG. 5 is a schematic configuration diagram of a powder production apparatus 1 that realizes the third embodiment of the method for producing lithium manganate powder according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted, and different parts will be described below.

  A mesh filter or a punching metal filter is used as the filter 43 disposed above the raw material mist reservoir 22. For this reason, the raw material mist M is separated and stored in the raw material mist storage part 22, the particle size and mass uniformity of the raw material mist M are further enhanced, and a homogeneous product powder can be produced. Further, even if there is powder falling from the reaction unit 23, it is received by the filter 43, and the inside of the raw material mist storage unit 22 can be normally held.

  Next, a production test of lithium manganate powder was performed. FIG. 6 is a crystal structure diagram of lithium manganate. The particles having this crystal structure are the target powder.

As a raw material for lithium manganate, lithium nitrate and manganese nitrate were used, and a 1 mol / dm ³ raw material solution was prepared so that the Li / Mn ratio was 0.54. This raw material solution was sprayed by a two-fluid nozzle and pyrolyzed in a flame swirl flow by a burner. LP gas was used as the flame fuel, and the temperature of the reaction section was set to 700 ° C to 1200 ° C. The resulting powder had low crystallinity and was refired at 700 ° C. Generally, the refiring temperature is in the range of 600 ° C to 1000 ° C. It was found that lithium manganate powder with desired performance can be produced by two-stage firing of firing and re-firing.

  This lithium manganate powder was slurried and applied to the substrate surface to form a positive electrode. A lithium secondary battery was fabricated using lithium as the negative electrode and a 1M LiPF6 EC / DMC (50/50 vol%) solution as the electrolyte. A charge / discharge test was performed using this lithium secondary battery.

  FIG. 7 is an electron microscope image of lithium manganate powder pyrolyzed at 750 ° C. It was confirmed that each particle was a porous particle and could be used as a positive electrode active material.

  FIG. 8 is an electron microscope image of lithium manganate powder pyrolyzed at 900 ° C. Each particle was confirmed to be a porous particle, and was found to be usable as a positive electrode active material as in FIG.

  FIG. 9 is a powder X-ray diffraction pattern of the lithium manganate powder produced at 750 ° C. The vertical axis represents the diffraction intensity, and the horizontal axis represents the Bragg angle 2θ. The solid line is a sample obtained by the conventional external combustion type. The long broken line and the short broken line are samples obtained by the internal combustion type of the present invention. The long dashed line is a sample obtained by firing at 750 ° C. and under a nitrogen gas atmosphere. The short dashed line is a sample obtained by firing at 750 ° C. and in an air atmosphere. The letters “Calcined” (700 ° C. · 2 h) mean that powder is produced by firing and then re-baked at 700 ° C. for 2 hours. The letter “As-prepared” (generated powder) means that no re-firing is performed.

  It was found that the external combustion method includes an impurity peak and is not preferable as a positive electrode active material. In the internal combustion system of the present invention, since there is no impurity peak, it can be seen that impurities are hardly contained. Further, in the present invention, the peak height was low before re-baking (As-prepared: generated powder), but it was found that when re-baking, the peak increased rapidly and crystallization progressed. Furthermore, it has been found that the desired crystallization is promoted in both an air atmosphere and a nitrogen atmosphere.

FIG. 10 is a charge / discharge characteristic diagram of the lithium secondary battery composed of the 750 ° C. · N ₂ lithium manganate powder in FIG. The left figure shows the discharge curve, and the right figure shows the cycle characteristics. The vertical axis of the discharge curve is the output voltage (Voltage), the horizontal axis is the specific discharge capacity per gram, and its unit is mAh / g. The vertical axis of the cycle characteristics is the specific discharge capacity, and the horizontal axis is the cycle number.

  A broken line is a lithium secondary battery manufactured by the external combustion system, and a solid line is a lithium secondary battery manufactured by the internal combustion system of the present invention. 1C represents an operation curve of a reference electric load, and 4C represents an operation curve of a load four times the reference load. When the external combustion system and the internal combustion system are compared at 1C, there is not much difference. Although the characteristics are slightly deteriorated at an excessive load of 4C, the tendency of the characteristics to decrease at an excessive load is a property common to all lithium secondary batteries, and the lithium secondary battery of the present invention has reached a level that can withstand practical use. It was proved that.

  FIG. 11 is a charge / discharge characteristic diagram of the lithium secondary battery composed of the lithium manganate powder at 750 ° C./air in FIG. Details are the same as those in FIG. 10 and are omitted, and only different portions will be described. 7C shows an operation curve of a load seven times the reference load. Although the characteristics are slightly deteriorated even at an excessive load of 7C, there is no problem for the reason described above. Therefore, it was demonstrated that the lithium secondary battery of the present invention has reached a level that can withstand practical use.

  FIG. 12 is a powder X-ray diffraction pattern of the lithium manganate powder produced at 900 ° C. The vertical axis represents the diffraction intensity, and the horizontal axis represents the Bragg angle 2θ. The solid line is a sample obtained by the conventional external combustion type. A broken line is a sample obtained by the internal combustion type of the present invention, and is a sample obtained by firing at 900 ° C. and in an atmospheric atmosphere. The letters “Calcined” (900 ° C. · 2 h) mean that powder is produced by firing and then re-fired at 700 ° C. for 2 hours. The letter “As-prepared” (generated powder) means that no re-firing is performed.

  It was found that the external combustion method includes an impurity peak and is not preferable as a positive electrode active material. In the internal combustion system of the present invention, since there is no impurity peak, it can be seen that impurities are hardly contained. Further, in the present invention, the peak height was low before re-baking (As-prepared: generated powder), but it was found that when re-baking, the peak increased rapidly and crystallization progressed. Furthermore, it has been found that the desired crystallization is promoted in an air atmosphere.

  FIG. 13 is a charge / discharge characteristic diagram of a lithium secondary battery composed of the lithium manganate powder of FIG. The left figure shows the discharge curve, and the right figure shows the cycle characteristics. The vertical axis of the discharge curve is the output voltage (Voltage), the horizontal axis is the specific discharge capacity per gram, and its unit is mAh / g. The vertical axis of the cycle characteristics is the specific discharge capacity, and the horizontal axis is the cycle number.

  A solid line is a lithium secondary battery manufactured by the internal combustion system of the present invention. 1C represents an operation curve of a reference electric load, 4C represents an operation curve of a four times load of the reference load, 7C represents an operation curve of a seven times load of the reference load, and 9C represents an operation curve of a nine times load of the reference load. Compared to the thermal decomposition temperature of 750 ° C., the thermal decomposition temperature of 900 ° C. has a smaller difference in both the discharge curve and the cycle characteristic curve compared to the reference load operation curve of 1C. Therefore, it was demonstrated that the lithium secondary battery of the present invention can be sufficiently used even in charge / discharge under an excessive load.

  FIG. 14 is a specification table of electrodes formed from the lithium manganate powder produced in Example 1. The lithium manganate powder of the present invention was used for the positive electrode, carbon fine powder was used as the conductive material, and PVDF (polyvinylidene fluoride) was used as the binder. The negative electrode is artificial graphite.

  The specifications of the single cell are as shown in FIG. This specification is an electrode and cell specification mounted on an electric bicycle. It is also possible to use this cell for an electric vehicle. An electrode according to this specification was prepared, and the actual specification characteristics of the lithium manganate powder of the present invention were tested. If data that passes this actual test is obtained, the present invention can provide a breakthrough technology to a lithium secondary battery.

  FIG. 15 is a specification table of an electric bicycle battery manufactured using the electrodes obtained in FIG. The design electric capacity is 5.4 Ah, the average voltage is 34.2 V, the operating voltage is 30 to 37.8 V, the module weight is 3 kg, the module size is 285 × 180 × 65 mm, and the weight energy density is 61.5 Wh / kg.

  FIG. 16 is an initial characteristic table of 10 single cells. Of these, nine single cells are connected in series to produce one electric vehicle battery. Ten single cells, D1 to D10, were prepared, and the initial capacity (Ah), DC resistance (mΩ), and AC impedance (mΩ) were measured for each. It was proved that the initial capacity did not change so much at 0.2 C load and 1 C load, and did not deviate so much from the design capacity of 5.4 Ah. The DC resistance and AC impedance were also very small for 10 types, indicating that mass production of single-cell and electric vehicle batteries with stable quality was possible.

  FIG. 17 is an output characteristic diagram of a single cell fabricated from the present invention. Output characteristics were measured for 0.2C (light load) to 30C (excessive load) with 1C as a reference load. The change in output characteristics was small from 0.2C to 10C, and it was proved that the single cell of the present invention had quality stability.

  FIG. 18 is a comparison diagram of output characteristics of a single cell between the present invention and a conventional solid phase method. The vertical axis represents the discharge capacity, and the horizontal axis represents the discharge load. In the conventional solid phase method, when the discharge load increases, the discharge capacity rapidly decreases. On the other hand, with the flame spray method of the present invention, it has been demonstrated that the discharge capacity slowly decreases even when the discharge load increases, and the battery characteristics that can cope with an excessive load are exhibited.

  FIG. 19 is an output characteristic diagram of an electric bicycle battery using nine single cells. The vertical axis is the output voltage, and the horizontal axis is the electric capacity. Even if the electric capacity is increased, the output voltage hardly changes. Further, even if the electric load is changed in the range of 0.2 to 5C, the output characteristics hardly change. Therefore, a lithium manganate secondary battery suitable as an electric vehicle battery can be realized.

  The present invention is not limited to the above-described embodiments and examples, and an additive is added to lithium manganate, for example, manganese / nickelate lithium or manganese / nickel / cobaltate lithium is also included. Further, it goes without saying that various modifications and design changes are included in the technical scope without departing from the technical idea of the present invention.

  The lithium manganate powder according to the present invention can be used as a positive electrode material of a lithium secondary battery, and an electrode and a lithium secondary battery can be provided by using this. This lithium secondary battery can be used as a mobile phone, a notebook computer, a camera-integrated video, a battery for a bicycle, a battery for an electric vehicle, a battery for a portable device, and other secondary batteries for general use.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the powder manufacturing apparatus 1 which implement | achieves 1st Embodiment of the manufacturing method of the lithium manganate powder concerning this invention. FIG. 4 is a simplified cross-sectional view of a reaction unit 23 at a burner position. It is explanatory drawing which showed the change process by baking of the raw material mist M. FIG. It is a schematic block diagram of the powder manufacturing apparatus 1 which implement | achieves 2nd Embodiment of the manufacturing method of the lithium manganate powder which concerns on this invention. It is a schematic block diagram of the powder manufacturing apparatus 1 which implement | achieves 2nd Embodiment of the manufacturing method of the lithium manganate powder which concerns on this invention. It is a crystal structure figure of lithium manganate. It is an electron microscope image of the lithium manganate powder pyrolyzed and produced at 750 degreeC. It is an electron microscope image of the lithium manganate powder pyrolyzed and produced at 900 degreeC. It is a powder X-ray diffraction pattern of the lithium manganate powder produced | generated at 750 degreeC. FIG. 10 is a charge / discharge characteristic diagram of a lithium secondary battery composed of 750 ° C. · N ₂ lithium manganate powder in FIG. 9. FIG. 10 is a charge / discharge characteristic diagram of a lithium secondary battery composed of 750 ° C./air lithium manganate powder in FIG. 9. It is a powder X-ray diffraction pattern of the lithium manganate powder produced | generated at 900 degreeC. It is a charging / discharging characteristic view of the lithium secondary battery comprised from the lithium manganate powder of FIG. 4 is a specification table of electrodes formed from lithium manganate powder produced in Example 1. It is a specification table | surface of the battery for electric vehicles produced using the electrode obtained in FIG. It is an initial characteristic table | surface of ten single cells. It is an output characteristic figure of the single cell produced from this invention. It is an output characteristic comparison figure of the single cell of this invention and the conventional solid-phase method. It is an output characteristic figure of the battery for electric vehicles using ten single cells. It is sectional drawing of the cylindrical reaction part by the internal combustion system shown by patent document 1 (USP3,230,064). It is AA sectional view taken on the line of FIG. It is a longitudinal cross-sectional view of the reactor by the external combustion system shown by patent document 2 (Japanese Patent Publication No. 5-75685).

Explanation of symbols

1 Powder production equipment 11 Tubular reaction section
DESCRIPTION OF SYMBOLS 12 Powder separation part 13 Suction machine 14 Duct 15 Duct 21 Raw material mist supply part 22 Raw material mist storage part 23 Reaction part 24 Recovery member 31 Introduction pipe 32 Two-fluid nozzle 41 Burner 42 Cooling gas supply means 43 Filter 43a Opening part 44 Firing space DESCRIPTION OF SYMBOLS 100 Cylindrical reaction part 101 Piping 102 Powder raw material ejection part 103 Torch burner 104 Spray nozzle 105 Cylindrical reaction part 106 Powder raw material supply part 107 Heater 108 Cooling part 109 Powder delivery device F Flame swirl flow G Carrier gas L Interval M Raw material mist S Raw material solution W Interval

Claims (10)

In a method for producing lithium manganate powder, which is an electrode material for a lithium secondary battery, a flame is formed in each of a plurality of axially-separated cross sections that are axially separated in a cylindrical reaction portion that produces lithium manganate powder. the swirling flow is formed, the tubular below the reaction section provided material mist reservoir for storing the material mist containing at least the material of the lithium manganate powder, supplying the material mist upward from the material mist reservoir The raw material mist is introduced into the plurality of flame swirl flows to swirl the raw material mist, and the raw material mist is pyrolyzed by the flame during the swirling to form lithium manganate powder. Method for producing lithium manganate powder. The said raw material mist is a manufacturing method of the lithium manganate powder of Claim 1 which mix | blended the additive with the raw material of the lithium manganate powder. The method for producing lithium manganate powder according to claim 1, wherein the flame swirl is swirled along the inner surface of the cylindrical reaction section. The manufacturing method according to claim 1, 2 or 3, wherein a filter that allows the raw material mist to pass through is disposed above the raw material mist reservoir. The method for producing a lithium manganate powder according to claim 4, wherein the raw material solution is sprayed in a horizontal direction with respect to the raw material mist storage part to form a raw material mist, and the raw material mist is retained in the raw material mist storage part. The raw material mist is sucked and raised from the raw material mist storage part by suction means provided outside the cylindrical reaction part, and the lithium manganate powder generated from the raw material mist in the flame swirl flow is brought out of the cylindrical reaction part. The method for producing a lithium manganate powder according to claim 5, wherein the lithium manganate powder is derived and separated from the exhaust gas and collected. A method for producing a lithium manganate powder, comprising re-firing the lithium manganate powder produced by the production method according to claim 1. A lithium manganate powder produced by the production method according to claim 1. An electrode for a lithium secondary battery, wherein the electrode is formed from the lithium manganate powder produced by the production method according to claim 1. An lithium secondary battery comprising an electrode formed from the lithium manganate powder produced by the production method according to claim 1 as a positive electrode.

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