TWI468367B - Production method of positive electrode active material for lithium ion battery and positive electrode active material for lithium ion battery - Google Patents

Description

Method for producing positive electrode active material for lithium ion battery and positive electrode active material for lithium ion battery

The present invention relates to a method for producing a positive electrode active material for a lithium ion battery and a positive electrode active material for a lithium ion battery.

A lithium transition metal composite oxide is known as a positive electrode active material for a lithium ion battery. For example, as described in Patent Document 1, a lithium transition metal composite oxide is produced by mixing a lithium compound and a transition metal compound to prepare a positive electrode active material precursor for a lithium ion battery, followed by firing. Make it composite.

For its long-term use, lithium-ion batteries require various characteristics such as cycle characteristics and storage characteristics for repeated charging and discharging, and are increasingly required to be highly capacitive at an extremely high level. In addition, with the expansion of demand for consumer devices such as mobile phones and personal computers or lithium batteries for vehicles, it is required to manufacture lithium ion batteries at low cost and efficiently.

In the manufacturing step of such a lithium ion battery, the step of calcining and compounding the positive electrode active material precursor for a lithium ion battery as described above is required. In the firing step, the following method is generally used: The firing container filled with the precursor is placed in a firing furnace (resting furnace) and heated by a conveyor belt method or a batch method. When the firing is performed in a static furnace as described above, a large amount of the precursor can be efficiently fired by sequentially feeding the firing container filled with the plurality of precursors into the furnace.

Patent Document 1: Japanese Patent No. 3334179

However, the positive electrode active material precursor for a lithium ion battery before firing contains a large amount of gas or moisture such as carbon dioxide or nitrogen oxide. Therefore, when the firing is started in the stationary furnace, gas or moisture is initially released. Therefore, even if the precursor is sufficiently filled in the firing container, the compound which is actually compounded by firing is only the portion remaining from the gas or moisture which is previously discharged into the firing container. The remaining portion is actually only about 45 to 50% of the precursor to be filled, which is problematic from the viewpoint of efficiently manufacturing a lithium ion battery.

Further, when firing in a static furnace, it is difficult to uniformly heat the precursor to be filled in the firing container, and the unevenness of firing occurs, and the characteristics of the lithium transition metal composite oxide which is formed are deviated. The problem.

Therefore, an object of the present invention is to provide a method for producing a high-quality positive electrode active material for a lithium ion battery at low cost.

The inventors of the present invention conducted intensive studies and found that in the firing step of the positive electrode active material precursor for a lithium ion battery, the rotary kiln is used to pre-fire the initial stage of releasing the gas or water, and the gas is sufficiently released. Alternatively, the moisture precursor is subjected to main firing to be composited, whereby the production efficiency is improved. Further, in the case of the main firing, the precursor is uniformly fired by using a rotary kiln, and a high-quality positive electrode active material for a lithium ion battery can be obtained.

The present invention, which is based on the above findings, is a method for producing a positive electrode active material for a lithium ion battery, which comprises the steps of using a rotary kiln as a lithium carbonate containing a precursor of a positive electrode active material for a lithium ion battery. The salt is pre-baked, whereby the mass % of the total metal in the lithium-containing carbonate is increased by 1 to 105% before the pre-baking, and then the main baking is performed using a rotary kiln.

In one embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, the increase ratio of the mass % of the total metal in the lithium-containing carbonate to be calcined is 50 to 97%.

In another embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, calcination is carried out at 200 to 1200 ° C for 30 to 120 minutes.

In still another embodiment, the method for producing a positive electrode active material for a lithium ion battery according to the present invention is carried out at 500 to 900 ° C for 0.5 to 12 hours at a temperature of 700 to 1200 ° C for a first main baking step. The second main firing step in 24 hours and the third main firing step in 0.5 to 12 hours at 400 to 700 ° C are used for the main firing.

In still another embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, the first to third main firing steps are performed using at least two or more rotary kiln.

In still another embodiment of the method for producing a positive electrode active material for a lithium ion battery according to the present invention, the positive electrode active material has a composition formula: Li _x Ni _1-y M _y O _2+α (in the above formula, M is selected From Sc, Ti, V, Cr. One or more of Mn, Fe, Co, Cu, Zn, Ga, Ge, Al, Bi, Sn, Mg, Ca, B, and Zr, and 0.9≦x≦1.2,0 <y≦0.7, 0.05≦α).

In still another embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, M is selected from one or more selected from the group consisting of Mn and Co.

In another aspect, the present invention is a positive electrode active material for a lithium ion battery, which is of a composition formula: Li _x Ni _1-y M _y O _2+α (in the above formula, M is selected from the group consisting of Sc, Ti One or more of V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Al, Bi, Sn, Mg, Ca, B, and Zr, and 0.9≦x≦1.2,0<y≦0.7 , 0.05 ≦ α), and the knock tightness is 1.8 to 2.2 g/cc.

In one embodiment, the positive electrode active material for a lithium ion battery of the present invention is one or more selected from the group consisting of Mn and Co.

According to the present invention, it is possible to provide a method for producing a high-quality positive electrode active material for a lithium ion battery at low cost.

(Composition of positive active material for lithium ion battery)

The material of the positive electrode active material for a lithium ion battery produced in the present invention can be widely used as a compound for a positive electrode active material for a positive electrode for a lithium ion battery, and it is particularly preferable to use lithium cobaltate (LiCoO ₂ ). A lithium-containing transition metal oxide such as lithium nickelate (LiNiO ₂ ) or lithium manganate (LiMn ₂ O ₄ ). The positive electrode active material for a lithium ion battery produced by using such a material is, for example, a composition formula: Li _x Ni _1-y M _y O _2+α (in the above formula, M is selected from the group consisting of Sc, Ti, V, Cr, One or more of Mn, Fe, Co, Cu, Zn, Ga, Ge, Al, Bi, Sn, Mg, Ca, B, and Zr, and 0.9≦x≦1.2, 0<y≦0.7, 0.05≦α) Said.

The ratio of lithium to the total metal in the positive electrode active material for a lithium ion battery is 0.9 to 1.2 because the crystal structure is not easily maintained when it is less than 0.9, and the capacitance is lowered when it exceeds 1.2.

The oxygen of the positive electrode active material for a lithium ion battery of the present invention is represented by O _{2+ α} (0.05 ≦ α) as described above, and in the case of containing an excessive amount of oxygen and used in a lithium ion battery, the capacitance, Battery characteristics such as ratio characteristics and capacitance retention rate are improved. Here, with respect to α, α is preferably 0.15, more preferably α>0.20, and typically 0.05≦α≦0.25.

Moreover, in the composition formula, the positive electrode active material for a lithium ion battery of the present invention is preferably one or more selected from the group consisting of Mn and Co.

Further, the positive electrode active material for a lithium ion battery of the present invention has a knocking degree of 1.8 to 2.2 g/cc, and when used in a lithium ion battery, battery characteristics such as capacitance, ratio characteristics, and capacity retention are improved. Previously, when the lithium-containing carbonate as a precursor was fired only by a static furnace, the particles of the precursor were evacuated from each other, so that the tapping degree was not easily improved. In the present invention, the lithium-containing carbonate as a precursor is flowed while being rotated by a rotary kiln, and the particles are granulated and heavyned to increase the knocking degree.

(Method for producing positive electrode active material for lithium ion battery)

Next, a method for producing a positive electrode active material for a lithium ion battery according to an embodiment of the present invention will be described in detail.

First, a metal salt solution is prepared. The metal is Ni and one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Al, Bi, Sn, Mg, Ca, B, and Zr. Further, the metal salt is a sulfate, a chloride, a nitrate, an acetate or the like, and particularly preferably a nitrate. The reason for this is that even if it is mixed as an impurity into the calcined raw material, it can be directly calcined. Therefore, the washing step is omitted, and the nitrate functions as an oxidizing agent, and has a function of promoting oxidation of the metal in the calcining raw material. Each metal contained in the metal salt is previously adjusted to a desired molar ratio. Thereby, the molar ratio of each metal in the positive electrode active material is determined.

Then, lithium carbonate was suspended in pure water, and thereafter a metal salt solution of the above metal was introduced to prepare a lithium salt solution slurry. At this time, lithium carbonate containing fine particles is precipitated in the slurry. In the case of heat treatment of a sulfate or a metal salt as a metal salt, when the lithium compound is not reacted, it is washed with a saturated lithium carbonate solution, and then separated by filtration. In the case where a lithium compound is reacted as a lithium raw material during heat treatment such as nitrate or acetate, it can be directly separated by filtration without being washed, and dried, whereby it can be used as a firing precursor.

Then, by drying the filtered lithium-containing carbonate, a lithium salt composite (precursor for a lithium ion battery positive electrode material) powder is obtained. In the precursor for a positive electrode material for a lithium ion battery, lithium, nickel, manganese, cobalt, or the like in a total amount of 20 to 40% by mass is contained as a metal.

(pre-burning step)

Then, the firing device 20 shown in Fig. 1 is prepared. The firing device 20 includes a rotary kiln 10, a powder input unit 11, a gas supply unit 12, a filter bag 13, and a powder discharge unit 14.

The rotary kiln 10 is provided with a core tube 17, and an outer cylinder 15 is formed so as to surround the core tube 17, and a heater 16 provided on the outer side of the outer cylinder 15 and heating the core tube 17 is formed. The core tube 17 is formed into a specific inner diameter and length depending on the amount of the pre-fired precursor, the pre-baking time, and the like. For example, an inner diameter of 125 to 3500 mm and a total length of 1 to 30 m can be used. In the core tube 17, a stirring blade (not shown) for stirring the powder of the pre-fired object can be formed so as to rise from the inner wall of the furnace core tube 17. The core tube 17 is preferably formed of a material that satisfactorily transfers heat from the heater 16 and does not generate contaminants that are mixed into the precursor, and may be formed, for example, of Ni, Ti, stainless steel, or ceramic. The outer cylinder 15 is also preferably formed of a material that transfers heat from the heater 16 well, such as Ni, Ti, stainless steel or ceramic. The heater 16 is not particularly limited as long as it is located on the outer side of the outer cylinder 15. Further, in Fig. 1, the heater 16 is provided at one location, but may be provided at a plurality of locations. The rotary kiln 10 is inclined so as to descend from the front end portion toward the rear end portion so as to be moved rearward from the front end portion into the front surface. The inclination angle is not particularly limited, and can be set according to the pre-baking time or the like.

The powder input unit 11 is provided with a precursor to be pre-fired inside. The powder input portion 11 is provided at the front end portion of the rotary kiln 10, from which the precursor is introduced.

The powder discharge portion 14 is provided at the rear end portion of the rotary kiln 10. The powder (pre-fired body) which has been pre-fired through the core tube 17 is discharged from the powder discharge portion 14.

The gas supply unit 12 supplies the gas circulated in the firing device 20 . An inert gas such as nitrogen or argon, oxygen, or the like is supplied from the gas supply unit 12. The path indicated by the arrow of FIG. 1 is a circulation path of the gas supplied from the gas supply unit 12.

The filter bag 13 is disposed at the front end of the rotary kiln 10. The filter bag 13 recovers the precursors during the exhaust process. The filter bag 13 is formed by using a woven fabric or a non-woven fabric as a filter material and superimposing the filter material in a cylindrical shape.

As a pre-baking step, first, heating by the heater 16 is started while the core tube 17 is rotated. Here, the inclination angle and the rotation speed of the core tube 17 are appropriately set in accordance with the calcination time and the calcination temperature of the calcination for the mass of the precursor for the lithium ion battery positive electrode material to be charged later. For example, when the mass of the precursor is 20 to 110 g, the pre-baking time is 30 to 120 minutes, and the pre-baking temperature is 200 to 1200 ° C, the inclination angle of the core tube 17 can be set to 8 to 15°, and the rotation speed can be set to 3.6 to 9.6 radians/second.

Then, the temperature of the inside of the furnace core tube 17 is raised to 200 to 1200 ° C, and the precursor for the positive electrode material for lithium ion battery is supplied from the powder input portion 11 to the front end portion of the core tube 17. The precursor for the positive electrode material of the lithium ion battery to be charged is transferred and heated to the end portion of the core tube 17 while being stirred and heated in the rotating core tube 17. The pre-firing of the precursor is carried out in this manner. During the period, a gas or water such as carbon dioxide or nitrogen oxide is released from the precursor of the positive electrode material for the lithium ion battery, so that the mass % of the total metal in the precursor is increased by 1 to 105%, preferably higher, than before calcination. 50 to 97%. Further, during the pre-baking, the filter bag 13 collects and mixes the powder into the supply gas and discharges the powder such as the precursor from the core tube 17. The precursor is recovered by the filter bag 13 and can be reused as a raw material after purification.

Then, the pre-fired precursor is discharged from the powder discharge unit 14 to the outside of the apparatus, and then the following main firing is performed.

(formal firing step)

In the present invention, the main baking step is carried out by using a rotary kiln without using a baking furnace (stationary furnace). Therefore, in the firing process using the firing furnace, there is no occurrence of unevenness in firing of the precursor before filling into the firing vessel and heating. Therefore, a high-quality positive electrode active material for a lithium ion battery can be obtained.

Further, the main firing can be carried out stepwise in accordance with the function of increasing the density of the positive electrode active material or the function of adjusting the crystallinity. Each of these stages can be carried out using a rotary kiln or a plurality of rotary kiln.

A case where the main firing is performed by one rotary kiln will be described. For the rotary kiln for the main firing, a rotary kiln having the same configuration as that shown in Fig. 1 can be used. The arrangement of the rotary kiln used in the pre-baking and the rotary kiln used in the main firing is not particularly limited, and for example, it can be set as shown in FIG. 2 . In Fig. 2, the arrowed lines respectively indicate the rotary kiln.

In the form shown in Fig. 2(a), the rotary kiln 31 that is normally fired is such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in substantially the same direction. And set it up.

In the form shown in Fig. 2(b), the rotary kiln 32 that is formally fired is such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in substantially opposite directions. And set it up.

In the main firing step, heating of the heater is started while rotating the core tube of the rotary kiln 31, 32. Heating may be performed stepwise according to functions such as a function of increasing the density of the positive electrode active material or a function of adjusting the crystallinity. By heating the main firing stepwise in accordance with the function, a higher-quality positive electrode active material for a lithium ion battery can be produced. In order to perform the stepwise heating by the one rotary kiln 31, 32, a plurality of heaters are disposed at a predetermined interval from the front end portion to the rear end portion of the rotary kiln 31, 32. For example, the main firing step is divided into a first main baking step for forming a layered rock salt type crystal structure and a knocking tightness of the positive electrode active material, and a second main baking step for baking the positive electrode active material. In the case of the third main firing step for cooling, the heating is performed by changing the temperature of each of the ranges from the front end portion to the rear end portion of the rotary kiln 31, 32 into three portions. In this case, the conditions of each of the main calcination steps may be carried out at 700 to 1200 ° C for the first to first firing step at 0.5 to 12 hours, and at 500 to 900 ° C for the second to second firing step at 0.5 to 24 hours. The third main firing step is carried out at -700 ° C for 0.5 to 12 hours.

Further, the inclination angle and the rotation speed of the core tube of the rotary kiln 31 and 32 are appropriately set depending on the mass of the pre-fired body or the firing time of the main firing. For example, when the mass of the calcined body is 20 to 110 g and the main firing time is 1.5 to 48 hours, the inclination angle of the core tube can be set to 2 to 10°, and the rotation speed can be set. It is 3.6 to 9.6 radians/second.

After the start of the heating, the temperature in the core tube is raised to 700 to 1200 ° C, and the pre-fired body discharged from the rotary kiln 10 is supplied from the powder input portion to the front end portion of the furnace core tube. The pre-fired body to be charged is transferred to the end portion of the core tube while being stirred and heated in a rotating core tube, and is thus officially fired.

Then, the powder of the positive electrode active material is obtained by discharging the powder which has been formally fired from the powder discharge portion and pulverizing the powder. Since the obtained positive electrode active material uses a rotary kiln in the baking step, uneven baking is suppressed.

Next, the case where the main rotary baking is performed by two rotary kiln is demonstrated. For the rotary kiln for the main firing, a rotary kiln having the same configuration as that shown in Fig. 1 can be used. The arrangement of the rotary kiln used in the pre-firing and the rotary kiln used in the main firing is not particularly limited, and for example, it can be set as shown in FIG. In Fig. 3, the arrowed lines respectively indicate the rotary kiln.

In the form shown in Fig. 3 (a), the first rotary kiln 41 that is normally fired is located below the powder discharge portion of the pre-fired rotary kiln 10 and is inclined in substantially the same direction. Set it up in the way. In addition, the second rotary kiln 42 that is to be fired is disposed such that the powder input portion is located below the powder discharge portion of the first rotary kiln 41 that is actually fired, and is inclined in substantially the same direction.

In the form shown in Fig. 3 (b), the first rotary kiln 43 that is formally fired is such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in a substantially opposite direction. Configure it in a way. In addition, the second rotary kiln 44 that is to be fired is disposed such that the powder input portion is located below the powder discharge portion of the first rotary kiln 43 that is actually fired, and is inclined in a substantially opposite direction.

In the form shown in Fig. 3(c), the first rotary kiln 45 that is formally fired is such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in substantially opposite directions. Configure it in a way. In addition, the second rotary kiln 46 that is to be fired is disposed such that the powder input portion is located below the powder discharge portion of the first rotary kiln 45 that is normally fired, and is inclined in substantially the same direction.

In the form shown in Fig. 3 (d), the first rotary kiln 47 that is normally fired is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in substantially the same direction. Configure it in a way. In addition, the second rotary kiln 48 that is to be fired is disposed such that the powder input portion is located below the powder discharge portion of the first rotary kiln 47 that is actually fired, and is inclined in a substantially opposite direction.

In the form shown in FIG. 3(e), the first rotary kiln 49 that is to be fired is provided such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10. In addition, the second rotary kiln 50 that is formally fired is provided such that the powder input portion is located below the powder discharge portion of the first rotary kiln 49 that is actually fired. Further, the calcined kiln 10 and the first rotary kiln 49 and the second rotary kiln 50 that are to be fired are arranged in a substantially triangular shape when viewed from above, and are arranged to be inclined downward.

In the main firing step, first, the furnace core tubes of the first and second rotary kiln 41 to 50 which are actually fired are rotated, and heating by the heater is started. The heating is carried out stepwise in accordance with functions such as a function of increasing the density of the positive electrode active material or a function of adjusting the crystallinity. By heating the main firing stepwise in accordance with the function, a higher-quality positive electrode active material for a lithium ion battery can be produced. In order to perform the stepwise heating by the first and second rotary kilnes 41 to 50, a plurality of heaters are disposed at predetermined intervals from the end portions of the first and/or second rotary kiln 41 to 50 to the rear end portion. For example, the main firing step is divided into a first main baking step for forming a layered rock salt type crystal structure and a knocking tightness of the positive electrode active material, and a second main baking step for baking the positive electrode active material. And in the case of the third main firing step for cooling, the first and second firing steps are performed in the first rotary kiln 41, 43, 45, 47, and 49, and in the second rotary kiln 42, 44, The third firing step is carried out in 46, 48 and 50. The first firing step is performed in the first rotary kiln 41, 43, 45, 47, and 49, and the second and third firing steps are performed in the second rotary kiln 42, 44, 46, 48, and 50. In each of the ranges from the end portion to the rear end portion of the first and/or second rotary kiln 41 to 50 which are formally fired, the temperature is changed by the respective heaters to perform heating. In this case, the conditions of each of the main calcination steps may be carried out at 700 to 1200 ° C for the first to first firing step at 0.5 to 12 hours, and at 500 to 900 ° C for the second to second firing step at 0.5 to 24 hours. The third main firing step is carried out at -700 ° C for 0.5 to 12 hours.

In addition, the inclination angle and the rotational speed of the core tube of the first and second rotary kiln 41 to 50 that are formally fired are appropriately set depending on the mass of the pre-fired body or the firing time of the main firing. For example, when the mass of the calcined body is 20 to 110 g and the main firing time is 1.5 to 48 hours, the inclination angle of the core tube can be set to 2 to 10°, and the rotation speed can be set. It is 3.6 to 9.6 radians/second.

After the start of the heating, the pre-fired body discharged from the rotary kiln 10 is put into the powder from the first rotary kiln 41, 43, 45, 47 and 49 by the temperature in the core tube rising to 700 to 1200 °C. The part is put into the front end of the heart tube. The pre-fired body to be charged is transferred to the rear end portion of the core tube while being stirred and heated in the rotating core tube, and is discharged from the powder discharge portion. Then, the fired body discharged from the powder discharge portions of the first rotary kiln 41, 43, 45, 47, and 49 is supplied to the powder input portions of the second rotary kiln 42, 44, 46, 48, and 50 below. The fired body that has been introduced into the powder input portion of the second rotary kiln 42, 44, 46, 48, and 50 is then transferred to the rear end of the core tube while being stirred and heated in the rotating core tube, thereby completing It is officially fired and discharged from the powder discharge section.

Then, the powder which has been formally fired is discharged from the powder discharge portion, and the powder is pulverized, whereby a powder of the positive electrode active material is obtained. Since the obtained positive electrode active material uses a rotary kiln in the calcination step, uneven baking can be suppressed.

Next, a case where the main rotary firing is performed by using three rotary kiln will be described. For the rotary kiln used in the main firing, a rotary kiln having the same configuration as that shown in Fig. 1 can be used. The arrangement of the rotary kiln used in the pre-firing and the rotary kiln used in the main firing is not particularly limited, and for example, it can be set as shown in FIG. In Fig. 4, the arrowed lines respectively indicate the rotary kiln.

In the form shown in Fig. 4 (a), the first rotary kiln 61 that is normally fired is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in substantially the same direction. Set by way. In addition, the second rotary kiln 62 that is formally fired is disposed such that the powder input portion is located below the powder discharge portion of the first rotary kiln 61 and is inclined in substantially the same direction. Furthermore, the third rotary kiln 63 that is to be fired is disposed such that the powder input portion is located below the powder discharge portion of the second rotary kiln 62 and is inclined in substantially the same direction.

In the form shown in Fig. 4 (b), the first rotary kiln 64 that is formally fired is such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10, and is inclined in a substantially opposite direction. Set by way. In addition, the second rotary kiln 65 that is formally fired is provided such that the powder input portion is located below the powder discharge portion of the first rotary kiln 64 and is inclined in a substantially opposite direction. Further, the third rotary kiln 66 that is to be fired is disposed such that the powder input portion is located below the powder discharge portion of the second rotary kiln 65 and is inclined in a substantially opposite direction.

In the form shown in FIG. 3(c), the first rotary kiln 67 that is to be fired is provided such that the powder input portion is located below the powder discharge portion of the pre-fired rotary kiln 10. In addition, the second rotary kiln 68 that is formally fired is provided such that the powder input portion is located below the powder discharge portion of the first rotary kiln 67 that is actually fired. In addition, the third rotary kiln 69 that is formally fired is provided such that the powder input portion is located below the powder discharge portion of the second rotary kiln 68 that is actually fired. Further, the calcined kiln 10 and the first to third rotary kiln 67, 68, and 69 which are to be fired are formed in a substantially rectangular shape when viewed from above, and are arranged to be inclined downward.

In the main firing step, the furnace core tubes of the first to third rotary kiln 61 to 69 that are actually fired are first rotated, and heating by the heater is started. The heating is carried out stepwise in accordance with functions such as a function of increasing the density of the positive electrode active material or a function of adjusting the crystallinity. By heating the main firing stepwise in accordance with the function, a higher-quality positive electrode active material for a lithium ion battery can be produced. For example, the main firing step is divided into a first main baking step for forming a layered rock salt type crystal structure and a knocking tightness of the positive electrode active material, and a second main baking step for baking the positive electrode active material. In the case of the third main firing step for cooling, the first firing step is performed in the first rotary kiln 61, 64, and 67, and the second firing step is performed in the second rotary kiln 62, 65, and 68. The third baking step is performed in the third rotary kiln 63, 66, and 69. In this case, the conditions of each of the main calcination steps may be carried out at 700 to 1200 ° C for the first to first firing step at 0.5 to 12 hours, and at 500 to 900 ° C for the second to second firing step at 0.5 to 24 hours. The third main firing step is carried out at -700 ° C for 0.5 to 12 hours.

In addition, the inclination angle and the rotation speed of the core tube of the first to third rotary kiln 61 to 69 that are formally fired are appropriately set depending on the mass of the pre-fired body or the firing time of the main firing. For example, when the mass of the calcined body is 20 to 110 g and the main firing time is 1.5 to 48 hours, the inclination angle of the core tube can be set to 2 to 10°, and the rotation speed can be set to 3.6 to 9.6 radians/second.

After the start of the heating, the pre-fired body discharged from the rotary kiln 10 is introduced into the core from the powder input portion of the first rotary kiln 61, 64, 67 by the temperature in the core tube rising to 700 to 1200 °C. The front end of the tube. The pre-fired body to be charged is transferred to the rear end portion of the core tube while being stirred and heated in the rotating core tube, and is discharged from the powder discharge portion. Then, the fired body discharged from the powder discharge portions of the first rotary kiln 61, 64, and 67 is supplied to the powder input portions of the second rotary kiln 62, 65, and 68 below. The fired body that has been introduced into the powder input portion of the second rotary kiln 62, 65, and 68 is then transferred to the rear end portion of the core tube while being stirred and heated in the rotating core tube, thereby being discharged from the powder discharge portion. . Then, the fired body discharged from the powder discharge portions of the second rotary kiln 62, 65, and 68 is introduced into the powder input portions of the lower third rotary kiln 63, 66, and 69. The fired body that has been introduced into the powder input portion of the third rotary kiln 63, 66, and 69 is then transferred and heated to the rear end portion of the core tube while being stirred and heated in the rotating core tube, thereby completing the final firing. It is discharged from the powder discharge portion.

Then, the powder of the positive electrode active material is obtained by discharging the powder which has been officially fired from the powder discharge portion and pulverizing the powder. Since the obtained positive electrode active material uses a rotary kiln in the baking step, uneven baking is suppressed.

Further, in the above-described baking step, the pre-baking is performed in a different rotary kiln than in the main firing system, but it may be carried out using one rotary kiln. In this case, it is necessary to divide one rotary kiln into regions that distinguish heating conditions according to functions, and heat them to different firing temperatures by using different heaters. Further, in the above-described firing step, the firing is performed by one to three rotary kiln, but the present invention is not limited thereto, and four or more rotary kiln may be used.

When the main firing step is performed by one rotary kiln, and when the pre-firing and the main firing step are performed by one rotary kiln, since the number of rotary kiln is small, the working space is considered. Words have advantages. In other cases, when one rotary kiln is used for firing according to each function of the main firing step, since the heating conditions in one rotary kiln are the same, it is possible to perform firing by using a simple device. advantage.

[Examples]

The embodiments for better understanding of the invention and its advantages are provided below, but the invention is not limited to the embodiments.

(Examples 1 to 17)

First, the amount of lithium carbonate described in Table 1 was suspended in 3.2 liters of pure water, and then a 4.8 liter metal salt solution was charged. Here, the metal salt solution was adjusted to adjust the nitrate hydrate of each metal so that each metal had the composition ratio described in Table 1, and the total metal molar number was adjusted to 14 mol.

In addition, the amount of lithium carbonate suspended is the amount of the value of Table 1 when the product (the positive electrode active material of the lithium ion secondary battery, that is, the positive electrode active material) is Li _x Ni _1-y M _y O _2+α . And calculated by the following formula.

W(g)=73.9×14×(1+0.5X)×A

In the above formula, "A" is a value obtained by multiplying the amount of lithium of the lithium compound other than the lithium carbonate remaining in the filtered raw material in addition to the amount required for the precipitation reaction. For example, in the case of a nitrate salt or an acetate salt, when the lithium salt is reacted as a raw material for firing, "A" is 0.9, such as a sulfate or a chloride, and when the lithium salt is not reacted as a raw material for firing, "A" It is 1.0.

The lithium carbonate containing fine particles was precipitated in the solution by this treatment, but the precipitate was separated by filtration using a filter press.

Then, the precipitate was dried to obtain a lithium-containing carbonate (precursor for a positive electrode material for a lithium ion battery). Further, at this time, the concentration of the total metal in the precursor is 29 to 33% by mass.

Then, using a rotary kiln (heart tube: total length 2000 mm × inner diameter 250 mm) manufactured by Takasago Industries Co., Ltd., a pre-firing device as shown in Fig. 1 is prepared, thereby starting the circulation of oxygen from the gas supply unit in the system. The heater is heated and the rotary kiln is rotated at a rotational speed of 9.6 rad/sec. Set the tilt angle of the rotary kiln to 10°. When the temperature in the furnace core tube reaches 600 ° C, the precursor is supplied into the furnace core tube from the powder input portion while maintaining the temperature. The amount of the precursor was 110 g/min. Before being introduced into the core tube, the precursor is pre-fired by stirring and transferring in a rotating heart tube to release gas or moisture. Before the pre-firing, the precursor is discharged from the powder discharge portion to the outside of the device. The concentration of the total metal in the discharged precursor is 54 to 58% by mass.

Then, a firing apparatus of the form shown in Fig. 4 (a) is prepared. Each rotary kiln is a rotary kiln manufactured by Takasago Industrial Co., Ltd. (heart tube: total length 2000 mm × inner diameter 250 mm). First, while heating the gas from the gas supply unit in the system, the heating of the heater is started, and each rotary kiln is rotated at a rotation speed of 9.6 rad/sec. The inclination angle of each rotary kiln was set to 10°. When the temperature in the furnace core tube reaches 700 ° C, the precursor is supplied into the furnace core tube from the powder input portion while maintaining the temperature. The amount of the precursor was 110 g/min. The pre-firing is carried out by stirring and transferring in a rotating heart tube to be released into the core tube, thereby releasing gas or moisture. The powder is introduced into the powder input portion of the first rotary kiln which is officially fired from the powder discharge portion before the pre-firing. The concentration of the total metal in the discharged precursor is 31 to 63% by mass.

Then, the first main calcination step is carried out at 700 to 1200 ° C for 1 to 12 hours in the first rotary kiln, and then the second main calcination step is carried out at 500 to 900 ° C for 0.5 to 24 hours in the second rotary kiln. The third main firing step is carried out at 400 to 700 ° C for 3 to 10 hours in the third rotary kiln to perform main firing and obtain an oxide. Then, the obtained oxide is crushed to obtain a powder of a lithium ion secondary battery positive electrode material.

(Embodiment 18)

In Example 18, each metal of the raw material was set to the composition shown in Table 1, and the metal salt was used as a chloride, and the lithium carbonate was precipitated, and then washed with a saturated lithium carbonate solution and filtered, and then, The same treatments as in Examples 1 to 17 were carried out.

(Embodiment 19)

In Example 19, each metal of the raw material was set to the composition shown in Table 1, and the metal salt was used as a sulfate, and the lithium carbonate was precipitated, and then washed with a saturated lithium carbonate solution and filtered, and then, The same treatments as in Examples 1 to 17 were carried out.

(Comparative Examples 1 to 3)

In Comparative Examples 1 to 3, each metal of the raw material was set to have the composition shown in Table 1. Then, lithium-containing carbonates (precursors for lithium ion battery positive electrode materials) similar to those of Examples 1 to 17 were obtained. Then, a ceramic firing container having a length × width = 300 mm × 300 mm and a depth of 115 mm was prepared, and a lithium carbonate was filled in the firing container. Then, the baking container was placed in an air environment furnace (resting furnace), and firing by heating by a heater was started. The baking time is 6 to 12 hours, and the baking temperature is set to 700 to 1100 °C. In this manner, the sample in the firing vessel was heated and kept at a holding temperature of 700 to 1100 ° C for 2 hours, and then left to cool for 3 hours to obtain an oxide. Then, the obtained oxide is crushed to obtain a powder of a lithium ion secondary battery positive electrode material.

The metal content in each of the positive electrode materials was measured by an inductively coupled plasma emission spectrometer (ICP-OES) to calculate the composition ratio (mol ratio) of each metal. Further, the oxygen content was measured by the LECO method to calculate α. The results of confirming these are as described in Table 1.

The knockness was set to the density after 200 times of knocking.

The positive electrode material, the conductive material, and the binder are weighed at a ratio of 85:8:7, and the positive electrode material and the conductive material are mixed and dissolved in an organic solvent (N-methylpyrrolidone). The slurry was applied to an Al foil, and after drying, it was pressed to prepare a positive electrode. Then, a 2032 type coin battery in which the counter electrode was used for the evaluation of Li was prepared, and the electrolytic solution was prepared by dissolving 1 M-LiPF ₆ in EC-DMC (1:1), and measuring the discharge at a current density of 0.2 C. capacitance. Further, the ratio of the discharge capacitance at a current density of 2 C to the battery capacitance at a current density of 0.2 C was calculated to obtain a ratio characteristic. Further, the capacitance retention ratio was measured by comparing the initial discharge capacitance obtained by using the discharge current of 1 C at room temperature with the discharge capacitance after 100 cycles.

The test conditions and results are shown in Tables 1-3.

(Evaluation)

In all of Examples 1 to 19, excellent knocking properties and battery characteristics were exhibited.

In particular, the metal salts used as the raw materials of Examples 1 to 17 were nitrates, and thus exhibited better battery characteristics than Examples 18 and 19.

In Comparative Examples 1 to 3, only one shot was fired in a static furnace, and it was difficult to uniformly fire the precursor, so that the knocking degree and battery characteristics were inferior compared with the examples.

10. . . Pre-fired rotary kiln

11. . . Powder input department

12. . . Gas supply department

13. . . filter bag

14. . . Powder discharge

15. . . Outer tube

16. . . Heater

17. . . Heart tube

20. . . Burning device

31 to 32, 41 to 50, 61 to 69. . . Formally fired rotary kiln

Fig. 1 is a schematic view of a pre-firing device.

Fig. 2 is a schematic view showing a form of firing in the main firing of (a) to (b) using one rotary kiln.

Fig. 3 is a schematic view showing a firing form of the main firing of (a) to (e) using two rotary kiln.

Fig. 4 is a schematic view showing a firing form of the main firing of (a) to (c) using three rotary kiln.

10. . . Pre-fired rotary kiln

11. . . Powder input department

12. . . Gas supply department

13. . . filter bag

14. . . Powder discharge

15. . . Outer tube

16. . . Heater

17. . . Heart tube

20. . . Burning device

Claims (5)

A method for producing a positive electrode active material for a lithium ion battery, comprising the steps of: calcining a lithium carbonate as a precursor of a positive electrode active material for a lithium ion battery by a rotary kiln at 200 to 1200 ° C for 30 to 120 minutes; Therefore, the mass % of the total metal in the lithium-containing carbonate is increased by 1 to 105% before the pre-baking, and then the main firing is performed using a rotary kiln; wherein, the heating is performed at 700 to 1200 ° C for 0.5 to 12 hours. The main firing step is carried out by a main firing step, a second main firing step at 0.5 to 24 hours at 500 to 900 ° C, and a third main firing step at 0.5 to 12 hours at 400 to 700 ° C. The method for producing a positive electrode active material for a lithium ion battery according to the first aspect of the invention, wherein the increase ratio of the mass % of the total metal in the lithium-containing carbonate by the pre-baking is 50 to 97%. The method for producing a positive electrode active material for a lithium ion battery according to the first aspect of the invention, wherein the first to third main baking steps are performed using at least two or more rotary kiln. The method for producing a positive electrode active material for a lithium ion battery according to the first aspect of the invention, wherein the positive electrode active material is of a composition formula: Li _x Ni _1-y M _y O _2+α (in the formula, M system) One or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Al, Bi, Sn, Mg, Ca, B, and Zr, and 0.9 ≦ x ≦ 1.2, 0<y≦0.7, 0.05≦α). Positive electrode active material for lithium ion battery as claimed in item 4 of the patent application In the method of producing a quality, the M system is selected from one or more selected from the group consisting of Mn and Co.