JP6624631B2 - Lithium transition metal composite oxide and method for producing the same - Google Patents

Description

  The present invention relates to a lithium transition metal composite oxide as a positive electrode active material for a secondary battery, which suppresses a rise in resistance due to a high-temperature cycle and has a small decrease in discharge capacity and discharge voltage, and a method for producing the same.

  Lithium ion secondary batteries are excellent in terms of electromotive force and energy density, and are widely used as batteries for portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers. In recent years, attention has been paid not only to portable electronic devices but also to power sources for mobile and large-sized vehicles such as automobiles and power storage facilities, and developments in these fields have been actively promoted.

As a positive electrode active material for a lithium secondary battery, lithium cobalt oxide (LiCoO ₂ ) is widely used. However, cobalt, which is a main raw material, is expensive and supply insecurity due to depletion of resources has been pointed out. . On the other hand, the lithium transition metal composite oxide (chemical formula: Li _{1 + x} Ni _y Co _z Mn _1-x-y-z O ₂ ) uses a small amount of cobalt, and nickel and manganese as alternatives have relatively few resources. It is abundant and economically advantageous, and its potential is expected.

  However, when a lithium-transition metal composite oxide containing a large amount of nickel is used as the positive electrode active material, the crystal structure is unstable as compared with lithium cobalt oxide. I have.

  Various proposals have been made to solve such drawbacks.

For example, Patent Literature 1 discloses that a particle surface of a lithium transition metal composite oxide is made of aLi ₂ O—ZrO for the purpose of reducing interface resistance during charge and discharge and improving discharge capacity, rate characteristics, and cycle characteristics by the effect. ₂ coated with a coating material having a composition of (0.1 ≦ a ≦ 2.0): Li _1-x-y-z Ni _x Co _y Al _z O ₂ or Li _{1-x-y-z Ni x Co y Mn z O 2} (0 <x <1,0 <y <1,0 <z <1) lithium transition metal composite oxide represented by have been proposed.

In Patent Document 2, Li _x MO _y (M in the formula includes at least one of Co, Ni, Mn, Al, and Mg) as a positive electrode active material for a battery capable of improving cycle characteristics and aging life. It has been proposed to form zirconium oxide particles on the surface of a lithium-containing composite oxide by a mechanochemical method on a lithium transition metal composite oxide represented by the formula (1) to form a coating layer.

  Further, as means for coating the surface of the positive electrode active material with zirconium oxide, Patent Literature 3 discloses spraying a zirconia sol aqueous solution obtained by hydrolyzing and polymerizing zirconium isopropoxide on a composite oxide composed of lithium and a transition metal. There is proposed a method of coating with a method and performing a heat treatment.

  Patent Document 4 discloses that, by adding zirconium oxide, a part of the solid solution is dissolved in a transition metal as a main component, and the diffusion of Li in the crystal of the positive electrode active material is facilitated. It has been proposed that this be improved.

JP 2014-116149 A JP 2013-235666 A JP 2006-156032 A Japanese Patent No. 4766040

  The lithium transition metal composite oxide obtained by these production methods has both high charge capacity and high discharge capacity and improved cycle characteristics and output characteristics. However, in any of the documents, the zirconium compound to be added is expressed only by the name of the raw material used, and does not mention the particle form.

  The present invention has been made in view of the above-described problems, and suppresses a rise in resistance due to a high-temperature cycle of a secondary battery, and has a small decrease in discharge capacity and discharge voltage. An object is to provide a composite oxide and a method for producing the same. Another object of the present invention is to provide a method for producing a lithium transition metal composite oxide which is low in cost and excellent in mass productivity.

The present inventor has studied variously to solve the above-mentioned problems, and it has been found that mixing and firing zirconium oxide having a specific surface area of 30 to 90 m ² / g to a lithium transition metal composite oxide to attach a zirconium compound is secondary. The present inventors have found that the present invention is extremely effective in suppressing a rise in resistance due to a high-temperature cycle of a battery and suppressing a decrease in discharge capacity and discharge voltage, and completed the present invention.

  The gist of the present invention is as follows.

(1) chemical composition represented by the general formula _{Li 1 + x Ni y Co z} Mn 1-x-y-z-w M w O 2, wherein one M is selected from Al, Mg, W and Zr Or two or more metal elements, x is −0.05 ≦ x ≦ 0.05, y is 0.3 ≦ y <0.9, z is 0.05 ≦ z ≦ 0.35, and w is 0 Zirconium oxide having a specific surface area of 30 to 90 m ² / g is added to the surface of the particles of the lithium transition metal composite oxide in the range of ≦ w ≦ 0.1. A lithium transition metal composite oxide comprising a composite particle adhered by mass% and having a maximum particle diameter of 50 μm or less.

(2) Zirconium oxide having a specific surface area of 30 to 90 m ² / g is mixed with a lithium salt and a transition metal composite hydroxide simultaneously or sequentially in a dry manner, and then the calcination temperature is kept at 500 ° C or more and 700 ° C or less. The first baking step and the baking step are performed continuously without lowering the baking temperature from the first baking step, and the baking temperature is maintained at 700 ° C. or more and 1000 ° C. or less. The method for producing a lithium-transition metal composite oxide according to the above (1), wherein the temperature is once lowered to room temperature and then fired in a second firing step in which the firing temperature is kept at 700 ° C. or more and 1000 ° C. or less. Method.

(3) The addition amount of the zirconium oxide mixed with the lithium salt and the transition metal composite hydroxide simultaneously or sequentially is 0.1 to 1.0% by mass of the lithium transition metal composite oxide. The method for producing a lithium transition metal composite oxide according to the above (2).

(4) mixing said general formula _{Li 1 + x Ni y Co z} Mn 1-x-y-z-w M w O 2 expressed as a lithium transition metal composite oxides, the lithium salt and transition metal complex compound Here, simultaneously or sequentially, zirconium oxide particles having a specific surface area of 30 to 90 m ² / g are mixed, and the mixed powder is calcined, whereby zirconium oxide is attached to the surface of the lithium transition metal composite oxide. The method for producing a lithium transition metal composite oxide according to the above (2) or (3), wherein

According to the present invention, by depositing zirconium oxide having a specific surface area of 30 to 90 m ² / g on the surface of a lithium transition metal composite oxide, a charge / discharge cycle when the lithium transition metal composite oxide is placed in a high-temperature environment is obtained. This has the effect of suppressing the increase in resistance and suppressing the decrease in discharge capacity and discharge voltage. It is not clear why this effect can be obtained, but by attaching zirconium oxide fine powder having a large specific surface area to the lithium transition metal composite oxide, it is possible to suppress a change in the valency of Ni due to excessive insertion and extraction of lithium. In addition, it is presumed that the crystal structure is less likely to collapse, the resistance increase due to the discharge cycle is suppressed, and the decrease in the discharge capacity and discharge voltage is suppressed.

FIG. 3 is a diagram called a so-called Cole-Cole plot in which impedances of the coin-type lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 3 after cycle evaluation are measured and plotted on a complex plane. FIG. 11 is a diagram called a so-called Cole-Cole plot in which impedances of the coin-type lithium secondary batteries after the cycle evaluations of Examples 8 and 9 and Comparative Examples 6 and 7 are measured and plotted on a complex plane. FIG. 4 is a diagram comparing the average discharge voltage of each cycle in Examples 1 to 3 and Comparative Example 1 with respect to the discharge voltage maintenance ratio.

  Hereinafter, the present invention will be described in detail.

The inventors of the present invention have found that when zirconium oxide having a specific surface area of 30 to 90 m ² / g is attached to lithium transition metal composite oxide particles as a positive electrode active material for a secondary battery, the resistance of the secondary battery increases with high temperature cycling. , The reduction in discharge capacity and discharge voltage was suppressed, and it was found to be extremely effective. Thus, the present invention was completed.

Lithium transition metal complex oxide can be suitably used in the present invention, the chemical composition is represented by the general formula _{Li 1 + x Ni y Co z} Mn 1-x-y-z-w M w O 2, where, M Is one or more metal elements selected from Al, Mg, W and Zr, x is −0.05 ≦ x ≦ 0.05, y is 0.3 ≦ y <0.9, z Is a lithium transition metal composite oxide in the range of 0.05 ≦ z ≦ 0.35 and w is in the range of 0 ≦ w ≦ 0.1.

  In addition, the reason for setting -0.05 ≦ x ≦ 0.05 is that when x <−0.05, Ni in the Li layer increases, and the discharge capacity of the lithium transition metal composite oxide decreases. When x> 0.05, the excess Li enters the transition metal layer, increases the Ni valence, and causes a decrease in discharge capacity. Is a positive electrode material using a change in the valence of Ni, and the reason why 0.05 ≦ z ≦ 0.35 is that a necessary amount corresponding to the amount of Ni for stabilizing the crystal structure.

M in the lithium transition metal composite oxide Li _{1 + x} Ni _y Co _z Mn _1-x-y-z-w M _w O ₂ is selected as having an effect on improvement of high-temperature characteristics, and Al, Mg, W, and One or two or more metal elements selected from Zr, and w is preferably in a range of 0 ≦ w ≦ 0.1. When w ≧ 0.1, the discharge capacity decreases, which is not preferable.

The lithium transition metal composite oxide of the present invention is a composite particle in which 0.1 to 1.0% by mass of zirconium oxide having a specific surface area of 30 to 90 m ² / g adheres to the surface of the lithium transition metal composite oxide particle. And a maximum particle size of 50 μm or less.

To a specific surface area of the zirconium oxide and 30~90m 2 / ^g has a specific surface area of 30 m 2 / ^g less, small number of particles of zirconium oxide, since the contact surface with the lithium-transition metal composite oxide is reduced This makes uniform adhesion to the surface of the lithium transition metal composite oxide particles difficult. On the other hand, if it is larger than 90 m ² / g, zirconium oxides will aggregate before mixing with the transition metal composite compound or lithium salt, making it difficult to uniformly attach the lithium transition metal composite oxide to the particle surface. This is because The specific surface area of zirconium oxide was measured using Macsorb HM model-1208 manufactured by Mountech.

The reason why the composite particles to which 0.1 to 1.0% by mass of zirconium oxide is adhered is that when the amount of adhesion is smaller than 0.1% by mass, the secondary battery is accompanied by a charge / discharge cycle when the battery is placed in a high-temperature environment. No effect of suppressing a rise in resistance and suppressing a decrease in discharge capacity and discharge voltage is observed. The lower limit is set to 0.1% by mass, but more preferably 0.2% by mass or more. On the other hand, if the adhesion amount is larger than 1.0 mass%, that may arise from the problem of initial capacity and charge and discharge efficiency is lowered. And 0.1 to 1.0 mass% for it.

  Next, a method for producing the lithium transition metal composite oxide of the present invention will be described.

The method for producing a lithium transition metal composite oxide according to the present invention is such that a lithium transition metal composite oxide represented by the general formula Li _{1 + x} Ni _y Co _z Mn _1-x-y-z-w M _w O ₂ is obtained. , A lithium salt and a transition metal composite compound are mixed, and simultaneously or sequentially, zirconium oxide particles having a specific surface area of 30 to 90 m ² / g are dry-mixed, and then the calcination temperature is 500 ° C or higher and 700 ° C or lower. A first baking step, which is carried out without lowering the baking temperature from the first baking step, and a baking step, wherein the baking temperature is kept at 700 ° C. or more and 1000 ° C. or less. And a step of performing a second baking step in which the baking temperature is kept at 700 ° C. or more and 1000 ° C. or less after the baking temperature is once lowered to room temperature from the baking step.

To the general formula _{Li 1 + x Ni y Co z} Mn 1-x-y-z-w lithium transition metal composite oxide represented by M w _{O 2} is first prepared a transition metal complex compound. At that time, the chemical composition _{formula: Ni y Co z Mn 1-} y-z-w M w (OH) a transition metal complex hydroxide represented by ₂ is particularly preferred. As is apparent from the above general formula, Li is contained in a slightly excessive amount with respect to a transition metal of a typical lithium transition metal composite oxide (chemical formula: Li _{1 + x} Ni _y Co _z Mn _1-x-y-z O ₂ ). Things are also included.

  Although the lithium salt to be used is not particularly specified, lithium carbonate and lithium hydroxide are preferable. When y <0.6, lithium carbonate is suitable, and when y is 0.6 or more, lithium hydroxide is suitable. The average particle diameter of the lithium salt is preferably 10 μm or less in consideration of the reactivity with the transition metal composite compound.

  Zirconium oxide is added and mixed in an amount of 0.1 to 1.0% by mass with respect to the lithium transition metal composite oxide. When the addition amount is less than 0.1% by mass, the effect of suppressing the increase in resistance and the effect of suppressing the decrease in discharge capacity and discharge voltage due to charge / discharge cycles when the secondary battery is placed in a high-temperature environment are not seen. On the other hand, when it is larger than 1.0% by mass, there arises a problem that the initial capacity / charge / discharge efficiency is reduced.

  The firing step is performed subsequent to the mixing step. The firing step includes a first firing step in which the firing temperature is maintained at 500 ° C. or higher and 700 ° C. or lower, and a continuous firing step without lowering the firing temperature from the first firing step. After the firing temperature is temporarily reduced to room temperature from the second firing step or the first firing step in which the firing temperature is maintained at 700 ° C or higher and 1000 ° C or lower, the firing temperature is maintained at 700 ° C or higher and 1000 ° C or lower. A second firing step is performed.

  In the first firing step, firing is performed at 500 to 700 ° C. for 2 to 10 hours. The reason for setting the temperature to 500 to 700 ° C. is that the reaction between the Li salt and the transition metal composite compound occurs in this temperature range.

  In the second firing step, firing is performed at 700 to 1000 ° C., which is higher than that in the first firing step, for 5 to 30 hours to promote the reaction. If the temperature is higher than 1000 ° C., the growth of primary particles and the sintering of the particles progress, which is not preferable. If the temperature is lower than 700 ° C., the primary particles do not grow sufficiently, and the crystallinity becomes low. In addition, the desired composition cannot be obtained, which is not preferable.

  A suitable baking time is not generally determined by a combination with the temperature, but is preferably 2 to 10 hours in the first baking step and 5 to 30 hours in the second baking step.

  The lithium transition metal composite oxide synthesized (calcined) is adjusted to a maximum particle size of 50 μm or less. If the maximum particle size exceeds 50 μm, the dispersion of the particles becomes large, and heat is easily generated during charge / discharge, which causes a problem of deterioration. The particle size adjusting means may be, for example, a roll mill, a jet mill, a sieve, or the like without any particular limitation.

When the lithium transition metal composite oxide according to the present invention is used as a positive electrode active material, as in the case of a normal lithium transition metal composite oxide, the negative electrode active material can store and release lithium such as a carbon material and a lithium storage alloy. A nonaqueous electrolytic solution in which a lithium salt is dissolved in a resin or a resin is used as the electrolytic solution. For example, lithium hexafluorophosphate (LiPF6) is used as a lithium salt, and a mixed solution of ethylene carbonate and diethyl carbonate is used as a non-aqueous electrolyte. In addition, as the lithium salt, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSO ₃ CF ₃ , LiN (SO ₃ CF ₃ ) ₂ , and a mixture thereof are used. In addition, as the non-aqueous electrolyte, it is possible to use diethyl carbonate, propylene carbonate, vinylene carbonate and the like, a mixture thereof, and a polymer solid electrolyte (resin) having a high ionic conductivity having polyethyleneimine or the like as a main chain. is there.

  Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. The present invention is not limited to the embodiments.

(Example 1)
Formula _{Li 1.02 Ni 0.49 Co 0.20 Mn 0.29} O 2 and comprising as adjusted lithium carbonate, a transition metal complex compound _{(Formula: Ni 0.5 Co 0.2 Mn 0.3 (} OH) 2 ), Zirconium oxide having a specific surface area of 60 m ² / g was added to the lithium transition metal composite oxide in a ratio of 0.5% by mass, and dry-mixed with a precision mixer, and then at 650 ° C. for 3 hours. Subsequently, the mixture was calcined at 870 ° C. for 8 hours to synthesize a lithium transition metal composite oxide to which zirconium oxide was attached. The obtained lithium transition metal composite oxide was pulverized so that the maximum particle diameter became 50 μm or less, to prepare an active material of Example 1.

(Battery fabrication)
Using the obtained active material of Example 1, acetylene black as a conductive material and KF polymer # 1120 manufactured by Kureha Corporation as a binder were used, and the ratio of active material: conductive material: binder was 90: 6: 4. (Mass ratio) to prepare a positive electrode slurry. The slurry was applied to a collector made of aluminum by a doctor blade method, dried, and then punched into a disk having a diameter of 11 mm and a thickness of 0.3 mm to produce a positive electrode. It was molded under pressure at a pressure of 20 MPa, and dried under reduced pressure at 120 ° C. for 8 hours to obtain a positive electrode plate. For the negative electrode, 0.21 mm-thick metal lithium cut out to about 15 mm square is used. For the electrolytic solution, 1 mol of solute LiPF6 is dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 3: 7. Using a porous polypropylene membrane for the separator, a CR2032 type with a diameter of 20 mm and a height of 3.2 mm (using a component cap, case, gasket, spacer, and wave washer manufactured by Hosen Co., Ltd.) A coin-type lithium secondary battery was manufactured.

  First, the initial charge capacity and initial charge / discharge efficiency of the manufactured coin-type lithium secondary battery were measured in a constant temperature bath at 25 ° C. The charging was terminated when the current reached 2 mA / g at a constant rate of 35 mA / g and an upper limit of 4.25 V constant current and constant voltage. The discharge was performed at a rate of 35 mA / g and a discharge lower limit voltage of 3.0 V. The initial charge / discharge efficiency was calculated as a ratio (%) obtained by dividing the initial discharge capacity by the initial charge capacity.

  Next, the coin-type lithium secondary battery after the initial capacity measurement was repeatedly charged and discharged in a 45 ° C. constant temperature bath at a charging and discharging current of 80 mA / g in a potential range of 3.0 V to 4.3 V 120 times. The test was performed. The initial charge capacity / initial charge / discharge efficiency and the maximum discharge capacity in 120 cycles were set as the first cycle, and the results of the discharge capacity maintenance rate after 100 cycles are shown in Table 1. FIG. 3 shows the results of comparing the average discharge voltage for each cycle with the discharge voltage maintenance ratio.

  After the cycle evaluation described above, the coin-type lithium secondary battery was charged to a SOC of 100% in a constant temperature bath at 25 ° C., and the impedance was measured. VSP manufactured by Bio-Logic was used as a measuring device. The measurement conditions were an amplitude of ± 10 mV and a frequency of 200 kHz to 10 mHz. The measurement results were plotted on a complex plane to create a Cole-Cole plot. The result is shown in FIG.

(Example 2)
Example 2 An active material was prepared in the same manner as in Example 1, except that zirconium oxide having a specific surface area of 90 m ² / g was used.

  A coin-type lithium secondary battery was manufactured, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured in the same manner as in Example 1. The results are shown in Table 1 and FIG. FIG. 3 also shows the results of comparison of the average discharge voltage for each cycle with the discharge voltage maintenance ratio.

(Example 3)
Example 3 An active material of Example 3 was produced in the same manner as in Example 1, except that zirconium oxide having a specific surface area of 30 m ² / g was used. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG. FIG. 3 also shows the results of comparison of the average discharge voltage for each cycle with the discharge voltage maintenance ratio.

(Example 4)
Example 4 An active material was produced in the same manner as in Example 1 except that the chemical formula: Ni _0.5 Co _0.2 Mn _0.25 Al _0.05 (OH) ₂ was used as the transition metal composite compound. . Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Example 5)
Example 5 An active material was prepared in the same manner as in Example 1, except that the chemical formula: Ni _0.5 Co _0.2 Mn _0.27 Mg _0.03 (OH) ₂ was used as the transition metal composite compound. . Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Example 6)
Example 6 An active material was produced in the same manner as in Example 1, except that the chemical formula: Ni _0.5 Co _0.2 Mn _0.29 W _0.01 (OH) ₂ was used as the transition metal composite compound. . Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Example 7)
Example 7 An active material was prepared in the same manner as in Example 1, except that the chemical formula: Ni _0.5 Co _0.2 Mn _0.29 Zr _0.01 (OH) ₂ was used as the transition metal composite compound. . Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Example 8)
Lithium carbonate and a transition metal composite compound (chemical formula: Ni _1/3 Co _1/3 Mn _1/3 (OH) ₂ ) so that the chemical formula is Li _1.01 Ni _0.33 Co _0.33 Mn _0.33 O _2. Then, zirconium oxide having a specific surface area of 60 m ² / g was added to the lithium transition metal composite oxide at a ratio of 0.5% by mass, and dry mixing was performed with a precision mixer. Thereafter, the mixture was calcined at 650 ° C. for 3 hours and subsequently at 950 ° C. for 15 hours to synthesize a lithium transition metal composite oxide to which zirconium oxide was attached. The obtained lithium transition metal composite oxide was pulverized so that the maximum particle diameter became 50 μm or less, to produce an active material of Example 8.

  Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Example 9)
Lithium hydroxide monohydrate, a transition metal composite compound (chemical formula: Ni _0.8 Co _0.1 Mn _0.1 so that the chemical formula is Li _1.01 Ni _0.79 Co _0.1 Mn _0.1 O ₂ (OH) ₂ ), zirconium oxide having a specific surface area of 60 m ² / g was added at a ratio of 0.5% by mass with respect to the lithium transition metal composite oxide, and dry-mixed with a precision mixer, followed by oxygen flow. At 600 ° C. for 5 hours and subsequently at 780 ° C. for 20 hours to synthesize a lithium transition metal composite oxide to which zirconium oxide was attached. The obtained lithium transition metal composite oxide was pulverized so that the maximum particle diameter became 50 μm or less, to produce an active material of Example 9.

  Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Comparative Example 1)
Comparative Example 1 An active material was produced in the same manner as in Example 1, except that zirconium oxide was not added. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG. FIG. 3 also shows the results of comparison of the average discharge voltage for each cycle with the discharge voltage maintenance ratio.

(Comparative Example 2)
Comparative Example 2 An active material was produced in the same manner as in Example 1, except that zirconium oxide having a specific surface area of 12 m ² / g was used. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

Comparative Example 3 An active material was produced in the same manner as in Example 1, except that zirconium oxide having a specific surface area of 120 m ² / g was used. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Comparative Example 4)
Comparative Example 3 An active material was produced in the same manner as in Example 1, except that the addition amount of zirconium oxide was 0.05% by mass. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Comparative Example 5)
Comparative Example 5 An active material was produced in the same manner as in Example 1, except that the amount of zirconium oxide added was changed to 1.5% by mass. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Comparative Example 6)
Comparative Example 6 An active material was produced in the same manner as in Example 8, except that zirconium oxide was not added. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

(Comparative Example 7)
Comparative Example 7 An active material was produced in the same manner as in Example 9 except that zirconium oxide was not added. Similarly, a coin-type lithium secondary battery was prepared, and the initial charge capacity / initial charge / discharge efficiency, discharge capacity maintenance ratio, and impedance were measured. The results are shown in Table 1 and FIG.

From Table 1 and FIGS. 1, 2 and 3, according to the present invention, the lithium transition metal composite oxide is limited to have a maximum particle diameter of 50 μm or less, and further has an oxidation specific surface area of 30 to 90 m ² / g. By attaching zirconium to the surface of the lithium transition metal composite oxide,
(1) The discharge capacity retention rate after 100 cycles of charge and discharge shown in Table 1 is improved,
(2) Out of the two semicircles of the Cole-Cole plots shown in FIGS. 1 and 2, the right semicircle indicating the magnitude of the diffusion transfer resistance is smaller than the comparative example, so the effect of the present invention is confirmed. I can do it.
(3) Further, the average discharge voltage of the example shown in FIG. 3 was higher than that of the comparative example, and it was confirmed that the decrease of the discharge voltage was suppressed.

Claims (4)

The chemical composition is represented by a general formula Li _{1 + x} Ni _y Co _z Mn _1-x-y-z-w M _w O ₂ , wherein M is one or two selected from Al, Mg, W and Zr. X is -0.05≤x≤0.05, y is 0.3≤y <0.9, z is 0.05≤z≤0.35, w is 0≤w≤ 0.1 to 1.0% by mass of zirconium oxide having a specific surface area of 30 to 90 m ² / g adheres to the surface of the lithium transition metal composite oxide particles on the lithium transition metal composite oxide having a range of 0.1. A lithium transition metal composite oxide comprising a composite particle having a maximum particle diameter of 50 μm or less. First calcination in which zirconium oxide having a specific surface area of 30 to 90 m ² / g is mixed with a lithium salt and a transition metal composite hydroxide in a dry manner at the same time or in order, and then the calcination temperature is maintained at 500 ° C. or more and 700 ° C. or less. Step and the second firing step, which is performed continuously without lowering the firing temperature from the first firing step, and the firing temperature is maintained at 700 ° C. or higher and 1000 ° C. or lower. after lowering to room temperature, a manufacturing method of claim 1 lithium transition metal composite oxide according to the firing temperature and firing the second firing step is maintained below 1000 ° C. 700 ° C. or higher. Claim 2 The amount of the zirconium oxide of the lithium salt and a transition metal complex hydroxide and simultaneously or mixed in sequence is characterized in that 0.1 to 1.0 wt% of the lithium-transition metal composite oxide 3. The method for producing a lithium transition metal composite oxide according to item 1. So that the general formula _{Li 1 + x Ni y Co z} Mn 1-x-y-z-w lithium transition metal composite oxide represented by M w _{O 2,} a mixture of lithium salt and a transition metal complex compound, wherein Simultaneously or sequentially, mixing zirconium oxide particles having a specific surface area of 30 to 90 m ² / g, and firing the mixed powder to form composite particles having zirconium oxide adhered to the surface of the lithium transition metal composite oxide. The method for producing a lithium transition metal composite oxide according to claim 2 or 3, wherein:

Images