KR20080022057A - Lithium manganate for positive electrode sub-active material of lithium secondary battery, method for preparing lithium manganate, positive electrode active material of lithium secondary battery and lithium secondary battery - Google Patents

Abstract

A lithium manganate for a positive electrode sub-active material of a lithium secondary battery is provided to suppress a deterioration of performances caused by overdischarge while minimizing reduction in discharge capacity under normal conditions. A lithium manganate for a positive electrode sub-active material of a lithium secondary battery is represented by the formula of Li_xMnO_2(wherein, x is in the range of 0.90<=x<=1.05) and has an L* value of 25.0 to 32.0, an a* value of -1.50 to -0.15, and a b* value of 2.50 to 8.00 in an L*a*b* color matrix system. The lithium manganate has an average particle size of 1-25 micron and a BET specific surface area of 0.2-2.0 m^2/g. When the lithium manganate is dispersed in water, pH of the dispersion is 12 or less.

Description

Lithium Manganate for Positive Electrode Sub-Active Material of Lithium Secondary Battery, Method for Preparing Lithium Manganate, Positive Electrode Active Material of Lithium Secondary Battery and Lithium Secondary Battery}

The present invention relates to a lithium manganate used as a positive electrode activating material of a lithium secondary battery and a method for producing lithium manganate, a lithium secondary battery positive electrode active material containing lithium manganate as a positive electrode activating material, and a lithium secondary battery It is about.

BACKGROUND ART In recent years, as portable and wireless home appliances have been rapidly developed, lithium ion secondary batteries have been put into practical use as power sources for small electronic devices such as laptop personal computers, mobile phones, and video cameras. For such a lithium ion secondary battery, reports of lithium cobalate as a positive electrode active material of a lithium ion secondary battery by Mizushima et al. In 1980 ("Material Research Blutin" vol 15, P783 to 789 (1980)) have been proposed. Since then, research and development on lithium-based composite oxide has been actively progressed, and many proposals have been made so far.

However, a lithium secondary battery using a lithium-based composite oxide as a positive electrode active material is likely to deteriorate in charge and discharge characteristics as a result of the copper foil used as the negative electrode current collector eluting in the electrolytic solution during overdischarge and part of the precipitate in the positive electrode. Had a problem. For this reason, a method of preventing an overdischarge itself by providing an electric circuit to prevent overdischarge is used. However, an electric circuit that prevents overdischarge is present. The cost is high.

The positive electrode active material of the lithium secondary battery is a positive electrode active material containing a lithium-based composite oxide as a main active material and not containing an activating material. On the other hand, a lithium-based composite oxide such as LiCoO _{2 is used} as the main active material, and LiMnO ₂ is added to and used as the activating material, that is, a lithium-based composite oxide such as LiCoO ₂ as the main active material and the activating material. Lithium secondary battery positive electrode active material containing LiMnO ₂ as the above has been proposed. For example, Japanese Patent Laid-Open No. 6-349493 of Patent Document 1 discloses a nonaqueous electrolyte secondary battery produced by mixing LiMnO ₂ with a lithium-containing composite oxide such as LiCoO ₂ as a positive electrode active material. . LiMnO ₂ used in Patent Document 1 is produced by calcining MnO ₂ and lithium carbonate in an inert gas atmosphere. However, in a lithium secondary battery using LiMnO ₂ obtained in Patent Document 1 as a positive electrode activating material, there is a problem of overdischarge. Although it improved to some extent, it was easy to produce problems, such as a fall of discharge capacity in normal use. Therefore, the development of the lithium secondary battery positive electrode activating material which can give the lithium secondary battery the outstanding battery performance was calculated | required.

In addition, Japanese Patent Laid-Open No. 2002-151079 of Patent Document 2 discloses a lithium secondary battery using LiMnO ₂ obtained by firing a mixture of Mn ₂ O ₃ and a lithium compound obtained by heating MnO ₂ as a positive electrode active material. is, but also by using LiMnO ₂ of the Patent Document 2 as a positive electrode resurrection material, it is insufficient as a solution of the problems such as reduction in the over-discharge, and the discharge capacity before the problem.

In addition, the present applicant proposes lithium manganate used for lithium secondary battery positive electrode activating material in Japanese Patent Laid-Open No. 2005-235416 in Patent Document 3 or Japanese Patent Laid-Open No. 2006-139945 in Patent Document 4. . According to the lithium secondary battery positive electrode activator of patent document 3 or patent document 4, although problems, such as a problem of overdischarge and a fall of discharge capacity, can be improved to some extent, further improvement is calculated | required.

[Patent Document 1] Japanese Unexamined Patent Application Publication No. Hei 6-349493 (Patent Claims)

[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-151079 (claims, Example 2)

[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2005-235416 (claims)

[Patent Document 4] Japanese Patent Application Laid-Open No. 2006-139945 (claims)

Therefore, the subject of this invention is a lithium secondary battery positive electrode activating material which is hard to fall in discharge capacity in normal use, and has little deterioration of the performance by over discharge, the manufacturing method, lithium using the said lithium secondary battery positive electrode activating material. A secondary battery positive electrode active material, and a lithium secondary battery which hardly degrades a discharge capacity in normal use, and little in performance deterioration by overdischarge.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to solve the subject in the said prior art, the lithium manganate which has a specific range of color in a L ^* a ^* b ^* color system is excellent as a positive electrode activator, Specifically, the present inventors have found that battery performance that the capacity is less likely to be lowered in normal use and that the superior overdischarge suppressing effect is excellent can be imparted to the lithium secondary battery, thereby completing the present invention.

That is, the present invention (1) is represented by the following formula (1),

L ^* a ^* b ^* color system is L ^* value of from 25.0 to 32.0, a ^* value of -1.50 to -0.15, b ^* value is to the 2.50 to 8.00

It is to provide a lithium manganate for lithium secondary battery positive electrode active material characterized in that.

Li _x MnO ₂

(Wherein x is 0.90 ≦ x ≦ 1.05).

In addition, the present invention (2) is the first step of firing non-basic manganese carbonate at 500 to 800 ℃ in an inert gas atmosphere of oxygen concentration of 1% by volume or less, to obtain MnO,

A second step of obtaining Mn ₂ O ₃ by firing MnO obtained by performing the first step at 525 to 950 ° C. in an atmosphere having an oxygen concentration of 10% by volume or more, and

Mn ₂ O ₃ and the lithium compound obtained by the second step are mixed so that the molar ratio of lithium atoms to manganese atoms is 0.90 to 1.05 to obtain a reaction raw material mixture, and then the reaction raw material mixture is 1% by volume or less in oxygen. Third step of obtaining lithium manganate by firing at 600 to 950 ° C. in an inert gas atmosphere

It provides a method for producing lithium manganate, characterized in that it comprises a.

In addition, the present invention (3) contains a lithium manganate for lithium secondary battery positive electrode activating material according to the present invention (1) and a lithium composite oxide represented by the following general formula (2): a lithium secondary battery positive electrode activity To provide a substance.

Li _(a) M _(1-b) A _(b) O _(c)

Wherein M represents at least one metal element selected from Co and Ni, and A represents Mg, Al, Ti, Zr, Fe, Cu, Zn, Sn, In, Ca, Ba, Sr and Mn At least one metal element, a being 0.9 ≦ a ≦ 1.1, b is 0 ≦ b ≦ 0.5, and c is 1.8 ≦ c ≦ 2.2.)

The present invention (4) further provides a lithium secondary battery obtained by using the lithium secondary battery positive electrode active material according to the present invention (3) as a positive electrode active material.

According to the present invention, a lithium secondary battery positive electrode activating material, a method for producing the same, and a lithium secondary battery positive electrode activating material thereof, which are capable of suppressing deterioration in performance due to overdischarge while being difficult to reduce discharge capacity in normal use. The lithium secondary battery positive electrode active material used can be provided, and the lithium secondary battery which can hardly reduce the discharge capacity in normal use, and has little deterioration of the performance by overdischarge can be provided.

Lithium manganese of the present invention is represented by the formula (1), L ^* a ^* b ^* lithium in the color system L ^* value of 25.0 to 32.0, a ^* value of -1.50 to -0.15, b ^* value of 2.50 to 8.00 It is lithium manganate for secondary battery positive electrode active material. That is, the lithium manganate of the present invention is lithium manganate used as a lithium secondary battery positive electrode activating material constituting a lithium secondary battery positive electrode active material.

In Formula 1, the value of x is 0.90 ≦ x ≦ 1.05, preferably 0.95 ≦ x ≦ 1.01. When x value exists in the said range, Li supply ability of lithium manganate will increase.

The lithium manganate of the present invention is lithium manganate, which is a single phase in X-ray diffraction analysis.

In addition, the lithium manganate of the present invention is lithium manganate represented by the formula (1), lithium manganate (Lithium manganate represented by the formula (1) has been conventionally used as a lithium secondary battery positive electrode activator Lithium manganate, which has conventionally been used as a lithium secondary battery positive electrode activator, is simply referred to as conventional lithium manganate). That is, the L ^* value in the L ^* a ^* b ^* color system of the lithium manganate of the present invention is 25.0 to 32.0, preferably 26.0 to 31.0, and the a ^* value is -1.50 to -0.15, preferably -1.00 to -0.10, and the b ^* value is 2.50 to 8.00, preferably 3.50 to 7.00. Since the L ^* value, a ^* value, and b ^* value in the L ^* a ^* b ^* color system of the lithium manganate of the present invention are in the above ranges, excellent battery performance can be imparted to the lithium secondary battery, so that the discharge capacity The lithium ion secondary battery which is hard to fall and which has little deterioration of the performance by overdischarge can be obtained. On the other hand, conventional lithium manganate has an L ^* value of about 15 to 40, an a ^* value of about -10 to -5, and a b ^* value of about 11 to 18 in an L ^* a ^* b ^* color system. In addition, in this invention, L ^* value, a ^* value, and b ^* value in a L ^* a ^* b ^* colorimeter are color differences measured with a color difference meter, and are prescribed | regulated to Japanese Industrial Standard JIS Z 8730.

L ^* a ^* b ^* L ^* value in the color space represents brightness, white and the larger the value, being completely blanched at 100, had the smaller the value gum is completely black from O. In addition, the a value and the b value indicate color, and the larger the a value, the deeper the red color, the smaller the a value, the darker the green color, the larger the b value, the darker the yellow color, and the smaller the b value, the blue color is darker.

The lithium manganate of the present invention is a powder, and examples of the color difference measurement of the powder include a method of slurrying a powder sample, a method of pelletizing, a method of filling a dedicated shale, and the like. In lithium, the method of charging and measuring in a saale is preferable. This is undesirable because the composition change due to the separation of Li in the slurry occurs due to the method of slurrying lithium manganate, which causes a color change. This is because a change in color due to reflection, pressurization or the like occurs, which is not preferable.

The average particle diameter of the lithium manganate of the present invention is preferably from 1 to 25 µm, from 4 to 15 µm in that the uniform electrode sheet can be coated and the degradation of battery performance due to concentration of current or the like can be suppressed. Is particularly preferred. In addition, in this invention, an average particle diameter is a value calculated | required by the laser method particle size distribution measuring method.

It is preferable that the BET specific surface area of the lithium manganate of this invention is 0.2-2.0 m <^2> / g in the point which suppresses the performance deterioration of the lithium secondary battery by Mn elution, or can supply Li at high speed. , 0.4 to 1.0 m ² / g is particularly preferred.

The pH of the dispersion liquid when the lithium manganate of the present invention is dispersed in water is preferably 12 or less, particularly preferably 11.5 or less, in that gas generation and gelation of the positive electrode mixture paint are suppressed. The lower limit of the pH of the dispersion when the lithium manganate of the present invention is dispersed in water is preferably pH 9.5 because the lithium manganate itself of the present invention is weakly basic. In the present invention, the pH when the lithium manganate was dispersed in water is 100 g of pure water to 5 g of the lithium manganate sample, stirred at 25 ° C. for 5 minutes, and then left to stand for 5 minutes. The value of pH measured by the pH meter is shown.

The lithium manganate of the present invention is contained in a lithium secondary battery positive electrode active material, that is, in combination with a lithium secondary battery main active material as a lithium secondary battery positive electrode activator, the battery performance is excellent, that is, discharge in normal use. Provided is a lithium secondary battery that is less likely to deteriorate in capacity and has little deterioration in performance due to overdischarge.

The lithium manganate of the present invention is a Mn ₂ O ₃ Warium compound obtained by firing MnO at 525 ° C. or higher, Mn ₂ O ₃ Although the homogeneous mixture obtained by mixing so that the molar ratio (Li / Mn) of Li atom in a lithium compound with respect to Mn atom in may be 0.90-1.05, it is obtained by baking at 600 degreeC-950 degreeC, Especially the lithium manganate of this invention Lithium manganate obtained by performing the 1st process-the 3rd process according to a manufacturing method in turn is preferable at the point that Li supply ability is large.

The method for producing lithium manganate of the present invention comprises a first step of calcining non-basic manganese carbonate at 500 to 800 ° C. in an inert gas atmosphere having an oxygen concentration of 1% by volume or less; A second step of obtaining Mn ₂ O ₃ by firing MnO obtained by performing the first step at 525 to 950 ° C. in an atmosphere having an oxygen concentration of 10% by volume or more; And mixing the Mn ₂ O ₃ and the lithium compound obtained by the second step so that the molar ratio (Li / Mn) of the lithium atom to the manganese atom is 0.90 to 1.05 to obtain a reaction raw material mixture, and then the reaction raw material mixture is oxygen And a third step of firing at 600 to 950 ° C. in an inert gas atmosphere having a concentration of 1% by volume or less to obtain lithium manganate.

The first step is a step of firing non-basic manganese carbonate to obtain MnO.

The nonbasic manganese carbonate according to the first step refers to manganese carbonate in which the pH of water after adding 10 g of manganese carbonate to 100 g of ultrapure water and stirring at 25 ° C. for 5 minutes is 6.0 to 7.8, preferably 6.5 to 7.6. In addition, the non-basic manganese carbonate according to the first process is different from manganese carbonate generally called basic manganese carbonate. In the case of basic manganese carbonate, the pH of water after adding 10 g of basic manganese carbonate to 100 g of ultrapure waters, and stirring at 25 degreeC for 5 minutes is 8.0 or more.

Non-basic manganese carbonate is industrially produced by ammonium carbamate solution with aqueous ammonia and carbon dioxide gas, and reacted with manganese monoxide or divalent manganese salts such as manganese sulfate and manganese chloride dissolved in water. It is manufactured by a method of reacting ammonium bicarbonate as a source of carbonate, and the non-basic manganese carbonate has a low content of manganese hydroxide (Mn (OH) ₂ ). Therefore, the pH of water after adding 10 g of non-basic manganese carbonate to 100 g of ultrapure water and stirring for 5 minutes at 25 degreeC becomes 6.0-7.7, Preferably it is 6.5-7.6.

On the other hand, basic manganese carbonate is manufactured by the method of reacting sodium carbonate as a source of carbonate to divalent manganese salts, such as manganese sulfate and manganese chloride, industrially dissolved in water, and basic manganese carbonate (Mn (OH) )) ₂ ) high in content. Therefore, the pH of water after adding 10 g of basic manganese carbonate to 100 g of ultrapure water and stirring for 5 minutes at 25 degreeC will be 8.0 or more.

The other properties of the non-basic manganese carbonate according to the first step are not particularly limited, but the average of the non-basic manganese carbonate according to the first step is easy to obtain lithium manganate having an average particle diameter of 1 to 25 µm. It is preferable that it is 1-30 micrometers, and it is especially preferable that it is 5-20 micrometers.

In the first step, firing of non-basic manganese carbonate is performed in an inert gas atmosphere having an oxygen concentration of 1% by volume or less, preferably in an inert gas atmosphere having an oxygen concentration of 0 to 0.5% by volume. The compact Mn0 is obtained by baking a non-basic manganese carbonate in the said atmosphere. On the other hand, when oxygen concentration exceeds 1 volume%, dense Mn0 is not obtained. Nitrogen gas, helium gas, argon gas, etc. are mentioned as an inert gas which concerns on a 1st process. In addition, in a 1st process, in order to prevent the oxidation by oxygen at the time of baking non-basic manganese carbonate, a small amount of reducing gases, such as hydrogen, can be included in atmosphere.

The firing temperature of the non-basic manganese carbonate in the first step is 500 to 800 ° C, preferably 550 to 700 ° C. If the calcination temperature of non-basic manganese carbonate is less than 500 degreeC, MnO will not be obtained and if it exceeds 800 degreeC, aggregation will become strong and the filling property of lithium manganate will fall.

Although the baking time of a non-basic manganese carbonate in a 1st process is not specifically limited, Preferably it is 1 to 20 hours, Especially preferably, it is 5 to 15 hours. If the firing time of the non-basic manganese carbonate is less than 1 hour, conversion to MnO is likely to be insufficient, and even if firing for 20 hours or more, a large difference is not seen in the quality of Mn0, which is likely to be inefficient.

Mn0 obtained by performing a 1st process has less impurity content compared with Mn0 obtained by baking other manganese salts, and Mn0 obtained by other baking conditions.

The second step is a step by firing the MnO is obtained by performing the first step is a step for obtaining a Mn ₂ O _3.

At a 2nd process, baking of Mn0 obtained by performing a 1st process is performed in the atmosphere of 10 volume% or more of oxygen concentration, Preferably it is the atmosphere of 15 volume% or more of oxygen concentration, Especially preferably, it is the atmosphere of 20 volume% or more. By carrying out the Mn0 obtained by performing the first step in the atmosphere, a low impurity Mn ₂ O ₃ is obtained. On the other hand, when the oxygen concentration is less than 10%, since oxygen is insufficient, conversion of MnO to Mn ₂ O ₃ is insufficient, and impurities are likely to occur. Usually, it is preferable to perform baking of Mn0 obtained by performing a 1st process in air | atmosphere or oxygen atmosphere.

In a 2nd process, the baking temperature of MnO obtained by performing a 1st process is 525-950 degreeC, Preferably it is 550-750 degreeC. When the calcination temperature of MnO obtained by performing the first step is less than 525 ° C, conversion of MnO to Mn ₂ O ₃ is insufficient, so that the discharge capacity of the lithium secondary battery using lithium manganate as the positive electrode activator is lowered, also exceeds 950 ℃, by the conversion to Mn ₃ O ₄ generated from Mn ₂ O _3, as a result can not be obtained because only lithium manganese oxide is Li supply capacity is low, the performance as the positive electrode material is reduced revived. In addition, when the calcination temperature of MnO obtained by performing the first step exceeds 750 ° C, in a lithium secondary battery using lithium manganate as a positive electrode activator, the voltage at which Li is released (charge voltage) tends to increase. It is preferable that the baking temperature of MnO obtained by performing a 1st process is 550-750 degreeC.

Although the baking time of Mn0 obtained by performing a 1st process in a 2nd process is not restrict | limited in particular, Preferably it is 1 to 20 hours, Especially preferably, it is 5 to 15 hours. If the calcination time of MnO obtained by performing the first step is less than 1 hour, conversion to Mn ₂ O ₃ is likely to be insufficient, and even if calcination for 20 hours or more does not show a large difference in the quality of MnO, it is likely to be inefficient.

The third step is a step for obtaining a lithium manganese oxide by calcining a reaction raw material mixture obtained by mixing Mn ₂ O ₃ and the lithium compound obtained by performing the second step.

A third step, and mixed with the first second step Mn ₂ O ₃ and the lithium compound obtained subjected to.

As a lithium compound which concerns on a 3rd process, lithium carbonate, lithium hydroxide, lithium nitrate etc. are mentioned, for example, A lithium compound may be either 1 type individually or in combination of 2 or more types. The lithium carbonate in the lithium compound according to the third step does not have deliquescent properties, does not generate water as a reaction byproduct, and the pH value of the dispersion liquid when lithium manganate is dispersed in water becomes small. It is preferable at the point. Although the physical properties of the lithium compound according to the third step and the like are not limited, it is preferable that the average particle diameter of the lithium compound according to the third step is 20 µm or less, in that the reaction raw material mixture can be uniformly mixed. It is especially preferable that it is micrometer.

Article obtained by performing the second step Mn ₂ O ₃ and a mixture ratio of the lithium compound according to the third step is subjected to a second step the obtained Mn ₂ O ₃ As the molar ratio (Li / Mn) of Li atoms in the lithium compound according to the third step to Mn atoms in the mixture, 0.90 to 1.05 and the mixing ratio of both of them are 0.95 to 1.01, and lithium manganate having a large Li supply capacity It is preferable at the point which is obtained. On the other hand, when the mixing ratio of Mn ₂ O ₃ obtained by the second step and the lithium compound according to the third step is less than 0.90, unreacted Mn ₂ O ₃ remains to cause Mn elution or lithium of lithium manganate. When the supply capacity becomes small and exceeds 1.05, lithium manganate containing a large amount of Li is formed, so that the pH of the dispersion liquid when dispersed in water becomes high, which causes a decrease in battery safety such as gas generation.

The method of mixing when the mixture of Mn ₂ O ₃ and the lithium compound obtained by performing the second step can be any method of dry or wet, but is dry is preferable in that it is easy to manufacture. In the case of dry mixing, it is preferable to use a blender or the like capable of uniformly mixing the reaction raw material mixture.

In addition, Mn ₂ O ₃ obtained by the second step and a lithium compound are mixed to obtain a reaction raw material mixture.

In the third step, the reaction raw material mixture is then fired, and the firing of the reaction raw material mixture is carried out in an inert gas atmosphere having an oxygen concentration of 1% by volume or less, preferably an inert gas atmosphere having an oxygen concentration of 1000 ppm or less, particularly preferably 100 ppm. It is performed in the following inert gas atmosphere. By calcining the reaction raw material mixture in the above atmosphere, lithium manganate for lithium secondary battery positive electrode activator is obtained, which is unlikely to lower the discharge capacity and deteriorates the performance due to over discharge. On the other hand, when the oxygen concentration exceeds 1% by volume, LiMn ₂ O ₄ , Li ₂ MnO _{3, and the like} are also produced, so that the performance of the lithium manganate obtained as a lithium secondary battery positive electrode activator is low. Nitrogen gas, helium gas, argon gas, etc. are mentioned as an inert gas which concerns on a 3rd process.

The firing temperature of the reaction raw material mixture in the third process is 600 to 950 ° C, preferably 700 to 850 ° C. If the calcination temperature of the reaction raw material mixture is less than 600 ° C, the reaction will be insufficient, and therefore, good lithium manganate will not be obtained, and if it exceeds 950 ° C, lithium manganate having a low Li supply capacity will be obtained.

In the third step, the firing time of the reaction raw material mixture is not particularly limited, but is preferably 1 to 20 hours, particularly preferably 5 to 15 hours. When the firing time of the reaction raw material mixture is less than 1 hour, the reaction is likely to be insufficient, and even when firing for 20 hours or more, a large difference in the quality of lithium manganate is not likely to be inefficient.

In addition, in a 3rd process, baking may be performed repeatedly as needed, and when baking is performed repeatedly, you may bake at lower temperature than the said baking temperature range.

In the third step, after firing, the calcined product is appropriately cooled and pulverized as necessary to obtain lithium manganate. In addition, grinding | pulverization performed as needed is suitably performed when the lithium manganate obtained by baking in a 3rd process is a weakly bound block shape, etc.

The lithium manganate obtained by the third step has an average particle diameter of 1 to 25 µm, preferably 4 to 15 µm, and a BET specific surface area of 0.2 to 2.0 m ² / g, preferably 0.4 to 1.0 m ² / g. . In addition, the lithium manganate obtained by the third step has a L ^* value in the L ^* a ^* b ^* color system of 25.0 to 32.0, preferably 26.0 to 31.0, and a ^* value of -1.50 to -0.15, preferably -1.00 to -0.10, and the b ^* value is 2.50 to 8.00, preferably 3.50 to 7.00.

Further, by variously selecting the production conditions in the method for producing the lithium manganate of the present invention, the L ^* value, a ^* value, and b ^* value in the L ^* a ^* b ^* colorimetric system of the obtained lithium manganate can be selected. have. As such a manufacturing condition,

(i) using non-basic manganese carbonate as a raw material of the first step,

(ii) selecting the oxygen concentration of the atmosphere during firing in the first step,

(iii) selecting the firing temperature during firing in the first step,

(iv) selecting the oxygen concentration of the atmosphere during firing in the second step,

(v) selecting the firing temperature during firing in the second step,

(vi) selecting the type or purity of the lithium compound according to the third step,

(vii) selecting the molar ratio of lithium atoms / manganese atoms in the reaction raw material mixture according to the third step,

(viii) selecting the oxygen concentration of the atmosphere during firing in the third step,

(ix) selecting the firing temperature during firing in the third step

Can be mentioned.

The lithium secondary battery positive electrode active material of the present invention is a lithium secondary battery positive electrode active material containing lithium manganate of the present invention and a lithium composite oxide represented by the following formula (2).

<Formula 2>

Li _(a) M _(1-b) A _(b) O _(c)

Wherein M represents at least one metal element selected from Co and Ni, and A represents Mg, Al, Ti, Zr, Fe, Cu, Zn, Sn, In, Ca, Ba, Sr and Mn At least one metal element, a being 0.9 ≦ a ≦ 1.1, b is 0 ≦ b ≦ 0.5, and c is 1.8 ≦ c ≦ 2.2.)

That is, the lithium secondary battery positive electrode active material of the present invention contains the lithium manganese oxide of the present invention as an activating material, and contains the lithium composite oxide represented by the formula (2) as the main active material.

The lithium manganate of the present invention contained in the lithium secondary battery positive electrode active material of the present invention is as described above, represented by the following formula (1),

<Formula 1>

Li _x MnO ₂

(Wherein 0.90 ≦ x ≦ 1.05, preferably 0.95 ≦ x ≦ 1.01)

The L ^* value in the L ^* a ^* b ^* colorimeter is 25.0 to 32.0, preferably 26.0 to 31.0, the a ^* value is -1.50 to -0.15, preferably -1.00 to -0.10, and the b ^* value is 2.50 Lithium manganate for lithium secondary battery positive electrode activating material, which is from 8.00 to 8.00, preferably 3.50 to 7.00. In addition, the lithium manganate of the present invention contained in the lithium secondary battery positive electrode active material of the present invention preferably has an average particle diameter of 1 to 25 µm, particularly preferably 4 to 15 µm, and more preferably a BET specific surface area. It is 0.2-2.0 m <^2> / g, Especially preferably, it is 0.4-1.0 m <^2> / g, Furthermore, pH of the dispersion liquid when disperse | distributing to water is 12 or less, Especially preferably, it is 11.5 or less.

The lithium composite oxide represented by the above formula (2) is not particularly limited, for _{example, LiCoO 2, LiNiO 2, LiNi} 0 .8 Co 0 .2 O 2, LiNi 0 .8 Co 0 .1 Mn 0 .1 _{O 2, LiNi 0 .4 Co 0} .3 Mn 0 .3 O 2 These lithium composite oxides may be either one kind alone or a combination of two or more kinds. Among these, LiCoO ₂ is widely used industrially and is preferable in that the synergistic effect with lithium manganate for the lithium secondary battery positive electrode active material of the present invention is high.

Physical properties and the like of the lithium composite oxide represented by Chemical Formula 2 are not particularly limited. However, the average particle diameter of the lithium composite oxide represented by Chemical Formula 2 may be 1 to 30 μm in that polarization and poor conductivity can be suppressed. It is preferable and it is especially preferable that it is 3-25 micrometers. In addition, in view of improving battery thermal stability, the BET specific surface area of the lithium composite oxide represented by Chemical Formula 2 is preferably 0.1 to 2.0 m ² / g, and particularly preferably 0.2 to 1.0 m ² / g.

Among the lithium secondary battery positive electrode active materials of the present invention, the content ratio of lithium manganate (inactive material) of the present invention and the lithium composite oxide (main active material) represented by the formula (2) is lithium represented by the formula (2). The lithium manganate of the present invention is preferably 5 to 30 parts by mass, particularly preferably 10 to 20 parts by mass based on 100 parts by mass of the composite oxide. When the content ratio of the lithium composite oxide represented by the formula (2) is in the above range, the discharge capacity of the lithium secondary battery is less likely to decrease, and the deterioration in performance due to overdischarge is reduced. On the other hand, when the lithium manganate of the present invention is less than 5 parts by mass with respect to 100 parts by mass of the lithium composite oxide represented by the formula (2), deterioration in performance due to overdischarge tends to be large, and when it exceeds 30 parts by mass, The discharge capacity tends to be small.

In addition, the lithium manganate of the present invention and the lithium composite oxide represented by Chemical Formula 2 are uniformly mixed to prepare a lithium secondary battery positive electrode active material of the present invention. The mixing method of the lithium manganate of the present invention and the lithium composite oxide represented by Chemical Formula 2 is not particularly limited, and is prepared using a mechanical means in which strong shearing force is applied in a wet method or a dry method. In the wet method, mixing is performed using devices such as a ball mill, a disper mill, a homogenizer, a vibration mill, a sand grinder mill, an attritor, and a strong stirrer. On the other hand, in a dry method, mixing is performed using apparatuses such as a high speed mixer, a super mixer, a turbo sphere mixer, a Henschel mixer, a Nauta mixer, and a ribbon blender. In addition, the mixing method is not limited to the method using the illustrated mechanical means. After mixing, there is no problem even if the particle size is adjusted by grinding with a jet mill or the like according to the purpose.

The lithium secondary battery of the present invention is a lithium secondary battery obtained by using the lithium secondary battery positive electrode active material of the present invention as a positive electrode active material, and includes a nonaqueous electrolyte containing a positive electrode, a negative electrode, a separator, and a lithium salt.

The positive electrode according to the lithium secondary battery of the present invention is formed by applying, for example, drying a positive electrode mixture on a positive electrode current collector.

The positive electrode mixture according to the lithium secondary battery of the present invention includes the lithium secondary battery positive electrode active material of the present invention, a conductive agent, a binder, a filler added as necessary, and the like. That is, in the lithium secondary battery of the present invention, a mixture of the lithium manganate of the present invention and the lithium composite oxide represented by the formula (2) is uniformly coated on the positive electrode as a positive electrode active material. For this reason, in the lithium secondary battery according to the present invention, the load characteristics are hardly lowered and the cycle characteristics are hardly lowered.

The positive electrode current collector according to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not cause chemical change in the battery constituted, for example, stainless steel; nickel; aluminum; titanium; Calcined carbon; Carbon, nickel, titanium, and the thing which surface-treated the surface of aluminum or stainless steel, etc. are mentioned. These materials may be oxidation treatments obtained by oxidizing the surface, or may be surface treatments in which irregularities are applied to the surface of the current collector by surface treatment. Moreover, as a form of a positive electrode electrical power collector, a foil, a film, a sheet, a net, a punched thing, lath body, a porous body, a foam, a fiber group, the molded object of a nonwoven fabric, etc. are mentioned, for example. Although the thickness in particular of the positive electrode electrical power collector which concerns on the lithium secondary battery of this invention is not restrict | limited, It is preferable that it is 1-500 micrometers.

The conductive agent according to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conducting material which does not cause chemical changes in the battery constituted. Examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or electroconductive materials, such as a polyphenylene derivative, are mentioned, As natural graphite, an impression graphite, flaky graphite, earth graphite, etc. are mentioned, for example. These may be either one kind alone or a combination of two or more kinds. In the positive electrode mixture which concerns on the lithium secondary battery of this invention, the content rate of a electrically conductive agent is 1-50 mass%, Preferably it is 2-30 mass%.

As the binder according to the lithium secondary battery of the present invention, for example, starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoro Rhoethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoro Propylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, Polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, Propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoro Ethylene copolymer, ethylene-acrylic acid copolymer or ionic crosslinked thereof (Na ⁺ ions, etc.), ethylene-methacrylic acid copolymer or ionic crosslinked thereof (Na ⁺ ions, etc.), ethylene-methyl acrylate copolymer or ionic crosslinked thereof Sieves (Na ⁺ ions, etc.), ethylene-methyl methacrylate copolymers or ion crosslinked bodies thereof (Na ⁺ ions, etc.), polysaccharides such as polyethylene oxide, thermoplastic resins, polymers having rubber elasticity, and the like, and the like can be given. It may be either one kind alone or a combination of two or more kinds. In addition, when using the compound containing a functional group like reacting with lithium like polysaccharide, it is preferable to add a compound, such as an isocyanate group, and to inactivate the functional group. In the positive electrode mixture which concerns on the lithium secondary battery of this invention, the compounding ratio of a binder is 1-50 mass%, Preferably it is 5-15 mass%.

The filler which concerns on the lithium secondary battery of this invention suppresses volume expansion of a positive electrode, etc., and is added as needed. As a filler, although any fibrous material which does not cause a chemical change in the battery comprised can be used, For example, olefin type polymers, such as a polypropylene and polyethylene; Fibers, such as glass and carbon, are mentioned. Although content of a filler is not specifically limited in the positive electrode mixture which concerns on the lithium secondary battery of this invention, It is preferable that it is 0-30 mass%.

The negative electrode which concerns on the lithium secondary battery of this invention is formed by apply | coating and drying a negative electrode material on a negative electrode collector.

The negative electrode current collector according to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not cause chemical change in the battery configured, and copper, copper alloy, nickel and the like can be given. In particular, copper or a copper alloy is oxidized and dissolved when the positive electrode potential becomes about 3.5 Vvs.Li/Li ^{+ during} overdischarge, but since the lithium secondary battery of the present invention has many lithium ions that contribute to charging and discharging, the positive electrode potential during overdischarge Is lower than 3.5 Vvs.Li/Li ⁺ . Therefore, the safety when copper or a copper alloy is used for the negative electrode for the lithium secondary battery of the present invention is significantly higher than the safety when copper or a copper alloy is used for the negative electrode for a conventional lithium secondary battery. In addition, these materials may be oxidation treatments which oxidized the surface, and may also be surface treatments in which unevenness is applied to the surface of the current collector by surface treatment. Moreover, as a form of the negative electrode electrical power collector which concerns on the lithium secondary battery of this invention, a foil, a film, a sheet, a net, a punched thing, lath body, a porous body, foam, a fiber group, the molded object of a nonwoven fabric, etc. are mentioned, for example. have. The thickness of the negative electrode current collector according to the lithium secondary battery of the present invention is not particularly limited, but is preferably 1 to 500 µm.

The negative electrode material according to the lithium secondary battery of the present invention is not particularly limited, and for example, carbonaceous material, metal composite oxide, lithium metal, lithium alloy, silicon alloy, tin alloy, metal oxide, conductive polymer, chalcogen The compound, Li-Co-Ni system material, etc. are mentioned. As a carbonaceous material which concerns on a negative electrode material, a non-graphitizing carbon material, a graphite type carbon material, etc. are mentioned, for example. As the metal composite oxide according to the negative electrode material, for example, Sn _(p) D ¹ _(1-p) D ² _(q) O _(r) (wherein D ¹ is selected from Mn, Fe, Pb and Ge). Represents one or more elements, D ² represents one or more elements selected from Al, B, P, Si, Group 1, 2, 3, and halogen elements of the periodic table, and p is 0 <p ≦ 1 , q is 1 ≦ q ≦ 3, r is 1 ≦ r ≦ 8); Li _(s) Fe ₂ O ₃ , wherein s is 0 ≦ _s ≦ ₁ ; And compounds such as Li _(t) WO ₂ (wherein t is 0 ≦ t ≦ 1). As the metal oxide according to the negative electrode material, GeO, GeO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi ₂ O _3, may be mentioned the _{Bi 2 O 4, Bi 2 O} 5. Polyacetylene, poly-p-phenylene, etc. are mentioned as a conductive polymer which concerns on a negative electrode material.

The separator according to the lithium secondary battery of the present invention has a large ion permeability and is an insulating thin film having a predetermined mechanical strength. As the separator, a sheet or a nonwoven fabric made of an olefin polymer such as polypropylene, glass fiber or polyethylene, etc. is used from the viewpoint of organic solvent resistance and hydrophobicity. The pore size of the separator according to the lithium secondary battery of the present invention should just be a useful range generally for a battery, for example, 0.01-10 micrometers. The thickness of the separator which concerns on the lithium secondary battery of this invention should just be the range for general batteries, for example, 5-300 micrometers. In addition, when solid electrolytes, such as a polymer, are used as electrolyte mentioned later, a solid electrolyte also serves as a separator.

The nonaqueous electrolyte containing the lithium salt according to the lithium secondary battery of the present invention includes a nonaqueous electrolyte and a lithium salt. As a nonaqueous electrolyte which concerns on the lithium secondary battery of this invention, a nonaqueous electrolyte, an organic solid electrolyte, and an inorganic solid electrolyte are mentioned. Examples of the nonaqueous electrolyte according to the nonaqueous electrolyte include N-methyl-2-pyridinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and γ-buty. Rolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane , Methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, Aprotic organic solvents such as propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propanesultone, methyl propionate and ethyl propionate, and these may be used alone or in combination of two or more thereof. It may be.

As an organic solid electrolyte which concerns on a nonaqueous electrolyte, For example, Polyethylene derivative; Polyethylene oxide derivatives or polymers having polyethylene oxide groups; Polypropylene oxide derivatives or polymers having polypropylene oxide groups; Polymers having an ionic dissociation group such as a phosphate ester polymer, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polyhexafluoropropylene; The mixture of the polymer which has an ionic dissociation group, and the nonaqueous electrolyte solution which concerns on the said nonaqueous electrolyte is mentioned.

Examples of the inorganic solid electrolyte according to the nonaqueous electrolyte include nitrides of nitride, halides, oxyacid salts, and the like, for example, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO. ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , phosphorus sulfide and the like.

Examples of the lithium salt according to the lithium secondary battery of the present invention include lithium salts dissolved in the nonaqueous electrolyte according to the lithium secondary battery of the present invention, and examples thereof include LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , and LiBloCl _10. , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiBloCl ₁₀ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium And lower aliphatic lithium carboxylates, lithium tetraphenyl borate, imides, and the like, and these may be any one type or a combination of two or more types.

The nonaqueous electrolyte according to the lithium secondary battery of the present invention may contain a compound shown below for the purpose of improving discharge, charging characteristics and flame retardancy. Examples of such a compound include pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, and the like. N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, monomer of conductive polymer electrode active material, triethylenephosphonamide, trialkylphosphine And aryl compounds having morpholine, carbonyl groups, hexamethylphosphoric triamide and 4-alkylmorpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonate esters and the like. In particular, in order to make nonaqueous electrolyte electrolyte solution which concerns on the lithium secondary battery of this invention nonflammable, the nonaqueous electrolyte which concerns on the lithium secondary battery of this invention can contain halogen containing solvents, such as carbon tetrachloride and ethylene trifluoride, for example. In addition, in order to impart suitability to the high temperature storage of the lithium secondary battery of the present invention, the nonaqueous electrolyte according to the lithium secondary battery of the present invention may contain carbon dioxide gas.

The lithium secondary battery of the present invention configured as described above has excellent battery performance, particularly in normal use, it is difficult to reduce the discharge capacity, exhibits a continuous voltage change during charge and discharge, and also has a deterioration in performance due to over discharge. It is a battery.

The shape of the lithium secondary battery of this invention may be any shape, such as a button, a sheet, a cylinder, a square, and a coin shape. In addition, the lithium secondary battery of the present invention includes, for example, a notebook computer, a laptop personal computer, a pocket word processor, a mobile phone, a wireless handset, a portable CD player, a radio, a liquid crystal television, a backup power supply, an electric shaver, Electronic devices such as memory cards and video movies, and commercial electronic devices such as automobiles, electric vehicles, and game devices.

<Example>

Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this.

(Example 1)

(Production of lithium manganate)

<Firing of Manganese Carbonate>

Commercially available non-basic manganese carbonate (MnCO ₃ , average particle diameter of 8.1 μm) was calcined at 550 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01% by volume) to obtain a fired product A (MnO). The obtained fired material A was analyzed by XRD analysis to confirm that it was MnO.

In addition, 10 g of the commercially available non-basic manganese carbonate was weighed into a 200 mL beaker, 100 g of ultrapure water was added, and the mixture was stirred at 25 ° C for 5 minutes. Subsequently, the filtrate was filtered and the pH of the filtrate was measured with a pH meter (Horiba Seisakusho Co., F-14). As a result, the pH of the filtrate was 7.14.

<Firing of Mn0>

The fired product A (MnO) obtained as described above was fired at 650 ° C for 10 hours in an air atmosphere (oxygen concentration 21.0 vol%) to obtain a fired product B (Mn ₂ O ₃ ). The obtained fired substance B was analyzed by XRD analysis to confirm that it was Mn ₂ O ₃ .

Firing of the reaction raw material mixture

The fired material B (Mn ₂ O ₃ ) and Li ₂ CO ₃ (average particle diameter 5 μm) obtained as described above were mixed so that the molar ratio (Li / Mn) of Li atoms to Mn atoms became 0.99, thereby reacting raw material mixture. C1 was obtained. Subsequently, the obtained reaction raw material mixture C1 was calcined at 700 ° C for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D1. In addition, it was confirmed that the obtained lithium manganate D1 was LiMnO ₂ in a single phase exhibiting the diffraction peak pattern of ASTM card 23-361.

(The Properties of Lithium Manganate)

<Color difference measurement>

Lithium manganate D1 obtained as described above was charged in a dedicated chale, and the L ^* value, a ^* value, and b ^* value were measured three times using a spectroscopic colorimeter (SE2000, manufactured by Nippon Denki Co., Ltd.). The average value was calculated | required. The results are shown in Table 2.

<Property evaluation>

The average particle diameter and BET specific surface area of lithium manganate D1 obtained as described above were measured. The results are shown in Table 2.

<pH measurement>

To 5 g of lithium manganate D1 obtained as described above, 100 g of pure water was added, followed by stirring at 25 ° C for 5 minutes. Then, after leaving for 5 minutes, the pH of the supernatant was measured by a pH meter (Horiba, Ltd., F-14). The measurement results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

Preparation of Test Cell

85 mass% of lithium manganate D1 obtained by the above, 10 mass% of graphite powder, and 5 mass% of polyvinylidene fluoride were mixed, it was made into a positive electrode mixture, this was disperse | distributed to N-methyl- 2-pyridinone, and the kneading paste was Prepared. The obtained kneading paste was applied to aluminum foil, dried, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate.

Subsequently, the test cell E1 was produced by combining each member, such as a separator, a negative electrode, a collector plate, a mounting bracket, an external terminal, and electrolyte solution, to the obtained positive electrode plate. Among them, lithium metal was used for the negative electrode, copper was used for the current collector, and 1 mol of LiPF ₆ was dissolved in 1 liter of a 1: 1 kneading solution of ethylene carbonate and methyl ethyl carbonate.

<Measurement of initial charge capacity, initial discharge capacity, and average charge voltage of a test cell>

Charge is CCCV mode, cut-off voltage 4.25 V, current density of 2.5 mA / cm ² , cut-off current is 1/20 of 1 C current value, discharge is CCCV mode, cut-off voltage 3.4 V, 2.5 With a current density of mA / cm ² , the cutoff current was 7/200 of the 1 C current, and the initial charge capacity, the initial discharge capacity, and the average charge voltage in the CC region were measured. The results are shown in Table 3.

(Examples 2 to 12)

(Production of lithium manganate)

The fired product B and Li ₂ CO ₃ instead of a mixture of a molar ratio (Li / Mn) of the Li atoms to the Mn atom to be 0.99, the molar ratio of Li atoms to the fired product B and Li ₂ CO ₃ to the Mn atom ( Li / Mn) was mixed so as to have the molar ratio shown in Table 1, and instead of firing the obtained reaction raw material mixture C1 at 700 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%), the obtained reaction raw material mixture (C2 to C12). ) Was carried out in the same manner as in Example 1 except that the firing was carried out at a firing temperature shown in Table 1 in a nitrogen atmosphere (0.01% by volume of oxygen concentration) for 10 hours to obtain lithium manganate D2 to D12. In addition, it was confirmed that all of the obtained lithium manganate D2 to D12 were single-phase LiMnO ₂ exhibiting the diffraction peak pattern of ASTM card 23-361.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D2 to D12 obtained as described above were used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D2 to D12 obtained as described above were used. The results are shown in Table 3.

(Comparative Example 1)

(Production of lithium manganate)

<Firing of Manganese Carbonate>

Baking product A was obtained in the same manner as in Example 1.

<Firing of Mn0>

Baking product B was obtained in the same manner as in Example 1.

Firing of the reaction raw material mixture

The calcined product B obtained as described above and Li ₂ CO ₃ (average particle size 5 μm) were mixed so that the molar ratio (Li / Mn) of Li atoms to Mn atoms became 0.85 to obtain a reaction raw material mixture C13. Subsequently, the obtained reaction raw material mixture C13 was calcined at 750 ° C for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D13. In addition, it was confirmed that the obtained lithium manganate D13 was a mixture of LiMnO ₂ , Mn ₂ O _3, and Mn ₃ O ₄ exhibiting a diffraction peak pattern of ASTM card 23-361.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D13 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D13 obtained as described above was used. The results are shown in Table 3.

(Comparative Example 2)

(Production of lithium manganate)

The fired product B and Li ₂ CO _3, instead of mixing the molar ratio of Li atoms to the Mn atom to be 0.85, and the fired product B and Li ₂ CO _3, the molar ratio of Li atoms to the Mn atom to be 1.10 Lithium manganate D14 was obtained in the same manner as in Comparative Example 1 except that mixing was carried out. In addition, it was confirmed that the obtained lithium manganate D14 was a mixture of LiMnO ₂ , Li ₂ MnO _3, and Li ₄ Mn ₅ O ₁₂ showing the diffraction peak pattern of ASTM card 23-361.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D14 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D14 obtained as described above was used. The results are shown in Table 3.

(Comparative Example 3)

(Production of lithium manganate)

<Firing of Manganese Carbonate>

Baking product A was obtained in the same manner as in Example 1.

<Firing of Mn0>

Baking product B was obtained in the same manner as in Example 1.

Firing of the reaction raw material mixture

The calcined product B obtained as described above and Li ₂ CO ₃ (average particle diameter: 5 µm) were mixed so that the molar ratio of Li atoms to Mn atoms became 1.00 to obtain a reaction raw material mixture C15. Subsequently, the obtained reaction raw material mixture C15 was calcined at 1000 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D15. In addition, it was confirmed that the obtained lithium manganate D15 was a single-phase LiMnO ₂ exhibiting a diffraction peak pattern of ASTM card 72-0411.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D15 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D15 obtained as described above was used. The results are shown in Table 3.

(Comparative Example 4)

(Production of lithium manganate)

Commercially available MnO ₂ (average particle diameter of 3.5 µm) and Li ₂ CO ₃ (average particle diameter of 5 µm) were mixed so that the molar ratio of Li atoms to Mn atoms became 1.00 to obtain a reaction raw material mixture C16. Subsequently, the obtained reaction raw material mixture C16 was calcined at 800 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D16. In addition, it was confirmed that the obtained lithium manganate D16 is a single phase of LiMnO ₂ represents the diffraction peak pattern of ASTM card 72-0411.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D16 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D16 obtained as described above was used. The results are shown in Table 3.

(Comparative Example 5)

Commercially available MnO ₂ (average particle size: 3.5 μm) was calcined at 1000 ° C. for 12 hours in an air atmosphere (oxygen concentration of 21.0% by volume) to obtain a fired product F17 (Mn ₃ O ₄ ). Subsequently, the obtained fired product F17 was fired at 650 ° C for 10 hours in an air atmosphere (oxygen concentration 21.0 vol%) to obtain fired product G17 (Mn ₂ O ₃ ). The resulting fired product G17 and Li ₂ CO ₃ (average particle size 5 μm) were mixed so that the molar ratio of Li atoms to Mn atoms became 1.00 to obtain a reaction raw material mixture C17. Subsequently, the obtained reaction raw material mixture C17 was calcined at 750 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D17. In addition, it was confirmed that the obtained lithium manganate D17 was a single-phase LiMnO ₂ exhibiting a diffraction peak pattern of ASTM card 23-361.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D17 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D17 obtained as described above was used. The results are shown in Table 3.

(Comparative Example 6)

Commercially available MnO ₂ (average particle size 3.5 μm) was calcined at 600 ° C. for 10 hours in an air atmosphere (oxygen concentration 21.0 vol%) to obtain a fired product H18 (Mn ₂ O ₃ ). Subsequently, the resulting fired product H18 and Li ₂ CO ₃ (average particle diameter: 5 mu m) were mixed so that the molar ratio of the Li atom to the Mn atom was 1.00 to obtain a reaction raw material mixture C18. Subsequently, the obtained reaction raw material mixture C18 was calcined at 800 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D18. In addition, it was confirmed that the obtained lithium manganate D18 is a single phase of LiMnO ₂ represents the diffraction peak pattern of the ASTM card 23-361.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D18 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D18 obtained as described above was used. The results are shown in Table 3.

(Comparative Example 7)

Commercially available MnO ₂ (average particle size 3.5 μm) was calcined at 600 ° C. for 5 hours in an air atmosphere (oxygen concentration 21.0 vol%) to obtain a fired product I19 (Mn ₂ O ₃ ). Subsequently, the calcined product I19 and Li ₂ CO ₃ (average particle size 5 μm) were mixed so that the molar ratio of Li atoms to Mn atoms became 1.00 to obtain a reaction raw material mixture C19. Subsequently, the obtained reaction raw material mixture C19 was put into an alumina crucible, and the temperature was raised to 600 ° C. at a temperature rising rate of 200 ° C./h while supplying air into the alumina crucible at a feed rate of 1 L / min, followed by conversion of air to nitrogen gas. It heated up to 800 degreeC at the temperature increase rate of 200 degreeC / h, supplying in an alumina crucible at the feed rate of 1 L / min, and hold | maintained at 800 degreeC for 10 hours as it is. Subsequently, it cooled to room temperature at the temperature-fall rate of 200 degree-C / h, introducing nitrogen gas into the alumina crucible at the feed rate of 1 L / min. The product was then triturated to give lithium manganese D19. In addition, it was confirmed that the obtained lithium manganate D19 was a single-phase LiMnO ₂ exhibiting a diffraction peak pattern of ASTM card 72-0411.

(The Properties of Lithium Manganate)

<Color difference measurement, property evaluation and pH measurement>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D19 obtained as described above was used. The results are shown in Table 2.

(Performance evaluation as a lithium secondary battery positive electrode activator)

<Preparation of test cell and measurement of initial charge capacity, initial discharge capacity and average charge voltage>

Instead of the lithium manganate D1 obtained in Example 1, the same procedure as in Example 1 was carried out except that lithium manganate D19 obtained as described above was used. The results are shown in Table 3.

In addition, in the measurement of the initial discharge capacity, initial charge capacity, and average charge voltage of the test cell, the larger the charge capacity of the test cell and the smaller the discharge capacity, that is, the larger the charge / discharge capacity difference, the more Li is supplied as a positive electrode activating material. Indicates high ability. Typically, for a positive electrode active positive electrode active material constituting the main material, such as LiCoO ₂ is because the discharge capacity of about 160 mAH / g for the charging capacity of 165 mAH / g, the difference is small charging and discharging capacity.

In addition, the lower average charging voltage of the test cell indicates that Li can be supplied from a low voltage, and shows that it is excellent as a Li supply material.

In Examples 1 to 12, it was found that the charge and discharge capacity differences were all very large, 140 mAh / g or more, and the average charging voltage was also low at 3.86 V or less, and the obtained lithium manganate was excellent as a positive electrode activating material. On the other hand, in Comparative Examples 1 and 2, since LiMnO ₂ in single phase was not obtained and the charge / discharge capacity difference was small, it was found that the Li supply capacity was low. Moreover, in Comparative Examples 3-7, since the charge / discharge capacitance difference was small and the average charge voltage was high, it turned out that Li supply ability is low.

Thus, as is apparent from Table 3, the lithium manganate of the present invention had a high initial charge capacity, a large difference in charge and discharge capacity, and a low average charge voltage. In addition, such lithium manganate had a high effect of improving safety during overdischarge.

(Examples 13 to 15 and Comparative Examples 8 to 9)

(Production of Lithium Composite Oxide)

Co ₃ O ₄ were weighed (average particle diameter 5 ㎛) 40.0 g and Li ₂ CO ₃ (average particle diameter 5 ㎛) 8.38 g were thoroughly mixed in a dry, and then fired at 1000 ℃ 5 hours. After firing, the obtained fired product was ground and classified to obtain lithium cobalt hydrate J (LiCo0 ₂ ). The average particle diameter of the obtained lithium cobaltate J was 7.4 m, and the BET specific surface area was 0.38 m ² / g.

(Manufacture of lithium secondary battery)

Lithium manganate shown in Table 4 as the positive electrode activating material and lithium cobaltate J obtained as described above as the positive electrode main active material were mixed in the blending ratio shown in Table 4 to obtain positive electrode active materials K20 to 24. Subsequently, 91 mass% of positive electrode active materials K20-24, 6 mass% of graphite powder, and 3 mass% of polyvinylidene fluoride were mixed, it was made into the positive electrode mixture, this was disperse | distributed to N-methyl- 2-pyridinone, and the kneading paste was prepared. . After apply | coating the obtained kneading paste to aluminum foil, it was dried and crimped | bonded and punched by the disk of diameter 15mm, and the positive electrode plate was obtained. Lithium secondary batteries P20 to 24 were manufactured by combining the obtained positive electrode plates with each member such as a separator, a negative electrode, a current collector plate, a mounting bracket, an external terminal, and an electrolyte solution. Among them, artificial graphite was used for the negative electrode, copper was used for the current collector, and 1 mol of LiPF ₆ was dissolved in 1 liter of a 1: 1 kneading solution of ethylene carbonate and ethyl methyl carbonate.

<Over discharge test>

The lithium secondary batteries P20 to 24 prepared as described above were charged with a constant current up to 4.2 V at a current of 1 CmA at 25 ° C., followed by charging for 3 hours at a constant voltage of 4.2 V, followed by a constant current of 1 CmA. The discharge capacity (hereinafter, referred to as "discharge capacity before overdischarge test") when discharged to 3.0 V was measured. Subsequently, it was left to stand for 2 days at the constant voltage of 0V, and overdischarge was performed. After standing, the battery was charged with a constant current up to 4.2 V at a current of 1 CmA and then charged for 3 hours at a constant voltage of 4.2 V. Discharge capacity). In addition, the following formula (3) calculates the ratio of the discharge capacity after the over-discharge test to the discharge capacity before the over-discharge test to obtain the capacity recovery rate. The results are shown in Table 4. In addition, the battery after the overdischarge test was disassembled, and it was observed whether copper of the negative electrode current collector precipitated on the positive electrode. The results are shown in Table 4.

Capacity recovery rate (%) = (discharge capacity after over discharge test / discharge capacity before over discharge test) × 100

From the results in Table 4, it was found that deterioration in performance due to overdischarge was reduced by using the lithium manganate of the present invention as the positive electrode activator.

(Comparative Example 10)

(Production of lithium manganate)

<Firing of Manganese Carbonate>

Commercial basic manganese carbonate (MnCO ₃ , average particle diameter of 27.0 μm) was calcined at 550 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain a fired product A20 (MnO). The obtained fired product A20 was analyzed by XRD analysis to confirm that it was MnO.

In addition, 10 g of the commercial basic manganese carbonate was weighed into a 200 mL beaker, 100 g of ultrapure water was added, and the mixture was stirred at 25 ° C for 5 minutes. Subsequently, the pH of the filtrate was measured by filtration by measuring with a pH meter. As a result, the pH of the filtrate was 8.11.

<Firing of Mn0>

The fired product A20 (MnO) obtained as described above was fired at 650 ° C for 10 hours in an air atmosphere (oxygen concentration 21.0 vol%) to obtain fired product B20 (Mn ₂ O ₃ ). The obtained fired product B20 was analyzed by XRD analysis to confirm that it was Mn ₂ O ₃ .

Firing of the reaction raw material mixture

The fired product B20 (Mn ₂ O ₃ ) and Li ₂ CO ₃ (average particle diameter 5 μm) obtained as described above were mixed so that the molar ratio (Li / Mn) of Li atoms to Mn atoms became 1.00, thereby reacting raw material mixture. C20 was obtained. Subsequently, the obtained reaction raw material mixture C20 was calcined at 800 ° C. for 10 hours in a nitrogen atmosphere (oxygen concentration of 0.01 vol%) to obtain lithium manganate D20. In addition, it was confirmed that the obtained lithium manganate D20 was a single-phase LiMnO ₂ exhibiting a diffraction peak pattern of ASTM card 72-0411.

(Performance Evaluation of Lithium Manganate as Physical Properties and Lithium Secondary Battery Positive Electrode Resistant Material)

The same procedure as in Example 1 was carried out except that lithium manganate D20 was used instead of lithium manganate D1. The results are shown in Table 2 and Table 3.

Claims (8)

It is represented by the following formula (1), L ^* a ^* b ^* color system is L ^* value of from 25.0 to 32.0, a ^* value of -1.50 to -0.15, b ^* value is to the 2.50 to 8.00 Lithium manganate for lithium secondary battery positive electrode active material, characterized in that. <Formula 1> Li _x MnO ₂ (Wherein x is 0.90 ≦ x ≦ 1.05). The lithium manganate for lithium secondary battery positive electrode activating material according to claim 1, wherein the average particle diameter is 1 to 25 µm. The lithium manganate for lithium secondary battery positive electrode active material according to claim 1 or 2, wherein the BET specific surface area is 0.2 to 2.0 m ² / g. The lithium manganate for lithium secondary battery positive electrode activating material according to any one of claims 1 to 3, wherein the pH of the dispersion liquid when dispersed in water is 12 or less. A first step of calcining non-basic manganese carbonate at 500 to 800 ° C. in an inert gas atmosphere having an oxygen concentration of 1% by volume or less, to obtain MnO, A second step of obtaining Mn ₂ O ₃ by firing MnO obtained by performing the first step at 525 to 950 ° C. in an atmosphere having an oxygen concentration of 10% by volume or more, and Mn ₂ O ₃ and the lithium compound obtained by performing the second step are mixed so that the molar ratio of lithium atoms to manganese atoms is 0.90 to 1.05 to obtain a reaction raw material mixture, and then the reaction raw material mixture has an oxygen concentration of 1% by volume or less. Third step of obtaining lithium manganate by firing at 600 to 950 ° C. in an inert gas atmosphere Method for producing lithium manganate, characterized in that it comprises a. Lithium manganate for lithium secondary battery positive electrode activating materials as described in any one of Claims 1-4, and the lithium composite oxide represented by following formula (2) are contained, The lithium secondary battery positive electrode active material characterized by the above-mentioned. <Formula 2> Li _(a) M _(1-b) A _(b) O _(c) Wherein M represents at least one metal element selected from Co and Ni, and A represents Mg, Al, Ti, Zr, Fe, Cu, Zn, Sn, In, Ca, Ba, Sr and Mn At least one metal element, a being 0.9 ≦ a ≦ 1.1, b is 0 ≦ b ≦ 0.5, and c is 1.8 ≦ c ≦ 2.2.) The lithium secondary battery positive electrode active material according to claim 6, wherein the lithium composite oxide is LiCoO ₂ . A lithium secondary battery obtained by using the lithium secondary battery positive electrode active material according to claim 6 as a positive electrode active material.