JP5539946B2 - Method for producing spinel-type lithium-manganese composite oxide - Google Patents

Description

  The present invention relates to a lithium-manganese composite oxide having a spinel structure, which is useful as a positive electrode active material for lithium ion secondary batteries, and a method for producing the same. The present invention also relates to a lithium ion secondary battery using the lithium / manganese composite oxide as a positive electrode active material.

  As a positive electrode active material constituting a positive electrode of a lithium ion battery, lithium cobaltate, lithium nickelate, lithium manganate, and the like have been developed, including some practical applications.

  Among these, lithium cobaltate has a problem that the raw material cobalt is expensive and the effective storage amount is only about 50% of the theoretical amount. Further, although lithium nickelate has the characteristics that it is inexpensive and has an effective storage capacity that is about 1.4 times that of lithium cobaltate, it has some safety problems. On the other hand, lithium manganate has a slightly lower effective energy storage capacity than lithium cobaltate, but as a positive electrode active material for lithium-ion batteries, the raw material manganese is inexpensive and safety is equivalent to lithium cobaltate. Expected.

  However, in the conventional lithium ion battery using lithium manganate as the positive electrode active material, when charging and discharging are repeated, the discharge capacity gradually decreases, so-called cycle characteristics are inferior to lithium cobaltate. there were. This is thought to be due to the fact that the discharge capacity is gradually reduced due to the dissolution of manganese in the positive electrode active material in the electrolyte solution and the generation of distortion of the lithium manganate crystal due to repeated charge and discharge.

  In order to solve the problems in using lithium manganate as a positive electrode active material, various lithium / manganese composite oxides have been proposed. For example, a lithium-manganese composite oxide in which a part of manganese of lithium manganate is substituted with a metal element such as Al, Ni, Co, Fe, Cr, Ta, V, Ti, Mg, etc. has been proposed (Patent Literature). 1, Patent Document 2, Patent Document 3, and Patent Document 4). In addition, lithium-manganese composite oxides in which part of manganese is substituted with boron have been proposed (see Patent Document 5, Patent Document 6, and Patent Document 7).

  However, the lithium ion battery using the conventional lithium-manganese composite oxide in which a part of these manganese is substituted with different elements does not have inferior high-temperature cycle characteristics or does not necessarily satisfy high-temperature cycle characteristics. It was still insufficient for practical use. Further, these positive electrode active materials are processed into fine particles and blended in a positive electrode mixture, and used for positive electrode formation. By the way, it is possible to improve the battery capacity by filling as much positive electrode active material as possible in a battery of a certain volume, so that as much positive electrode active material as possible can be blended in the positive electrode mixture. Although desirable, the amount of the positive electrode active material that can be blended in the mixture is also limited.

  Therefore, when a fine particulate positive electrode active material having a high packing density is used, the weight of the positive electrode active material filled per unit volume increases, and a battery having a large charge / discharge capacity can be obtained. That is, a positive electrode active material having a large discharge capacity per volume (discharge capacity per weight × packing density) simultaneously with the discharge capacity per weight is preferable. However, conventional lithium manganate fine particles have a smaller packing density than lithium cobaltate having the same particle size, and the positive electrode active material using such lithium manganate has a low discharge capacity per volume, and cobalt acid There was also a problem that there was only about 50 to 60% of lithium.

JP-A-2-220358 Japanese Patent Laid-Open No. 4-141954 JP-A-6-187993 JP-A-9-147867 JP-A-4-237970 JP-A-8-79215 JP-A-8-195200

  The present invention solves the problems of the conventional lithium-manganese composite oxide as described above, and when used as a positive electrode active material of a lithium ion battery, it has excellent high-temperature cycle characteristics and storage stability, An object of the present invention is to provide a novel lithium / manganese composite oxide having a high discharge capacity per volume, a method for producing the same, and a lithium ion secondary battery using such a novel lithium / manganese composite oxide as a positive electrode active material. To do.

The spinel-type lithium / manganese composite oxide according to the present invention is represented by the following general formula.
Li _{(x + y)} Mn _(2-ypq) M1 _p M2 _q O _(4-a) F _a
(Where 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <x + y ≦ 1.2, 0 <p ≦ 1.0, 0.0005 ≦ q ≦ 0.1, 0 ≦ a ≦ 1.0,
M1: at least one metal selected from Ni, Co, Mg, Fe, Al, Cr,
M2: At least one element selected from elements having an oxide melting point of 800 ° C. or lower)
The specific surface area of the spinel type lithium / manganese composite oxide is preferably in the range of 0.1 to 2.0 m ² / g.

The method for producing the spinel type lithium-manganese composite oxide according to the present invention,
(i) a lithium compound, (ii) a manganese compound, (iii) a compound of at least one metal (M1) selected from Ni, Co, Mg, Fe, Al, and Cr, and (iv) a melting point of the oxide of 800 ° C. At least one compound selected from the following elements (M2), and (v) a fluorine compound,
The atomic ratio of Li: Mn: M ₁ : M ₂ : F is (x + y) :( 2-ypq): p: q: a (where 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <X + y ≦ 1.2, 0 <p ≦ 1.0, 0.0005 ≦ q ≦ 0.1, 0 ≦ a ≦ 1.0) to prepare an aqueous suspension,
After drying the aqueous suspension,
It is characterized by firing at a temperature of 650 to 900 ° C.

  The lithium ion secondary battery according to the present invention has a positive electrode containing the spinel type lithium / manganese composite oxide as a positive electrode active material.

  In the lithium-manganese composite oxide according to the present invention, a part of Mn is substituted with a metal element selected from Ni, Co, Mg, Fe, Al, and Cr, and a lithium ion battery using this as a positive electrode active material Has excellent high-temperature characteristics such as storage stability at high temperatures and high-temperature cycle characteristics.

  Furthermore, by adding an element having a melting point of an oxide such as B of 800 ° C. or lower, the crystal is sufficiently grown, and the fine particles that are aggregates of crystal particles are also sufficiently sintered. The specific surface area is small and the packing density of fine particles is also large. Therefore, the lithium ion battery using this as a positive electrode active material has excellent discharge capacity per volume and high temperature characteristics such as storage stability at high temperatures, such as Ni, Co, Mg, Fe, Al, and Cr. And even better than just the replacement.

  In addition, since a part of Mn is replaced with Li, a lithium ion battery using this as a positive electrode active material has improved high-temperature cycle characteristics. Furthermore, when the lithium-manganese composite oxide according to the present invention in which part of oxygen is substituted with fluorine is used as the positive electrode active material, the charge / discharge capacity of the lithium ion battery can be improved.

The spinel-type lithium / manganese composite oxide according to the present invention is represented by the following general formula.
Li _{(x + y)} Mn _(2-ypq) M1 _p M2 _q O _(4-a) F _a
(Where 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <x + y ≦ 1.20 <p ≦ 1.0, 0.0005 ≦ q ≦ 0.1, 0 ≦ a ≦ 1.0,
M1: at least one metal selected from Ni, Co, Mg, Fe, Al, Cr,
M2: At least one element selected from elements having an oxide melting point of 800 ° C. or lower)
Such a lithium-manganese composite oxide has a spinel structure, and a part of the manganese atom in the crystal structure is substituted with the metal M1 and the element M2, and a part of the manganese atom is substituted with the lithium atom. Presumed to have a structure.

  The amount of substitution of the metal M1 is in the range of 0 <p ≦ 1, preferably 0.02 ≦ P ≦ 0.2 in the above general formula. If it exists in such a range, when it uses as a positive electrode active material, fixed discharge capacity can be ensured and a high temperature cycling characteristic can be maintained. Note that when the amount of substitution of the metal M1 is increased, the high-temperature cycle characteristics of the battery when used as the positive electrode active material is improved, but the discharge capacity of the battery may be reduced.

Specific examples of the element M2 having an oxide melting point of 800 ° C. or lower include B (B ₂ O ₃ ; melting point 460 ° C.), P (P ₂ O ₅ ; melting point 420 ° C.), Pb (PbO; melting point 290 ° C.). , Sb (Sb ₂ O ₃ ; melting point 655 ° C.), V (V ₂ O ₅ ; melting point 680 ° C.), and the like. Among these, a particularly preferable element is B or V.
These elements M2 are considered to constitute a structure in which a part of Mn is substituted in the finally obtained lithium / manganese composite oxide.

  The amount of M2 is preferably in the range of 0.0005 ≦ q ≦ 0.1, preferably 0.005 ≦ q ≦ 0.05 in the above general formula. If the element M2 is contained in the lithium-manganese composite oxide within the above range, the resulting lithium-manganese composite oxide has sufficiently grown crystals. If q is less than 0.0005, the effects of crystal growth and fine particle sintering cannot be expected, and if it exceeds 0.1, the discharge capacity of the battery when used as a positive electrode active material may decrease.

  In the present invention, these elements M2 are added to promote the formation and growth of spinel crystals. That is, these elements M2 are fine particles (secondary particles) in which crystal oxides (primary particles) are aggregated by promoting the formation and growth of crystals by the action of oxides of the above elements as fluxes in the process of forming spinel crystals. Promotes sintering of secondary particles). As a result, an extremely dense lithium / manganese composite oxide having a small specific surface area can be obtained.

That is, the spinel type lithium / manganese composite oxide according to the present invention has a crystal particle (primary particle) having a particle size in the range of 0.1 to 5.0 μm, and about 2 to 30 μm in which the primary particles are aggregated and sintered. made from a range of secondary particles of specific surface area thereof, 0.1~2.0m ² / g, preferably from 0.2~0.8m ² / g, packing density, 1.5-2. It is in the range of 5 g / ml.

  The spinel type lithium / manganese composite oxide fine particles as described above have a filling density larger than that of the conventional lithium / manganese composite oxide when filled in a container of a constant volume. Therefore, when used as a positive electrode active material, the weight of the positive electrode active material that can be filled in a battery of a constant volume increases, and the discharge capacity per volume can be increased as compared with the conventional positive electrode active material.

  In addition, since the crystals are sufficiently grown, when this is used as the positive electrode active material, the amount of Mn dissolved in the electrolyte when contacted with the electrolyte is higher than that of the conventional lithium / manganese composite oxide. However, since there are few, the fall of the discharge capacity by repetition of charging / discharging at high temperature is few, ie, the improvement of high temperature cycling characteristics can be aimed at.

If the specific surface area is smaller than 0.1 m ² / g, the Mn dissolution amount decreases, but the contact between the positive electrode active material and the conductive agent and the contact with the electrolytic solution in the positive electrode may be insufficient. On the other hand, if it exceeds 2.0 m ² / g, the packing density decreases, and the discharge capacity per unit volume may not be improved, or the cycle characteristics may not be improved due to an increase in the dissolved amount of Mn.

  In the lithium-manganese composite oxide according to the present invention, part of Mn is further substituted with Li. The theoretical value of Li is 1 in the lithium-manganese composite oxide having a spinel structure used as the positive electrode active material of the lithium ion battery, but in the present invention, an excessive amount of Li is included. By reducing the amount of Mn by an amount corresponding to a part or all of this excess Li, a structure in which at least a part of Li is replaced with Mn is taken. That is, in the above general formula, the total amount of Li (x + y) is desirably in the range of 1.0 <(x + y) ≦ 1.2, preferably 1.05 <(x + y) ≦ 1.15. Further, the Li amount (y) substituting Mn is desirably in the range of 0 <y ≦ 0.2, preferably 0.05 <y ≦ 0.15. When the substitution amount (y) of Li is increased, the charge / discharge capacity of the battery is slightly reduced, but the cycle characteristics are improved. However, even if y is greater than 0.2 (x + y is 1.2), the effect of improving the cycle characteristics is not observed. Moreover, when Li total amount (x + y) becomes 1.0 or less, a heterogeneous phase that is an impurity is generated, and the charge / discharge performance of the battery is lowered.

  In the spinel type lithium / manganese composite oxide according to the present invention, the lithium / manganese composite oxide may further contain fluorine. This fluorine is presumed to have a structure in which a part of oxygen is substituted in the spinel structure. By using the positive electrode active material to which fluorine is added, the charge / discharge capacity of the lithium ion battery can be increased.

  The lithium-manganese composite oxide of the present invention can be produced, for example, by mixing a lithium compound, a manganese compound, and powders of the elements M1 and M2 and then firing the mixture in an oxygen-containing gas atmosphere. Particularly suitable is an aqueous suspension in which a lithium compound, a manganese compound, a compound of elements M1, M2 and a fluorine compound are mixed in a predetermined ratio based on JP-A-10-172567 filed earlier by the present applicant. Is prepared, dried, and then fired at 650 to 900 ° C.

  Hereinafter, the manufacturing method according to the present invention will be specifically described. First, an aqueous suspension (hereinafter referred to as an aqueous suspension A) in which a manganese compound, a substitution element M1 compound and a fluorine compound are dispersed in water or a part thereof is dissolved is prepared. As the manganese compound, manganese oxides such as electrolytic manganese dioxide and chemically synthesized manganese dioxide, or manganese compounds such as manganese hydroxide, manganese carbonate, and manganese nitrate that are thermally decomposed to become manganese dioxide are used. Such a manganese compound is preferably adjusted in advance to an average particle size of 10 μm or less, preferably 0.1 to 5 μm by means of pulverization or the like.

  Examples of the compound of element M1 (one or more metals selected from Ni, Co, Mg, Fe, Al, and Cr) include carbonates such as basic nickel carbonate and basic cobalt carbonate, alumina, magnesia, and the like. Oxides. These compounds also have an average particle diameter of 10 μm or less, preferably 0.1 to 5 μm, similarly to the manganese compound.

  The particle size adjustment may be performed separately for each of the above compounds, or may be performed after mixing all the above compounds. If the average particle size of the solid content in the aqueous suspension is adjusted to such a range, the solid content in the suspension does not undergo solid-liquid separation and is subjected to the next drying step in a uniform state. be able to. As a result, a dry powder in which each compound is mixed extremely uniformly is obtained. If this dried product is fired, solid-state reaction with manganese, lithium, and a substitution element easily proceeds, and a higher-purity composite oxide than a fired product of a mixture of conventional solid powders can be obtained. it can. In the case of adding elemental fluorine, for example, ammonia fluoride, hydrofluoric acid, lithium fluoride, and the like are mixed into the aqueous suspension A described above.

  In the aqueous suspension A prepared as described above, a compound of the element M2 whose melting point of the lithium compound and oxide is 800 ° C. or less is mixed. Examples of the lithium compound include water-soluble lithium compounds such as lithium hydroxide, lithium carbonate, and lithium nitrate. Examples of the M2 compound include acids containing the element M2, water-soluble salts, and the like. Specific examples include water-soluble boron compounds such as boric acid and borax, and water-soluble vanadium compounds such as ammonium metavanadate. .

  The above-mentioned lithium compound and the compound of the element M2 whose melting point of the oxide is 800 ° C. or less may be directly mixed in the prepared aqueous suspension A. You may mix. An aqueous suspension (referred to as water suspension B) containing lithium compounds, manganese compounds, elements M1, M2 and fluorine compounds prepared as described above in a predetermined ratio can be obtained by newly adding water. It is desirable to adjust the solid content concentration to be in the range of 5 to 30% by weight.

  The aqueous suspension B prepared by the above method is then subjected to a drying operation. There is no restriction | limiting in particular as a drying method, For example, the method by a spray dryer, a band dryer, a shelf type dryer etc. is mentioned. In particular, if a spray dryer is used, spherical lithium-manganese composite oxide fine particles can be obtained. As drying conditions at this time, it is preferable that the inlet temperature of the hot air for drying of the spray dryer is in the range of about 290 to 310 ° C and the outlet temperature is about 110 to 120 ° C.

  The fine particles after drying are then fired at a temperature in the range of 650 to 900 ° C. in an oxygen-containing gas atmosphere. This firing operation produces a lithium-manganese composite oxide having a spinel structure and promotes the sintering of fine particles (secondary particles) in which crystal particles are aggregated as crystal growth proceeds. An oxide is obtained.

  Firing is performed in an oxygen-containing gas such as air by an ordinary firing furnace such as a tunnel furnace, a muffle furnace, or a rotary kiln. The specific surface area of the lithium / manganese composite oxide of the present invention decreases as the firing temperature is increased or the amount of the element M2 compound acting as a flux is increased. In the present invention, a lithium-manganese composite oxide having a specific surface area in the range of 0.1 to 2.0 m @ 2 / g can be obtained by appropriately selecting the firing temperature according to the amount of the element M2.

  Furthermore, if the firing is performed at a temperature within the above range, the sintering of the fine particles (secondary particles) in which the crystal particles are aggregated proceeds, and fine fine particles having a larger packing density than the secondary particles obtained by the conventional method can be obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples at all.

[ Reference Example 1]
Electrolytic manganese dioxide powder (γ-MnO ₂ , purity 92%) and cobalt carbonate powder (CoCO ₃ , purity 93%) were charged into a wet grinder at a ratio of Mn: Co = 90: 10 (atomic ratio), and the average particle size It grind | pulverized to the diameter of 0.5 micrometer. Lithium hydroxide aqueous solution and boric acid aqueous solution were added to this mixture slurry so that Li: Co: Mn: B = 1.1: 0.189: 1.701: 0.0095 (atomic ratio) to obtain a solid content concentration. A 20 wt% slurry was prepared.

This slurry was dried with a spray dryer. The conditions of the spray dryer were a hot air inlet temperature of 300 to 310 ° C and an outlet temperature of 110 to 150 ° C. Next, the dried powder is calcined at 850 ° C. for 6 hours under air flow to thereby _produce crystalline lithium manganese having a composition of Li _1.1 Co _0.189 Mn _1.701 B _0.0095 O ₄ (x = 1.0, y = 0.1). Composite oxide fine particles were obtained.

Table 1 shows the average particle diameter, specific surface area and packing density of the fine particles. The measurement method is as follows. Average particle size: Laser diffraction scattering type particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.) Specific surface area: Automatic surface area analyzer (manufactured by Yuasa Ionics Co., Ltd., Multi Soap-12) 25 g was sampled and tapped on a wooden table for 3 minutes, and then its volume (V) was measured.
Packing density (g / ml) = 25 / V

[ Reference Example 2]
Reference Example 1 except that the raw materials were blended so that the atomic ratio of lithium, cobalt, manganese and boron was Li: Co: Mn: B = 1.1: 0.095: 1.796: 0.0095 Crystalline lithium / manganese composite oxide fine particles made of Li _1.1 Co _0.095 Mn _1.796 B ^0.0095 O ₄ (x = 1.0, y = 0.1) were prepared under the same synthesis conditions as described above.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 3]
Reference Example 1 except that the raw materials were blended so that the atomic ratio of lithium, cobalt, manganese, and boron was Li: Co: Mn: B = 1.1: 0.019: 1.872: 0.0095 Crystalline lithium / manganese composite oxide fine particles comprising Li _1.1 Co _0.019 Mn _1.872 B _0.0095 O ₄ (x = 1.0, y = 0.1) were prepared under the same synthesis conditions.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 4]
Reference Example 1 except that the raw materials were blended so that the atomic ratio of lithium, cobalt, manganese and boron was Li: Co: Mn: B = 1.1: 0.092: 1.751: 0.057 Under the same synthesis conditions, fine particles of crystalline lithium / manganese composite oxide composed of Li _1.1 Co _0.092 Mn _1.751 B _0.057 O ₄ (x = 1.0, y = 0.1) were prepared.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Example 5]
Γ-Al ₂ O ₃ (purity: 95%) is used as the aluminum compound, and the atomic ratio of lithium, aluminum, manganese and boron is set to Li: Al: Mn: B = 1.1: 0.095: 1.796: 0. A crystallinity made of Li _1.1 Al _0.095 Mn _1.796 B _0.0095 O ₄ (x = 1.0, y = 0.1) under the same synthesis conditions as in Reference Example 1 except that the raw materials were blended so as to be. Fine particles of lithium-manganese composite oxide were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Example 6]
Magnesium oxide (MgO, purity: 99.8%) is used as the magnesium compound, and the atomic ratio of lithium, magnesium, manganese and boron is Li: Mg: Mn: B = 1.1: 0.047: 1.843. : Li _1.1 Mg _0.047 Mn _1.843 B _0.0095 O ₄ (x = 1.0, y = 0.1) under the same synthesis conditions as in Reference Example 1 except that the raw materials were blended to _0.0095. Crystalline lithium / manganese composite oxide fine particles were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 7]
Nickel hydroxide (Ni (OH) ₂ , purity: 100%) was used as the nickel compound. Reference Example 1 except that the raw materials were blended so that the atomic ratio of lithium, nickel, manganese and boron was Li: Ni: Mn: B = 1.1: 0.095: 1.796: 0.0095 Crystalline lithium-manganese composite oxide fine particles made of Li _1.1 Ni _0.095 Mn _1.796 B _0.0095 O ₄ (x = 1.0, y = 0.1) were obtained under the same synthesis conditions.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 8]
As the chromium compound, chromic anhydride (CrO ₃ , purity: 99.8%) was used, and the atomic ratio of lithium, chromium, manganese and boron was Li: Cr: Mn: B = 1.1: 0.095: 1. 796: From Li _1.1 Cr _0.095 Mn _1.796 B _0.0095 O ₄ (x = 1.0, y = 0.1) under the same synthesis conditions as in Reference Example 1 except that the raw materials were blended so as to be 0.0095. Crystalline lithium / manganese composite oxide fine particles were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 9]
Using iron oxide (Fe ₂ O ₃ , purity: 98%) as the iron compound, the atomic ratio of lithium, iron, manganese and boron is Li: Fe: Mn: B = 1.1: 0.047: 1. 843: From Li _1.1 Fe _0.047 Mn _1.843 B _0.0095 O ₄ (x = 1.0, y = 0.1) under the same synthesis conditions as in Reference Example 1 except that the raw materials were blended so as to be 0.0095. Crystalline lithium / manganese composite oxide fine particles were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 10]
Electrolytic manganese dioxide powder (γ-MnO ₂ , purity 92%) and nickel hydroxide powder (Ni (OH) ₂ , purity 100%) are put into a wet grinder at a ratio of Mn: Ni = 95: 5 (atomic ratio). Charged and ground to an average particle size of 0.5 μm. Lithium hydroxide aqueous solution, boric acid aqueous solution and Li / Ni: Mn: B: F were added to this mixture slurry so as to be 1.1: 0.095: 1.796: 0.0095: 0.095 (atomic ratio). An aqueous ammonium fluoride solution was added to prepare a slurry having a solid concentration of 20% by weight.

This slurry was dried with a spray dryer under the same conditions as in Reference Example 1. Next, the dry powder is calcined at 850 ° C. for 6 hours under air flow to thereby _obtain crystalline lithium manganese composed of Li _1.1 Ni _0.095 Mn _1.796 B _0.0095 O _3.905 F _0.095 (x = 1.0, y = 0.1). Composite oxide fine particles were obtained. Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[ Reference Example 11]
Except that the atomic ratio of lithium, nickel, manganese, boron and fluorine is Li: Ni: Mn: B: F = 1.1: 0.095: 1.796: 0.0095: 0.19 Crystalline lithium / manganese composite oxide particles comprising Li _1.1 Ni _0.095 Mn _1.796 B _0.0095 O _3.81 F _0.19 (x = 1.0, y = 0.1) were obtained under the same synthesis conditions as in Reference Example 10. It was.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Comparative Example 1]
Li _1.1 Co _0.095 Mn _1.805 O ₄ (x = 1.0, y = 0) under the same synthesis conditions as in Reference Example 1 except that boron was not added and the amounts of lithium and cobalt were the same as in Reference Example 2. (1) Crystalline lithium / manganese composite oxide fine particles were obtained. Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Comparative Example 2]
Except for the atomic ratio of lithium, manganese and boron being Li: Mn: B = 1.1: 1.89: 0.0095, the same synthesis conditions as in Reference Example 1 were used except for Li and B. Crystalline lithium / manganese composite oxide fine particles made of Li _1.1 Mn _1.89 B _0.0095 O ₄ (x = 1.0, y = 0.1) having no substitution element were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Comparative Example 3]
Li _1.0 Co _0.10 Mn _1.89 B _0.0095 O ₄ (x = 1.0, under the same synthesis conditions as in Reference Example 1 except that Li is the theoretical amount and the substitution amounts of Co and B are the same as in Reference Example 2. Crystalline lithium / manganese composite oxide fine particles comprising y = 0) were obtained. Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Comparative Example 4]
The powders of electrolytic manganese dioxide, cobalt carbonate, lithium hydroxide and boric acid used in Reference Example 1 were respectively replaced with Li: Co: Mn: B = 1.1: 0.095: 1.796: 0.0095 (atomic ratio). Then, the mixture was collected in a mortar, ground, and mixed. Next, this mixture was calcined at 850 ° C. for 6 hours under air flow, and a crystalline lithium / manganese composite oxide composed of Li _1.1 Co _0.095 Mn _1.796 B _0.0095 O ₄ (x = 1.0, y = 0.1). Fine particles were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.

[Example 12]
Test lithium ion batteries were prepared using positive electrodes containing the crystalline lithium / manganese composite oxides obtained in Examples 5 to 6 and Reference Examples 1 to 4 and 7 to 11 as a positive electrode active material, and battery performance was evaluated. did.
First, fine particles of each crystalline lithium / manganese composite oxide, acetylene black as a conductive material, and polytetrafluoroethylene powder as a binder are mixed at a weight ratio of 75: 20: 5 and kneaded in a mortar. A positive electrode mixture was prepared. This mixture was made into a sheet having a thickness of 0.1 mm with a stretch roller, die-cut to 16 mmφ, and vacuum dried at 110 ° C. to prepare a test positive electrode.

These positive electrode and metallic lithium foil (thickness 0.2 μm) are laminated on a coin-type battery case via a separator (trade name: Celgard), and 1 mol / l in a 1: 1 volume ratio of ethylene carbonate and dimethyl carbonate mixed solvent. An electrolyte solution in which 1 LiPF ₆ was dissolved was injected to prepare a test battery.

The above battery was subjected to discharge capacity, high temperature cycle characteristics, and high temperature deterioration test.
(1) First, after measuring the discharge capacity per weight under the conditions of a current regulation of 0.5 mA / cm ² at a constant discharge capacity, potential regulation up to a charging potential of 4.3 V and a discharging potential of 3.0 V, The discharge capacity per volume was calculated from the equation.
Discharge capacity per volume = discharge capacity per weight x packing density

(2) The battery for high temperature cycle characteristic test was installed in a 60 degreeC thermostat, the charge / discharge test was performed 30 times on the same conditions as the above, and the high temperature cycle characteristic was evaluated by the capacity maintenance rate of following Formula.
Capacity maintenance rate (%) =
(Discharge capacity per first weight / discharge capacity per 30th weight) × 100

(3) High temperature degradation test (Evaluation of high temperature storage stability)
The performance degradation of the positive electrode active material after being immersed in a high temperature electrolyte for a certain time was evaluated using the recovery rate of the discharge capacity as an index.

First, the positive electrode active material sample was dried at 110 ° C. for 3 hours, and about 10 g thereof was collected in a stainless steel container with a lid having a volume of 50 ml. This was transferred into an argon gas circulation glove box having a dew point of about −70 ° C., and 10 ml of an organic solvent in which 1 mol / l LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate having a volume ratio of 1: 1 was added. After sealing the container, it was taken out from the glove box, transferred to a constant temperature bath set at 85 ° C., and held for 7 days. Next, the container was taken out and cooled to room temperature, and then the sample in the container and the organic solvent were separated by filtration and dried at 110 ° C. for 3 hours.

Using the positive electrode active material thus treated, the same test positive electrode and test battery as described above were prepared.
The charge / discharge test of these test electrodes was performed under the conditions described above, and the recovery rate was calculated by the following formula.
A: Discharge capacity of battery using treated positive electrode active material B: Discharge capacity recovery rate of battery using untreated positive electrode active material (%) = (A / B) × 100
(The discharge capacity is the value in the second cycle) Table 2 shows the results of the discharge capacity, high-temperature cycle characteristics and recovery rate obtained above.

[Comparative Example 5]
Using the positive electrode containing the crystalline lithium / manganese composite oxide obtained in Comparative Examples 1 to 4 as a positive electrode active material, a test lithium ion battery was prepared in the same manner as in Example 12, and the battery performance was evaluated.
The results are shown in Table 2.

The following can be understood from the above Examples , Reference Examples, and Comparative Examples.
(1) Comparing Reference Example 2 and Comparative Example 1 having the same composition except for the presence or absence of boron addition, Reference Example 2 has a smaller specific surface area and a larger packing density. Therefore, both the capacity retention rate and the recovery rate are superior to those of Comparative Example 1.
(2) Compared to Reference Example 1 and Comparative Example 2 having the same composition except for the presence or absence of the substitution metal M1, Reference Example 1 is superior in both capacity retention rate and recovery rate.
(3) When the lithium is the theoretical amount (1.0) as in Comparative Example 3, the capacity retention rate is inferior to each of the Examples in which lithium is 1.0 or more and substituted with Mn.
(4) When fluorine is added to Reference Example 7 as in Reference Examples 10 and 11, the discharge capacity is improved.

Claims (4)

A method for producing a spinel-type lithium-manganese composite oxide used as a positive electrode active material of a lithium ion secondary battery,
(I) a lithium compound, (ii) electrolytic manganese dioxide, (iii) Mg, at least one selected from at least one metal (M1) magnesium oxide and alumina a compound of selected from Al, and (iv) Boric acid , a compound of boron (M2),
The atomic ratio of Li: Mn: M1: M2 is (x + y) :( 2-ypq): p: q (where 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1 0.0 <x + y ≦ 1.2, 0 <p ≦ 1.0, 0.0005 ≦ q ≦ 0.1) to prepare an aqueous suspension,
A method for producing a spinel-type lithium-manganese composite oxide, comprising drying the aqueous suspension and then firing at a temperature of 650 to 900 ° C.   The method for producing a spinel-type lithium-manganese composite oxide according to claim 1, wherein the lithium compound is at least one selected from lithium hydroxide, lithium carbonate, and lithium nitrate.   The method for producing a spinel-type lithium-manganese composite oxide according to claim 1 or 2, wherein the solid content contained in the aqueous suspension is pulverized.   The method for producing a spinel-type lithium-manganese composite oxide according to any one of claims 1 to 3, wherein an average particle size of solids contained in the aqueous suspension is 0.1 to 5 µm.