JP5199522B2 - Spinel-type lithium / manganese composite oxide, its production method and use - Google Patents

Description

【００６７】
【実施例１２】
実施例１〜１１で得られた結晶性リチウム・マンガン複合酸化物を正極活物質として含む正極を用いて試験用リチウムイオン電池を作成し、電池性能を評価した。
まず、それぞれの結晶性リチウム・マンガン複合酸化物の微粒子と導電材としてのアセチレンブラックおよびバインダーとしてのポリ四フッ化エチレンパウダーを、７５：２０：５の重量比で混合し、乳鉢で混練して正極用合剤を調製した。この合剤を展伸ローラーで厚さ０．１mmのシートとし、１６mmφに型抜きした後１１０℃で真空乾燥して試験用正極を作成した。
【００６８】
これらの正極と金属リチウム箔（厚さ０．２μｍ）を、セパレーター（商品名：セルガード）を介してコイン型電池ケースに積層し、体積比１：１のエチレンカーボネートとジメチルカーボネート混合溶媒に１mol／lのＬiＰＦ₆を溶解した電解液を注入して試験用電池を作成した。
上記の電池について、放電容量、高温サイクル特性および高温劣化試験を行った。
（１）放電容量
定電流で０．５ｍＡ／cm²の電流密度、充電電位４．３Ｖまで、放電電位３．０Ｖまでの電位規制の条件で、まず重量当たりの放電容量を測定したのち、次式により体積当たりの放電容量を算出した。
【００６９】
体積当たりの放電容量＝重量当たりの放電容量×充填密度
（２）高温サイクル特性
試験用電池を６０℃の恒温槽に設置し、上記と同一の条件で３０回の充放電試験を行い、高温サイクル特性を次式の容量維持率で評価した。
容量維持率（％）＝
（１回目の重量当たり放電容量／３０回目の重量当たり放電容量）×１００
（３）高温劣化試験（高温保存性の評価）
高温の電解液中に一定時間浸したあとの正極活物質の性能劣化を放電容量の回復率を指標として評価した。
【００７０】
まず、正極活物質試料を１１０℃で３時間乾燥後、その約１０ｇを容積５０mlのふた付ステンレス製容器に採取した。これを露点約−７０℃のアルゴンガス循環グローブボックス内に移し、体積比１：１のエチレンカーボネートとジメチルカーボネート混合溶媒に１mol／lのＬiＰＦ₆を溶解した有機溶媒１０mlを加えた。容器を密閉後グローブボックスから取り出し、８５℃に設定された恒温槽に移し、７日間保持した。次いで容器を取り出し室温まで冷却後、容器内の試料と有機溶媒とを濾別し、１１０℃で３時間乾燥した。
【００７１】
こうして処理された正極活物質を用いて、上記同様の試験用正極および試験用電池を作成した。
これらの試験用電極の充放電試験を上記した条件で行い、次式により回復率を算出した。
Ａ：処理後の正極活物質を用いた電池の放電容量
Ｂ：未処理の正極活物質を用いた電池の放電容量
回復率（％）＝（Ａ／Ｂ）×１００
（なお、放電容量は２サイクル目の値）
上記で得られた放電容量、高温サイクル特性および回復率の結果を表２に示す。
【００７２】
【比較例５】
比較例１〜４で得られた結晶性リチウム・マンガン複合酸化物を正極活物質として含む正極を用いて、実施例１２と同様にして試験用リチウムイオン電池を作成し、電池性能を評価した。
結果を表２に示す。
【００７３】
【表２】

【００７４】
以上の実施例および比較例から、以下のことがわかる。
(1)硼素添加の有無以外は同一組成の実施例２と比較例１とを比べると、実施例２の方が、比表面積が小さく、充填密度も大きい。したがって、容量維持率、回復率ともに比較例１に比べて優れている。
(2)置換金属M1の有無以外は同一組成の実施例１と比較例２と比べると、実施例１の方が、容量維持率、回復率ともに優れている。
(3) 比較例３のようにリチウムが理論量(1.0)の場合は、リチウムが1.0以上でＭｎと置換している各実施例と比べて、容量維持率が劣る。
(4)実施例１０および１１のように、実施例７にフッ素を添加すると、放電容量が向上する。[0001]
TECHNICAL FIELD OF THE INVENTION
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.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
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.
[0003]
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.
[0004]
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 is proposed in which a part of manganese of lithium manganate is replaced with a metal element such as Al, Ni, Co, Fe, Cr, Ta, V, Ti, Mg, etc. No. 2-235858, JP-A-4-141945, JP-A-6-187993, JP-A-9-147867). In addition, lithium-manganese composite oxides in which a part of manganese is substituted with boron have been proposed (see Japanese Patent Laid-Open Nos. 4-237970, 8-79215, and 8-195200).
[0005]
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.
[0006]
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.
[0007]
OBJECT OF THE INVENTION
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.
[0008]
Summary of the Invention
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_pM2_qO_(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 0.1 to 2.0 m.²/ G is preferable.
[0009]
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,
Li: Mn: M₁: M₂: F atomic ratio is (x + y) :( 2-yp-q): 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.
[0010]
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.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
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_pM2_qO_(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)
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.
[0012]
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.
[0013]
As the element M2 whose oxide has a melting point of 800 ° C. or lower, specifically, B (B₂O_ThreeMelting point 460 ° C.), P (P₂O_FiveMelting point 420 ° C.), Pb (PbO; melting point 290 ° C.), Sb (Sb₂O_ThreeMelting point 655 ° C.), V (V₂O_FiveA melting point of 680 ° C.). 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.
[0014]
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.
[0015]
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.
[0016]
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. Secondary particles having a specific surface area of 0.1 to 2.0 m.²/ G, preferably 0.2 to 0.8 m²The packing density is in the range of 1.5 to 2.5 g / ml.
[0017]
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.
[0018]
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 cycling characteristics at high temperature can be aimed at.
[0019]
The specific surface area is 0.1m²If it is less than / g, the amount of dissolved Mn 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. 2.0m²If it exceeds / 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.
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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. .
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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, the specific surface area is 0.1 to 2.0 m by appropriately selecting the firing temperature according to the amount of the element M2.²Lithium / manganese composite oxide in the range of / g can be obtained.
[0031]
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.
[0032]
【Effect of the invention】
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.
[0033]
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.
[0034]
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.
[0035]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples at all.
[0036]
[Example 1]
Electrolytic manganese dioxide powder (γ-MnO₂, Purity 92%) and cobalt carbonate powder (CoCO_Three, Purity 93%) was charged into a wet pulverizer at a ratio of Mn: Co = 90: 10 (atomic ratio) and pulverized to an average particle size of 0.5 μm. 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.
[0037]
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, whereby Li_1.1Co_0.189Mn_1.701B_0.0095O_FourCrystalline lithium / manganese composite oxide fine particles having a composition of (x = 1.0, y = 0.1) were obtained.
[0038]
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 diameter: Laser diffraction / scattering particle size distribution analyzer (Horiba, LA-700)
Specific surface area: Automatic surface area measuring device (manufactured by Yuasa Ionics, Multi Soap-12)
Packing density: 25 g of a sample was taken into a 50 ml graduated cylinder, tapped on a wooden table for 3 minutes, its volume (V) was measured, and the following formula was obtained.
[0039]
Packing density (g / ml) = 25 / V
[0040]
[Example 2]
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 Li under the same synthesis conditions as_1.1Co_0.095Mn_1.796B_0.0095O_FourCrystalline lithium / manganese composite oxide fine particles (x = 1.0, y = 0.1) were prepared.
[0041]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0042]
[Example 3]
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 Under similar synthesis conditions, Li_1.1Co_0.019Mn_1.872B_0.0095O_FourCrystalline lithium / manganese composite oxide fine particles (x = 1.0, y = 0.1) were prepared.
[0043]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0044]
[Example 4]
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 similar synthesis conditions, Li_1.1Co_0.092Mn_1.751B_0.057O_FourCrystalline lithium / manganese composite oxide fine particles (x = 1.0, y = 0.1) were prepared.
[0045]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0046]
[Example 5]
Γ-Al as an aluminum compound₂O_Three(Purity: 95%) and the raw materials are blended so that the atomic ratio of lithium, aluminum, manganese and boron is Li: Al: Mn: B = 1.1: 0.095: 1.796: 0.0095 Except for the above, under the same synthesis conditions as in Example 1, Li_1.1Al_0.095Mn_1.796B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0047]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0048]
[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 under the same synthesis conditions as in Example 1 except that the raw materials were blended so as to be 0.0095_1.1Mg_0.047Mn_1.843B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0049]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0050]
[Example 7]
Nickel hydroxide (Ni (OH) as a nickel compound₂, Purity: 100%). 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 Under similar synthesis conditions, Li_1.1Ni_0.095Mn_1.796B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0051]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0052]
[Example 8]
Chromium anhydride (CrO_Three, Purity: 99.8%), and the atomic ratio of lithium, chromium, manganese and boron is Li: Cr: Mn: B = 1.1: 0.095: 1.796: 0.0095 With the same synthesis conditions as in Example 1 except that the raw materials were blended, Li_1.1Cr_0.095Mn_1.796B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0053]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0054]
[Example 9]
Iron oxide (Fe₂O_Three, Purity: 98%), and the atomic ratio of lithium, iron, manganese, and boron is Li: Fe: Mn: B = 1.1: 0.047: 1.843: 0.0095 Except for blending, under the same synthesis conditions as in Example 1, Li_1.1Fe_0.047Mn_1.843B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0055]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0056]
[Example 10]
Electrolytic manganese dioxide powder (γ-MnO₂, Purity 92%) and nickel hydroxide powder (Ni (OH)₂, Purity 100%) was charged into a wet pulverizer at a ratio of Mn: Ni = 95: 5 (atomic ratio) and pulverized 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.
[0057]
This slurry was dried with a spray dryer under the same conditions as in Example 1. Next, the dried powder is calcined at 850 ° C. for 6 hours under air flow, whereby Li_1.1Ni_0.095Mn_1.796B_0.0095O_3.905F_0.095Crystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0058]
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 Under the same synthesis conditions as in Example 10, Li_1.1Ni_0.095Mn_1.796B_0.0095O_3.81F_0.19Crystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0059]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0060]
[Comparative Example 1]
Li was the same as in Example 1 except that no boron was added and the amounts of lithium and cobalt were the same as in Example 2._1.1Co_0.095Mn_1.805O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0061]
[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 Example 1 were used except for Li and B. Li without substitution elements_1.1Mn_1.89B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0062]
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0063]
[Comparative Example 3]
Under the same synthesis conditions as in Example 1, except that Li is the theoretical amount and the substitution amounts of Co and B are the same as in Example 2, Li_1.0Co_0.10Mn_1.89B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0) were obtained.
Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0064]
[Comparative Example 4]
  The powders of electrolytic manganese dioxide, cobalt carbonate, lithium hydroxide and boric acid used in 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. The mixture is then calcined at 850 ° C. for 6 hours under air flow._1.1Co_0.095Mn_1.796B_0.0095O_FourCrystalline lithium / manganese composite oxide particles (x = 1.0, y = 0.1) were obtained.
[0065]
  Table 1 shows the average particle diameter, specific surface area, and packing density of the obtained fine particles.
[0066]
[Table 1]

[0067]
Example 12
Test lithium ion batteries were prepared using the positive electrodes containing the crystalline lithium / manganese composite oxides obtained in Examples 1 to 11 as the positive electrode active material, and the battery performance was evaluated.
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.
[0068]
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. l LiPF₆A battery for test was prepared by injecting an electrolytic solution in which the solution was dissolved.
The above battery was subjected to discharge capacity, high temperature cycle characteristics, and high temperature deterioration test.
(1) Discharge capacity
0.5mA / cm at constant current²First, the discharge capacity per weight was measured under the conditions of potential regulation up to the current density, charge potential 4.3V, and discharge potential 3.0V, and then the discharge capacity per volume was calculated according to the following equation.
[0069]
Discharge capacity per volume = discharge capacity per weight x packing density
(2) High temperature cycle characteristics
The test battery was placed in a constant temperature bath at 60 ° C., 30 charge / discharge tests were performed under the same conditions as described above, and the high temperature cycle characteristics were evaluated by the capacity retention rate of the following equation.
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.
[0070]
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 1 mol / l LiPF in a 1: 1 volume ratio of ethylene carbonate and dimethyl carbonate mixed solvent.₆10 ml of an organic solvent in which was dissolved 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.
[0071]
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 positive electrode active material after treatment
B: Discharge capacity of battery using untreated positive electrode active material
Recovery rate (%) = (A / B) × 100
(The discharge capacity is the value at the second cycle)
Table 2 shows the results of the discharge capacity, high-temperature cycle characteristics and recovery rate obtained above.
[0072]
[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.
[0073]
[Table 2]

[0074]
The following can be understood from the above examples and comparative examples.
(1) Comparing Example 2 and Comparative Example 1 having the same composition except for the presence or absence of boron addition, 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 with Example 1 and Comparative Example 2 having the same composition except for the presence or absence of the substitution metal M1, 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 Mn is substituted.
(4) As in Examples 10 and 11, when fluorine is added to Example 7, the discharge capacity is improved.

Claims (4)

Represented by the following general formula, the positive electrode active used as substances that spinel-type lithium-manganese composite oxide of the lithium ion secondary battery.
Li _{(x + y)} Mn _(2-ypq) M1 _p M2 _q O ₄
(In the formula, 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <x + y ≦ 1.2, 0 <p ≦ 1.0, 0.0005 ≦ q ≦ 0.1, M1: At least one metal selected from Mg and Al, M2: B (boron). ^{2. The} spinel-type lithium-manganese composite oxide used as a positive electrode active material of a lithium ion secondary battery according to claim 1, wherein the specific surface area is in the range of 0.1 to 2.0 m ² / g. (I) a lithium compound, (ii) a manganese compound, (iii) a compound of at least one metal (M1) selected from Mg, Al, (iv) a compound of boron (M2), Li: Mn: M1: M2 The atomic ratio is (x + y) :( 2-ypq): p: q (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) to prepare an aqueous suspension, and after drying the aqueous suspension, at a temperature of 650 to 900 ° C. A method for producing a spinel type lithium / manganese composite oxide used as a positive electrode active material of a lithium ion secondary battery , characterized by firing.   The lithium ion secondary battery which has a positive electrode containing the spinel type lithium manganese composite oxide of Claim 1 as a positive electrode active material.