JP2004303710A - Positive electrode active material for non-aqueous electrolyte secondary battery and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a non-aqueous electrolyte secondary battery, having excellent flatness in charge/discharge potential, high tapping density for obtaining an Li ion secondary battery with high discharge capacity, and a single phase spinel crystal structure. <P>SOLUTION: A manufacturing method of a LiMnNi composite oxide of a spinel structure represented by a general formula: Li<SB>(1+X)</SB>Mn<SB>(2-Y-X)</SB>Ni<SB>Y</SB>O<SB>4</SB>, where X is -0.05≤X≤0.10, and Y is 0.45≤Y≤0.55, is provided. The method comprises a step of adding manganese salt and nickel salt into a solvent so as to obtain the atomic ratio of Mn and Ni in the general formula, crushing and mixing them until the average particle diameter becomes 0.1μm or smaller, and spray-drying the resulted slurry to obtain a mixture of Mn salt and Ni salt, a step of sintering the mixture at 800-1,000°C to obtain a MnNi composite oxide, a step of adjusting the MnNi composite oxide so that the ratio of the total mol number of Mn and Ni and the mol number of Li is 2:0.95-1.10, and a step of sintering the mixture at 600-750°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０１１４】
図５から明らかなように、実施例１との比較において、比較例１〜３は、放電曲線において、３．５〜４Ｖ付近の低電位領域の棚が出現している。これは、比較例１〜３が、図２〜４に示すようにスピネル構造単相でないためであると考えられる。
【０１１５】
一方、実施例は、タップ密度が１．５ｇ／ｃｍ^３ 以上あることから電池としての体積エネルギー密度の上昇が見込まれ、また、比表面積についても、実施例は比較例と比べ低比表面積を実現できており、これによってリチウムマンガン複合酸化物特有の高温時の特性劣化を防ぐ効果を確保しつつ、図５の実施例１の放電曲線で例示されるように、４．５Ｖを超える領域が１２０ｍＡｈ／ｇ以上あり、かつ、３．５〜４Ｖ付近の低電位領域の棚は出現していないという従来と比較した優位性が示されているといえる。
【０１１６】
【発明の効果】
本発明によって得られるスピネル型リチウム複合酸化物は、一般式Ｌｉ_{（１＋Ｘ）}Ｍｎ_{（２−Ｙ−Ｘ）} Ｎｉ_Ｙ Ｏ_４ （ただし、式中Ｘ、Ｙは、各々−０．０５≦Ｘ≦０．１０、０．４５≦Ｙ≦０．５５）で表されるスピネル構造を有するリチウムマンガンニッケル複合酸化物の製造方法において、マンガン塩とニッケル塩を、上記一般式のマンガンとニッケルの原子比となるよう溶媒中に投入し、平均粒径が０．１μｍ以下に粉砕混合し、得られたスラリーを噴霧乾燥させてマンガン塩とニッケル塩の混合物を得る第１工程と、前記混合物を８００〜１０００℃で焼成してマンガンとニッケルの複合酸化物を得る第２工程と、第２工程で得られた複合酸化物とリチウム化合物を、マンガンとニッケルの合計のモル数とリチウムのモル数の比が実質的に２：０．９５〜１．１０となるように調整した混合物を６００〜７５０℃で焼成する第３工程、を有する製造方法を用いて得られる複合酸化物であり、スピネル型結晶構造単一相で、結晶欠陥のないリチウムマンガンニッケル複合酸化物が得られる。このことにより、タップ密度が高いことを維持しつつ、かつ、放電曲線において、３．５〜４Ｖ付近の低電位領域の棚は出現しない、高電位領域での電位平坦性にも優れた、放電容量が大きく、かつ、高エネルギー密度の非水系電解質二次電池を実現できるという効果を有する。
【図面の簡単な説明】
【図１】本発明の実施例１の方法によって得られたリチウムニッケルマンガン複合酸化物の乾燥粉末のＸ線回折図である。
【図２】比較例１の方法によって得られたリチウムニッケルマンガン複合酸化物の乾燥粉末のＸ線回折図である。
【図３】比較例２の方法によって得られたリチウムニッケルマンガン複合酸化物の乾燥粉末のＸ線回折図である。
【図４】比較例３の方法によって得られたリチウムニッケルマンガン複合酸化物の乾燥粉末のＸ線回折図である。
【図５】実施例および比較例１〜３における充放電試験の結果を示す図である。
【図６】充放電試験を行う際に用いたコイン電池の構造を示す図である。
【図７】（ａ）および（ｂ）は、実施例１のスプレードライヤーで噴霧乾燥後焼成したマンガンニッケル複合酸化物（ａ）と合成後のスピネル型リチウムマンガンニッケル複合酸化物（ｂ）のＳＥＭ写真像であり、（ｃ）〜（ｅ）は、順に比較例１〜３それぞれのリチウムマンガンニッケル複合酸化物のＳＥＭ写真像である。
【符号の説明】
１ リチウム金属負極
２ セパレータ（電解液含浸）
３ 正極（評価用電極）
４ ガスケット
５ 負極缶
６ 正極缶
７ 集電体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a positive electrode for a non-aqueous secondary battery using the same. More specifically, the present invention has a high tap density (powder packing density) and substantially no foreign phase. The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery having a spinel type crystal structure and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the spread of portable devices such as a mobile phone and a notebook computer, a demand for a small and lightweight secondary battery having a high energy density is increasing. As such a device, there is a non-aqueous electrolyte type lithium ion secondary battery, and research and development thereof have been actively carried out and its practical use has been attempted. This lithium ion secondary battery uses a positive electrode containing a lithium-containing composite oxide as an active material, and a material capable of occluding and releasing lithium, such as lithium, a lithium alloy, a metal oxide, or carbon, as an active material. The main components are a negative electrode to be used and a separator or a solid electrolyte containing a non-aqueous electrolyte.
[0003]
Among these components, those considered as a positive electrode active material include a lithium cobalt composite oxide (LiCoO ₂ ), Lithium nickel composite oxide (LiNiO) ₂ ), Lithium manganese composite oxide (LiMn) ₂ O ₄ ). In particular, with regard to batteries using lithium-cobalt composite oxide for the positive electrode, many developments have been made to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained, and commercialization has been achieved. Has reached.
[0004]
However, the demand for higher energy density for secondary batteries is increasing year by year, and lithium-ion secondary batteries using lithium-cobalt composite oxides, which are currently in practical use, for the positive electrode are expensive because cobalt is a scarce resource. For this reason, there is a need for an alternative material that is less expensive than cobalt and can achieve a high energy density.
[0005]
Therefore, LiCoO 2 is used as a positive electrode active material for a non-aqueous electrolyte secondary battery. ₂ Instead, lithium manganese oxide-based materials having a spinel-type crystal structure have attracted attention. Lithium manganese oxide having this spinel structure has Li ₂ Mn ₄ O ₉ , Li ₄ Mn ₅ O ₁₂ , LiMn ₂ O ₄ Among them, among them, LiMn ₂ O ₄ However, since charging and discharging can be performed in a 4 V region with respect to the Li (lithium) potential, active research has been made (Japanese Patent Application Laid-Open Nos. 6-76824, 7-73883, 7-83). -230802, JP-A-7-245106, etc.).
[0006]
Incidentally, in order to increase the energy density of a battery, one method is to use a positive electrode active material having a high potential, and a high voltage of 300 V or more is required as a power supply for an electric vehicle. LiCoO ₂ In the case where is used as a positive electrode active material, since the operating voltage is about 4.2 V, there is a problem that the number of connected batteries increases. Therefore, LiCoO ₂ Although it is required to use a positive electrode active material with a higher voltage, the spinel-type lithium manganese oxide has a working voltage of 4 V or less. ₂ In addition to having a smaller capacity than in the case of using ₂ There is a problem that the number is further increased than in the case of using.
[0007]
For this reason, higher voltage is being studied for spinel-type lithium manganese oxide. For example, it has been confirmed that a composite lithium manganese composite oxide in which manganese sites are replaced with nickel can obtain an operating voltage of 4.5 V or more based on the potential of metallic lithium (Japanese Patent Application Laid-Open No. 9-147867; Japanese Unexamined Patent Publication No. Hei 11-73962).
[0008]
However, the above materials are relatively difficult to synthesize, and it has been difficult to achieve both a single phase of spinel structure and a high tap density by conventional synthesis methods. For example, by using a method such as pulverization and mixing in which solid solution of manganese and nickel proceeds sufficiently, a single phase of spinel structure can be realized, but the particle diameter becomes small and handling becomes difficult, and the composite after synthesis becomes complex. High tap densities cannot be achieved with oxides. On the other hand, if a simple solid-phase method is used to synthesize a composite oxide with a high packing density and a moderately sized particle size that is easy to handle, the solid solution of manganese and nickel becomes insufficient. As a result, a hetero phase such as nickel oxide is generated, and a single phase having a spinel structure cannot be realized. As a result, in the discharge curve, the capacity in the high potential region of 4.8 V is reduced, the flatness of the potential is lost, the shelf in the low potential region around 4 V appears, and the positive electrode material does not have a high energy density. In addition, there is a problem that generation of gas at a high temperature is remarkable.
[0009]
Therefore, attention has been paid to uniform mixing in a liquid-liquid mixture system represented by a complex polymerization method or the like as disclosed in JP-A-2001-185148. In addition, the positive electrode active material particles have a problem that the particle diameter is very fine and only those having a low tap density can be obtained. In the discharge curve (voltage-capacity) shown in the drawings of this publication, a flat region exceeding 4.5 V was obtained up to 120 mAh / g, but a shelf appeared in a 4.0 V region in the lower part of the discharge curve. I have.
[0010]
Japanese Patent Application Laid-Open No. 2001-146426 discloses a method in which a compound of lithium, manganese, and nickel is pulverized and mixed by a wet method, and the obtained slurry is spray-dried. Disturbs the dispersion of manganese and nickel, so that uniform solid solution does not progress. As a result, there remains a problem that a low potential region shelf around 4 V appears on the discharge curve.
[0011]
Further, JP-A-2001-143704 discloses that a manganese compound and a metal M (M is nickel or nickel as essential components, and one or more metals selected from aluminum or a transition metal element are added thereto. A method is disclosed in which the compound of Example 1 is heat-treated in advance and then heat-treated with a lithium compound. However, in the discharge curve (voltage-capacity) shown in the drawings of this publication, a flat region exceeding 4.5 V has a flat area of 120 mAh / g, but a shelf appears in the 4.0 V region in the falling part of the discharge curve.
[0012]
[Patent Document 1]
JP-A-6-76824
[0013]
[Patent Document 2]
JP-A-7-73883
[0014]
[Patent Document 3]
JP-A-7-230802
[0015]
[Patent Document 4]
JP-A-7-245106
[0016]
[Patent Document 5]
JP-A-9-147867
[0017]
[Patent Document 6]
JP-A-11-73962
[0018]
[Patent Document 7]
JP 2001-185148 A
[0019]
[Patent Document 8]
JP 2001-146426 A
[0020]
[Patent Document 9]
JP 2001-143704 A
[0021]
[Problems to be solved by the invention]
In the present invention, a positive electrode active material for a non-aqueous electrolyte secondary battery having a spinel type crystal structure having a high tap density, a uniform solid solution of manganese and nickel and substantially no different phases, and a method for producing the same are provided. As a result, it is an object of the present invention to provide a lithium ion secondary battery having excellent charge / discharge potential flatness and a large discharge capacity.
[0022]
[Means for Solving the Problems]
The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a general formula Li _{(1 + X)} Mn _(2-YX) Ni _Y O ₄ (Where X and Y are -0.05 ≦ X ≦ 0.10 and 0.45 ≦ Y ≦ 0.55, respectively), which is a lithium manganese nickel composite oxide having a spinel structure, The cubic unit cell has a lattice constant of 8.17 to 8.18 ° and a specific surface area of 0.2 to 1.0 m. ² / G and tap density of 1.52 g / cm ³ This is characterized in that a region exceeding 4.5 V in the discharge curve is 120 mAh / g or more, and a shelf in a potential region of 3.5 to 4.5 V is excluded. Here, the shelf refers to a potential step in the 4V region that appears at the falling part of the discharge curve.
[0023]
Further, the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention comprises a general formula Li having the above characteristics. _{(1 + X)} Mn _(2-YX) Ni _Y O ₄ (Where X and Y are -0.05 ≦ X ≦ 0.10 and 0.45 ≦ Y ≦ 0.55, respectively) In the method for producing a lithium manganese nickel composite oxide having a spinel structure represented by: , A manganese salt and a nickel salt are charged into a solvent so that the manganese and nickel have the atomic ratio of manganese and nickel in the above general formula. A first step of obtaining a mixture of a salt and a nickel salt, a second step of firing the mixture at 800 to 1000 ° C. to obtain a composite oxide of manganese and nickel, and a composite oxide and lithium obtained in the second step. A third step of firing a mixture at 600 to 750 ° C., wherein the mixture is prepared by adjusting the compound so that the ratio of the total number of moles of manganese and nickel to the number of moles of lithium is substantially 2: 0.95 to 1.10. Consisting of The features.
[0024]
The firing temperature of the mixture of the manganese salt and the nickel salt is preferably 800 ° C. or more and less than 900 ° C.
[0025]
As the manganese salt, it is preferable to use at least one selected from manganese carbonate, manganese carbonate hydrate, manganese hydroxide, and manganese oxyhydroxide. Further, as the nickel salt, it is preferable to use at least one selected from nickel carbonate, nickel carbonate hydrate, nickel hydroxide, and nickel oxyhydroxide.
[0026]
Further, it is preferable that the manganese salt and the nickel salt are pulverized and mixed using a wet pulverizer.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors have produced a composite lithium manganese composite oxide in which manganese sites having a spinel structure, which is a positive electrode active material for a non-aqueous electrolyte secondary battery, are replaced with nickel by a conventional solid-phase method. The cause of the appearance of a shelf in a low potential region near 4 V in the discharge curve, which is considered to be caused by the oxidation reduction of Mn without replacing Ni to 0.5, is due to the non-uniformity of solid solution of manganese and nickel. I found something.
[0028]
Therefore, the solid-phase method that easily obtains powder properties with a high tap density is examined in detail, and before mixing the lithium compound, the manganese raw material and the metal salt of the nickel raw material are finely pulverized and mixed to a nanoscale, and then 800 ° C. The inventors have found that the above problem can be solved by baking as described above to synthesize a manganese-nickel composite oxide uniformly dissolved, and then mixing and baking a lithium compound, thereby leading to the present invention.
[0029]
In the present invention, specifically, the general formula Li _{(1 + X)} Mn _(2-YX) Ni _Y O ₄ (Where X and Y are -0.05 ≦ X ≦ 0.10 and 0.45 ≦ Y ≦ 0.55, respectively) In the method for producing a lithium manganese nickel composite oxide having a spinel structure represented by: , A manganese salt and a nickel salt are introduced into a solvent so as to have an atomic ratio of manganese and nickel represented by the above general formula, and pulverized and mixed to an average particle size of 0.1 μm or less. A first step of obtaining a mixture of a salt and a nickel salt, a second step of firing the mixture at 800 to 1000 ° C. to obtain a composite oxide of manganese and nickel, and a composite oxide and lithium obtained in the second step. A third step of calcining the compound at 600 to 750 ° C., wherein the mixture is prepared by adjusting the compound so that the ratio of the total number of moles of manganese and nickel to the number of moles of lithium is substantially 2: 0.95 to 1.10. Through Producing a positive active material for a non-aqueous electrolyte secondary battery.
[0030]
In synthesizing the spinel-type lithium nickel manganese composite oxide, at least one selected from manganese carbonate, manganese carbonate hydrate, manganese hydroxide, and manganese oxyhydroxide can be used as the manganese salt. As the nickel salt, at least one selected from nickel carbonate, nickel carbonate hydrate, nickel hydroxide, and nickel oxyhydroxide can be used. On the other hand, as a lithium raw material, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate and the like can be used.
[0031]
A manganese salt and a nickel salt are introduced into a solvent such as pure water, ethanol, or acetone so that the manganese and nickel have the atomic ratio of manganese and nickel in the above general formula, and the average particle size of the manganese salt and the nickel salt is 0.1 μm or less. And pulverize and mix. For pulverization and mixing, a wet fine pulverizer such as a bead mill, an airflow impact pulverizer such as a ball mill, and a jet mill are used. In order to disperse manganese and nickel more uniformly, it is preferable to use a bead mill.
[0032]
If the average particle size exceeds 0.1 μm, even if mixing is performed in a later step, the solid solution of manganese and nickel becomes insufficient, and a hetero phase such as nickel oxide is generated, and as a result, the spinel structure Single phase cannot be realized.
[0033]
Thereafter, the obtained slurry is spray-dried using a spray dryer to obtain a mixed granulated product of a manganese salt and a nickel salt. When the mixed powder is directly dried without being subjected to this step and mixed with a lithium salt to synthesize lithium manganese oxide, the synthesis proceeds in a state in which the fine powder is aggregated, so that irregularly shaped aggregated secondary particles increase. In addition, many fine powders are present around the secondary particles, and powder characteristics with a high tap density cannot be obtained.
[0034]
As in the present invention, when the obtained slurry is spray-dried using a spray drier to obtain a mixed granulated product of a manganese salt and a nickel salt, the granulated product has a spherical shape or an ellipsoid close to a spherical shape. First, relatively dense particles are obtained as secondary particles in which primary particles are gathered. The average particle size of such a granulated product is preferably 3 to 20 μm. Outside this range, powder properties with a high tap density cannot be obtained.
[0035]
Next, the mixture is baked at 800 to 1000 ° C. for about 2 to 20 hours in an oxygen or air atmosphere to obtain a composite oxide of manganese and nickel. It is more preferable that the firing temperature is at least 800 ° C and less than 900 ° C. Uniform dispersion and solid solution of manganese and nickel are promoted by setting the firing temperature to 800 ° C. or higher, but if the firing temperature is lower than 800 ° C., manganese and nickel are not completely oxidized and solid solution does not proceed. Will be. On the other hand, it is necessary to consider energy costs industrially. It has been confirmed that there is no problem in the uniform solid solution of manganese and nickel when the firing temperature is lower than 900 ° C, but no crystal growth is affected even when the firing temperature exceeds 1000 ° C. It is desirable to keep the temperature below 1000 ° C., and it is not preferable to exceed 1000 ° C.
[0036]
Next, the composite oxide of manganese and nickel and the lithium compound obtained in the firing step were mixed with the total molar number of manganese and nickel and the molar number of lithium to substantially 2: 0.95 to 1.10. Then, the mixture is mixed using a shaker mixer, a stirring mixer, a rocking mixer, or the like under relatively weak conditions such that the shape of the spherical secondary particles is maintained. The mixed powder is fired at 600 to 750 ° C. for 10 to 20 hours in an oxygen atmosphere or an air atmosphere to obtain a lithium nickel manganese composite compound.
[0037]
The crystal structure of the obtained lithium nickel manganese composite oxide needs to be cubic spinel. If the solid solution of manganese and nickel is insufficient, or if the composition deviates from the target composition, a hetero phase such as nickel oxide is generated, and a single phase of spinel structure cannot be realized. If the spinel structure is not a single phase, the capacity in the high potential region of 4.8 V decreases in the discharge curve, the flatness of the potential is lost, and a shelf in the low potential region of 4 V appears, and the positive electrode material having a high energy density is formed. In addition, a problem that gas generation at a high temperature is remarkable appears.
[0038]
When the ratio of the total number of moles of manganese and nickel to the number of moles of lithium deviates substantially from 2: 0.95 to 1.10 and the amount of lithium is small, NiO or the like may be used in addition to the spinel-type lithium nickel manganese composite oxide. When lithium content is high, lithium that cannot be dissolved completely remains on the surface of the lithium nickel manganese composite oxide, which deteriorates battery performance and causes gelation from reaction with the electrolytic solution. It is not preferable because it causes deterioration.
[0039]
On the other hand, if the firing temperature of the mixed powder of the composite oxide of manganese and nickel and the lithium compound is lower than 600 ° C., the solid solution of lithium is insufficient, which is not preferable. If it exceeds 750 ° C., oxygen deficiency occurs and the spinel structure is lost. Would.
[0040]
The spinel-type lithium nickel manganese composite oxide obtained by the above production method preferably has a lattice constant of a cubic unit cell of 8.17 to 8.18 °. The specific surface area of the composite oxide is 0.2 to 1.0 m. ² / G is desirable. Further, the tap density is 1.52 g / cm. ³ It is preferable that it is above. By satisfying these characteristics, a lithium-nickel-manganese composite oxide having a single phase with a spinel structure substantially free from a different phase and having a high tap density can be obtained. In a non-aqueous electrolyte secondary battery using this composite oxide as a positive electrode active material for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery having no shelf in a low potential region of 3.5 to 4.5 V in a discharge curve. A positive electrode active material for a secondary battery is obtained.
[0041]
A positive electrode using the composite oxide according to the present invention as a positive electrode active material is, for example, appropriately adding a conductive additive, a binder, and the like as necessary to the positive electrode active material, mixing the mixture, and forming a paste with a solvent (the binder is It may be previously dissolved in a solvent and then mixed with the positive electrode active material), and the obtained positive electrode mixture-containing paste is applied to a positive electrode current collector made of aluminum foil or the like, dried, and dried. And, if necessary, through a step of pressure molding. However, the method for manufacturing the positive electrode is not limited to the above-described example, and any method can be adopted.
[0042]
In producing the positive electrode, graphite (natural graphite, artificial graphite, expanded graphite, or the like), carbon black-based material such as acetylene black, Ketjen black, or the like can be used as the conductive additive. In addition, as the binder, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluoro rubber, styrene butadiene, cellulose resin, polyacrylic acid, or the like can be used.
[0043]
Examples of the active material of the negative electrode which is a counter electrode to the positive electrode containing the positive electrode active material include lithium, a lithium alloy represented by lithium-aluminum, graphite, pyrolytic carbons, cokes, glassy carbons, and organic materials. Carbon materials such as fired molecular compounds, mesocarbon microbeads, carbon fibers, activated carbon, etc., which can reversibly occlude and release lithium ions, alloys such as Si, Sn, In, etc., or oxidations that can be charged and discharged at a low potential close to Li Compounds such as materials and nitrides can also be used as the negative electrode active material.
[0044]
When the negative electrode active material is lithium or a lithium alloy, the negative electrode is used as it is, or is produced by press-bonding to a current collector.When the negative electrode active material is a carbon-based material, the negative electrode The same binder is added to the negative electrode active material and mixed, and the mixture is made into a paste using a solvent (the binder may be dissolved in a solvent in advance and then mixed with the negative electrode active material). The paste is prepared by applying the containing paste to a negative electrode current collector made of copper foil or the like, drying it to form a negative electrode mixture layer, and, if necessary, performing pressure molding. However, the method for manufacturing the negative electrode is not limited to the above-described example, and any method can be adopted.
[0045]
As the electrolyte, any of a non-aqueous liquid electrolyte and a gel polymer electrolyte can be used. In the present invention, a liquid electrolyte called an electrolyte is generally used frequently. This liquid electrolyte (electrolyte solution) is prepared by dissolving an electrolyte salt such as a lithium salt in a non-aqueous solvent containing an organic solvent as a main component. Examples of the solvent include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. , A chain ester such as methyl propionate, a chain phosphate triester such as trimethyl phosphate, 1,2-dimethoxyethane, 1,3-dioxolan, tetrahydrofuran, 2-methyl-tetrahydrofuran, diethyl ether and the like. it can. In addition, an amine imide organic solvent and a sulfur organic solvent such as sulfolane can also be used.
[0046]
Further, it is preferable to use an ester having a high dielectric constant (conductivity of 30 or more) as another solvent component from the viewpoint of improving battery characteristics, particularly load characteristics, and a specific example of the ester having a high dielectric constant is ethylene carbonate. , Propylene carbonate, butylene carbonate, γ-butyrolactone, and the like.Also, sulfur-based esters such as ethylene glycol sulfite can be used.Esters having a cyclic structure are preferable, and cyclic carbonates such as ethylene carbonate are particularly preferable. . These solvents can be used alone or in combination of two or more.
[0047]
As an electrolyte salt such as a lithium salt, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (Rf ₁ SO ₂ ) (Rf ₂ SO ₂ ) [Where Rf ₁ , Rf ₂ Is a substituent containing a fluoroalkyl group], LiN (Rf ₃ OSO ₂ ) (Rf ₄ OSO ₂ ) [Where Rf ₃ , Rf ₄ Is a fluoroalkyl group], LiC _n F _{2n + 1} SO ₃ (N ≧ 2), LiC (Rf ₅ SO ₂ ) ₂ , LiN (Rf ₆ OSO ₂ ) ₂ [Where Rf ₅ , Rf ₆ Is a fluoroalkyl group], and a polymer type imide lithium salt or the like is used alone or in combination of two or more. The concentration of the electrolyte salt in the electrolyte is not particularly limited, but is preferably 0.1 to 2.0 mol / l.
[0048]
The gel-like polymer electrolyte is equivalent to the above-mentioned electrolyte solution gelled with a gelling agent. In the gelation, for example, a linear polymer such as polyvinylidene fluoride, polyethylene oxide, or polyacrylonitrile or a linear polymer thereof is used. Copolymers, polyfunctional monomers that polymerize upon irradiation with actinic rays such as ultraviolet rays or electron beams (for example, tetrafunctional or higher such as pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, etc.) Acrylate and tetrafunctional or higher methacrylate similar to the above acrylate). However, in the case of a monomer, a polymer obtained by polymerizing the above-mentioned monomer acts as a gelling agent, instead of the monomer itself gelling the electrolytic solution.
[0049]
When gelling an electrolytic solution using a polyfunctional monomer as described above, if necessary, as a polymerization initiator, benzoyls, benzoin alkyl ethers, benzophenones, benzoylphenylphosphine oxides, acetophenones, thioxanthone , Anthraquinones, amino esters and the like can also be used.
[0050]
In the non-aqueous electrolyte secondary battery using the positive electrode active material obtained by the present invention, a non-aqueous electrolyte having a large discharge capacity, excellent flatness at a high potential, and a high energy density due to a high tap density. An electrolyte secondary battery becomes feasible.
[0051]
【Example】
(Example 1)
Commercially available manganese carbonate hexahydrate (MnCO ₃ ・ 6H ₂ O: Wako Pure Chemical Industries) and nickel hydroxide (Ni (OH) ₂ : Wako Pure Chemical Industries, Ltd.) was weighed so that the atomic ratio of Mn to Ni was 1.5: 0.5, and pure water was added thereto to prepare a slurry having a solid content concentration of 10% by weight. While stirring the slurry, the slurry was pulverized using a circulating medium stirring type wet pulverizer until the average particle diameter of the solid content in the slurry became 0.1 μm or less.
[0052]
Thereafter, spray drying was performed using a two-fluid nozzle spray type spray dryer (MDL-050-M, manufactured by Fujisaki Electric Co., Ltd.). The average particle size at this time was 8.5 μm. Further, firing was performed at 890 ° C. for 20 hours in an oxygen atmosphere to obtain a manganese nickel composite oxide. FIG. 7A shows an SEM photographic image of this manganese nickel composite oxide.
[0053]
Then, a commercially available lithium hydroxide monohydrate (LiOH. (H) is used so that Li: Mn: Ni = 1.0: 1.5: 0.5 (atomic ratio). ₂ O) (manufactured by FMC)) and the manganese nickel composite oxide were weighed, mixed with a shaker mixer for 10 minutes to such an extent that spherical secondary particles were maintained, and then at 700 ° C. for 20 hours in an oxygen atmosphere. Fired.
[0054]
As a result, the average particle diameter was about 13 μm and the specific surface area was 0.5 m. ² / G of substantially spherical secondary particles were obtained. The obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, and as shown in FIG. 1, it was confirmed to be a cubic spinel-type lithium manganese nickel composite oxide single phase. FIG. 7B shows an SEM photographic image of this powder.
[0055]
The particle size distribution was measured by a laser diffraction / scattering type particle size distribution analyzer (Microtrac HRA manufactured by Nikkiso Co., Ltd.). The measurement was performed using an X-ray diffractometer (RINT-1400 manufactured by Rigaku Corporation).
[0056]
12 g of this powder was placed in a 20 ml glass measuring cylinder, and after tapping 500 times, the powder packing density (tap density) was measured to be 1.58 g / cm. ³ Met.
[0057]
The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.173 °.
[0058]
Using the obtained active material, a battery was prepared as follows, and the charge / discharge capacity was measured.
[0059]
52.5 mg of the active material, 15 mg of acetylene black and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed and press-molded at a pressure of 100 MPa to a diameter of 11 mmφ.
[0060]
The prepared electrode was dried in a vacuum dryer at 120 ° C. overnight. The 2032 type coin battery shown in FIG. 6 was assembled in a glove box in an Ar atmosphere. For the negative electrode, Li metal having a diameter of 17 mm and a thickness of 1 mm was used, and for the electrolyte, 1M LiPF was used. ₆ A mixed solution of an equal amount of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) using as a supporting salt was used. A 25 μm-thick polyethylene porous film was used as the separator.
[0061]
The coin battery was left for about 10 hours after assembly, and after the open circuit voltage was stabilized, the current density was 0.5 mA / cm. ² The charge / discharge test was performed with the end voltages of charging and discharging of 4.9 V and 3.0 V, respectively. As a result, as shown in FIG. 5, in the discharge curve, a region exceeding 4.5 V was 120 mAh / g or more, and a shelf in a low potential region around 3.5 to 4 V did not appear.
[0062]
(Example 2)
Commercially available manganese carbonate hexahydrate (MnCO ₃ ・ 6H ₂ O: Wako Pure Chemical Industries) and nickel carbonate (NiCO ₃ : Manufactured by Wako Pure Chemical Industries, Ltd.), and a lithium manganese nickel composite oxide was obtained in the same manner as in Example 1, except that the sintering temperature for obtaining the manganese nickel composite oxide was 800 ° C.
[0063]
As a result, the average particle diameter was about 12 μm and the specific surface area was 0.8 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, it was confirmed that the powder was a cubic spinel-type lithium manganese nickel composite oxide single phase.
[0064]
When the tap density of the obtained powder was measured, it was 1.70 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.173 °. In addition, as a result of producing a battery using the obtained active material and performing a charge / discharge test, a region exceeding 4.5 V in the discharge curve was 120 mAh / g as in the case of the example 1 shown in FIG. Above, and no shelf in the low potential region around 3.5-4 V appeared.
[0065]
(Example 3)
Commercially available manganese hydroxide (Mn (OH) ₂ : Wako Pure Chemical Industries) and nickel hydroxide (Ni (OH) ₂ : Manufactured by Wako Pure Chemical Industries, Ltd.), and a lithium manganese nickel composite oxide was obtained in the same manner as in Example 1 except that the calcination temperature for obtaining the manganese nickel composite oxide was 1000 ° C.
[0066]
As a result, the average particle diameter was about 13.5 μm and the specific surface area was 0.4 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, it was confirmed that the powder was a cubic spinel-type lithium manganese nickel composite oxide single phase.
[0067]
When the tap density of the obtained powder was measured, it was 1.54 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.174 °. In addition, as a result of producing a battery using the obtained active material and performing a charge / discharge test, a region exceeding 4.5 V in the discharge curve was 120 mAh / g as in the case of the example 1 shown in FIG. Above, and no shelf in the low potential region around 3.5-4 V appeared.
[0068]
(Example 4)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the above-mentioned manganese nickel composite oxide, except that the mixture ratio was Li: Mn: Ni = 0.95: 1.5: 0.5 (atomic ratio). In the same manner as in the above, a lithium manganese nickel composite oxide was produced.
[0069]
As a result, the average particle diameter was about 13 μm and the specific surface area was 0.5 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, it was confirmed that the powder was a cubic spinel-type lithium manganese nickel composite oxide single phase.
[0070]
When the tap density of the obtained powder was measured, it was 1.56 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.170 °. In addition, as a result of producing a battery using the obtained active material and performing a charge / discharge test, a region exceeding 4.5 V in the discharge curve was 120 mAh / g as in the case of the example 1 shown in FIG. Above, and no shelf in the low potential region around 3.5-4 V appeared.
[0071]
(Example 5)
Lithium hydroxide monohydrate (LiOH. (H ₂ Example 1 except that the mixing ratio of O) (manufactured by FMC)) and the composite oxide of manganese nickel was set to Li: Mn: Ni = 1.10: 1.5: 0.5 (atomic ratio). In the same manner as in the above, a lithium manganese nickel composite oxide was produced.
[0072]
As a result, the average particle diameter was about 14 μm and the specific surface area was 0.5 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, it was confirmed that the powder was a cubic spinel-type lithium manganese nickel composite oxide single phase.
[0073]
When the tap density of the obtained powder was measured, it was 1.65 g / cm. ³ Met. The calculated lattice constant by Rietveld analysis of the X-ray diffraction pattern was 8.175 °. In addition, as a result of producing a battery using the obtained active material and performing a charge / discharge test, a region exceeding 4.5 V in the discharge curve was 120 mAh / g as in the case of the example 1 shown in FIG. Above, and no shelf in the low potential region around 3.5-4 V appeared.
[0074]
(Example 6)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the manganese nickel composite oxide were mixed, and a manganese-nickel composite oxide was produced in the same manner as in Example 1 except that the calcination temperature was set to 600 ° C.
[0075]
As a result, the average particle diameter was about 11 μm and the specific surface area was 0.7 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, it was confirmed that the powder was a cubic spinel-type lithium manganese nickel composite oxide single phase.
[0076]
When the tap density of the obtained powder was measured, it was 1.53 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.171 °. In addition, as a result of producing a battery using the obtained active material and performing a charge / discharge test, a region exceeding 4.5 V in the discharge curve was 120 mAh / g as in the case of the example 1 shown in FIG. Above, and no shelf in the low potential region around 3.5-4 V appeared.
[0077]
(Example 7)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the manganese nickel composite oxide were mixed, and a manganese nickel composite oxide was produced in the same manner as in Example 1 except that the firing temperature was 750 ° C.
[0078]
As a result, the average particle diameter was about 13 μm and the specific surface area was 0.4 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, it was confirmed that the powder was a cubic spinel-type lithium manganese nickel composite oxide single phase.
[0079]
When the packing density and tap density of the obtained powder were measured, the density was 1.66 g / cm. ³ Met. The calculated lattice constant by Rietveld analysis of the X-ray diffraction pattern was 8.175 °. In addition, as a result of producing a battery using the obtained active material and performing a charge / discharge test, a region exceeding 4.5 V in the discharge curve was 120 mAh / g as in the case of the example 1 shown in FIG. Above, and no shelf in the low potential region around 3.5-4 V appeared.
[0080]
(Comparative Example 1)
The calcination temperature for obtaining the manganese nickel composite oxide was 700 ° C., and the obtained spray-dried product and a commercially available lithium hydroxide monohydrate (LiOH · H ₂ O (manufactured by FMC)) was performed in the same manner as in Example 1 except that the atomic ratio of Li: Mn: Ni was 0.9: 1.5: 0.5 to obtain spherical secondary particles. The mixture was mixed for 10 minutes using a shaker mixer to the extent that the shape was maintained, and fired at 700 ° C. for 20 hours in an oxygen atmosphere. As a result, substantially spherical secondary particles having an average particle diameter of about 6 μm were obtained. FIG. 7C shows an SEM photographic image of this powder.
[0081]
The obtained fired product was analyzed by powder X-ray diffraction using Cu-Kα radiation. As shown in FIG. 2, in addition to the spinel-type lithium manganese nickel composite oxide having a cubic crystal, a hetero phase of NiO was observed. It could be confirmed. The tap density of this powder was 0.75 g / cm. ³ , Specific surface area is 12.4m ² / G, and the lattice constant was 8.174 °. In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, as shown in FIG. 5, a shelf in a low potential region around 3.5 to 4 V appeared in the discharge curve.
[0082]
(Comparative Example 2)
Commercially available lithium nitrate (LiNO ₃ : Kanto Chemical), manganese nitrate hexahydrate (Mn (NO ₃ ) ₂ ・ 6H ₂ O: Wako Pure Chemical Industries) and nickel nitrate hexahydrate (Ni (NO ₃ ) ₂ ・ 6H ₂ O: manufactured by Wako Pure Chemical Industries, Ltd.) was weighed so that the atomic ratio of Li: Mn: Ni was 1.0: 1.5: 0.5, and dissolved in 50 ml of pure water to obtain an aqueous solution. Then, 100 g of a 20% PVA solution was mixed with the mixture, and the mixture was heated and held by a hot stirrer, and the water was removed by heating at a temperature of about 150 to 200 ° C., whereby nitrate decomposition and polymer burning occurred. The generated heat causes a reaction between lithium ions, manganese ions, and nickel ions, resulting in spinel-type LiMn. _1.5 Ni _0.5 O ₄ Was obtained.
[0083]
The obtained precursor is calcined at 500 ° C. for 2 hours in a muffle furnace (model KDF HR7: manufactured by Denken), and then calcined at 600 ° C. for 20 hours in an oxygen atmosphere to obtain spinel-type LiMn. _1.5 Ni _0.5 O ₄ Was synthesized. As a result, foamed particles having an average particle diameter of about 24 μm were obtained. FIG. 7D shows an SEM photographic image of this powder.
[0084]
The obtained fired product was analyzed by powder X-ray diffraction using Cu-Kα radiation. As shown in FIG. 3, in addition to the spinel-type lithium manganese nickel composite oxide having a cubic crystal, a heterogeneous phase of NiO was observed. It could be confirmed. The tap density is 0.92 g / cm ³ , Specific surface area is 5.9m ² / G, and the lattice constant was 8.173 °. In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, as shown in FIG. 5, a shelf in a low potential region around 3.5 to 4 V appeared in the discharge curve.
[0085]
(Comparative Example 3)
Commercially available nickel sulfate hexahydrate (NiSO ₄ ・ 6H ₂ O: manufactured by Sumitomo Metal Mining), manganese sulfate pentahydrate (MnSO ₄ ・ 5H ₂ O: manufactured by Wako Pure Chemical Industries, Ltd.) was weighed such that the atomic ratio of Mn to Ni was 3: 1 and dissolved in pure water to prepare 300 cc of a 2 mol / l sulfate solution of Mn and Ni. Next, 400 cc of pure water was added to a 1-liter beaker, and then the temperature was raised to 60 ° C. while stirring, and then 25% caustic soda and the above-mentioned Mn, Ni sulfate solution were added so that the pH became constant at 11.0. And a composite hydroxide was obtained on nickel.
[0086]
After the completion of the addition of the Mn and Ni sulfate solutions, the composite hydroxide was filtered, washed with water, and vacuum-dried at 40 ° C. Then, a commercially available lithium hydroxide monohydrate (LiOH.H ₂ O (manufactured by FMC) is weighed so that the atomic ratio of Li: Mn: Ni is 1.0: 1.5: 0.5. Then, the mixture was mixed and baked at 600 ° C. for 20 hours in an oxygen atmosphere. As a result, secondary particles having an average particle diameter of about 4 μm having an irregular shape in which fine powder was aggregated were obtained. FIG. 7E shows an SEM photographic image of this powder.
[0087]
The obtained calcined product was analyzed by powder X-ray diffraction using Cu-Kα radiation. As shown in FIG. 4, in addition to the spinel-type lithium manganese nickel composite oxide having a cubic crystal, NiO, NiMnO ₃ Was confirmed. The tap density of this powder was 0.71 g / cm. ³ , Specific surface area is 18.9m ² / G, and the lattice constant was 8.173 °. In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, as shown in FIG. 5, a shelf in a low potential region around 3.5 to 4 V appeared in the discharge curve.
[0088]
(Comparative Example 4)
A lithium manganese nickel composite oxide was obtained in the same manner as in Example 1, except that the firing temperature at the time of obtaining the manganese nickel composite oxide was 750 ° C.
[0089]
As a result, the average particle diameter was about 10 μm, and the specific surface area was 4.4 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, NiO peak was confirmed in addition to the cubic spinel-type lithium manganese nickel composite oxide.
[0090]
When the tap density of the obtained powder was measured, it was 1.39 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.183 °.
[0091]
In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, a shelf in a low potential region around 3.5 to 4 V appeared in a discharge curve.
[0092]
(Comparative Example 5)
A lithium manganese nickel composite oxide was obtained in the same manner as in Example 1, except that the firing temperature at the time of obtaining the manganese nickel composite oxide was 1050 ° C.
[0093]
As a result, the average particle diameter was about 15 μm and the specific surface area was 0.5 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, NiO peak was confirmed in addition to the cubic spinel-type lithium manganese nickel composite oxide.
[0094]
When the tap density of the obtained powder was measured, it was 1.61 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.174 °.
[0095]
In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, a shelf in a low potential region around 3.5 to 4 V appeared in a discharge curve.
[0096]
(Comparative Example 6)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the composite oxide of manganese nickel, except that the mixing ratio was Li: Mn: Ni = 0.90: 1.5: 0.5 (atomic ratio). In the same manner as in Example 1, a lithium manganese nickel composite oxide was produced.
[0097]
As a result, the average particle diameter was about 10 μm and the specific surface area was 0.5 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, NiO peak was confirmed in addition to the cubic spinel-type lithium manganese nickel composite oxide.
[0098]
When the tap density of the obtained powder was measured, it was 1.53 g / cm. ³ Met. The calculated lattice constant by Rietveld analysis of the X-ray diffraction pattern was 8.176 °.
[0099]
In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, a shelf in a low potential region around 3.5 to 4 V appeared in a discharge curve.
[0100]
(Comparative Example 7)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the composite oxide of manganese nickel described above, except that the ratio of Li: Mn: Ni was 1.15: 1.5: 0.5 (atomic ratio). In the same manner as in Example 1, a lithium manganese nickel composite oxide was produced.
[0101]
As a result, the average particle diameter was about 14 μm and the specific surface area was 0.5 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, NiO peak was confirmed in addition to the cubic spinel-type lithium manganese nickel composite oxide.
[0102]
When the packing density (tap density) of the obtained powder was measured, it was 1.62 g / cm. ³ Met. The calculated lattice constant by Rietveld analysis of the X-ray diffraction pattern was 8.176 °.
[0103]
In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, a shelf in a low potential region around 3.5 to 4 V appeared in a discharge curve.
[0104]
(Comparative Example 8)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the manganese nickel composite oxide were mixed, and a lithium manganese nickel composite oxide was produced in the same manner as in Example 1 except that the firing temperature was 550 ° C.
[0105]
As a result, the average particle diameter was about 12 μm, and the specific surface area was 0.6 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα ray, NiO and NiMnO were used in addition to the cubic spinel-type lithium manganese nickel composite oxide. ₃ Was confirmed.
[0106]
When the tap density of the obtained powder was measured, it was 1.09 g / cm ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.169 °.
[0107]
In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, a shelf in a low potential region around 3.5 to 4 V appeared in a discharge curve. This is presumably because a heterogeneous phase appeared in addition to the spinel-type lithium-manganese-nickel composite oxide and the lattice constant of the cubic unit cell became too small.
[0108]
(Comparative Example 9)
Lithium hydroxide monohydrate (LiOH. (H ₂ O) (manufactured by FMC)) and the manganese nickel composite oxide were mixed, and a manganese nickel composite oxide was prepared in the same manner as in Example 1 except that the sintering temperature was 800 ° C.
[0109]
As a result, the average particle diameter was about 14 μm and the specific surface area was 0.4 m. ² / G of substantially spherical secondary particles were obtained. When the obtained powder was analyzed by powder X-ray diffraction using Cu-Kα radiation, NiO peak was confirmed in addition to the cubic spinel-type lithium manganese nickel composite oxide.
[0110]
When the tap density of the obtained powder was measured, it was 1.57 g / cm. ³ Met. The lattice constant calculated by Rietveld analysis of the X-ray diffraction pattern was 8.186 °.
[0111]
In addition, as a result of performing a charge / discharge test by producing a battery using the obtained active material, a shelf in a low potential region around 3.5 to 4 V appeared in a discharge curve. This is probably because a large amount of heterogeneous phase appeared in addition to the spinel-type lithium manganese nickel composite oxide and the lattice constant of the cubic unit cell became too large.
[0112]
Table 1 shows the production conditions and the physical properties of the obtained lithium manganese nickel composite oxide in each of the examples and comparative examples.
[0113]
[Table 1]

[0114]
As is clear from FIG. 5, in comparison with Example 1, in Comparative Examples 1 to 3, shelves in a low potential region around 3.5 to 4 V appear in the discharge curves. This is considered to be because Comparative Examples 1 to 3 were not single-phase spinel structures as shown in FIGS.
[0115]
On the other hand, in Example, the tap density was 1.5 g / cm. ³ From the above, it is expected that the volume energy density of the battery will increase, and the specific surface area of the example can be reduced as compared with the comparative example. As shown in the discharge curve of Example 1 in FIG. 5, while maintaining the effect of preventing the characteristic deterioration of the above, a region exceeding 4.5 V is 120 mAh / g or more and a low region around 3.5 to 4 V is obtained. It can be said that the superiority in comparison with the related art that the shelf in the potential region does not appear is shown.
[0116]
【The invention's effect】
The spinel-type lithium composite oxide obtained by the present invention has a general formula Li _{(1 + X)} Mn _(2-YX) Ni _Y O ₄ (Where X and Y are -0.05 ≦ X ≦ 0.10 and 0.45 ≦ Y ≦ 0.55, respectively) In the method for producing a lithium manganese nickel composite oxide having a spinel structure represented by: , A manganese salt and a nickel salt are charged into a solvent so that the manganese and nickel have the atomic ratio of manganese and nickel in the above general formula. A first step of obtaining a mixture of a salt and a nickel salt, a second step of firing the mixture at 800 to 1000 ° C. to obtain a composite oxide of manganese and nickel, and a composite oxide and lithium obtained in the second step. A third step of calcining the compound at 600 to 750 ° C., wherein the mixture is adjusted so that the ratio of the total number of moles of manganese and nickel to the number of moles of lithium is substantially 2: 0.95 to 1.10. Made with The method is a complex oxide obtained using a spinel-type crystal structure single phase, with no crystal defect lithium-manganese-nickel composite oxide is obtained. Thus, while maintaining a high tap density, the discharge curve does not show a shelf in a low potential region near 3.5 to 4 V, and has excellent potential flatness in a high potential region. This has the effect of realizing a non-aqueous electrolyte secondary battery having a large capacity and a high energy density.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction diagram of a dry powder of a lithium nickel manganese composite oxide obtained by a method of Example 1 of the present invention.
FIG. 2 is an X-ray diffraction diagram of a dry powder of a lithium nickel manganese composite oxide obtained by the method of Comparative Example 1.
FIG. 3 is an X-ray diffraction diagram of a dry powder of a lithium nickel manganese composite oxide obtained by the method of Comparative Example 2.
4 is an X-ray diffraction diagram of a dry powder of a lithium nickel manganese composite oxide obtained by the method of Comparative Example 3. FIG.
FIG. 5 is a diagram showing the results of a charge / discharge test in Examples and Comparative Examples 1 to 3.
FIG. 6 is a diagram showing the structure of a coin battery used for performing a charge / discharge test.
FIGS. 7A and 7B are SEMs of a manganese nickel composite oxide (a) spray-dried and fired by the spray dryer of Example 1 and a spinel-type lithium manganese nickel composite oxide (b) synthesized. It is a photographic image, (c)-(e) is a SEM photographic image of the lithium manganese nickel composite oxide of each of Comparative Examples 1-3 in order.
[Explanation of symbols]
1 Lithium metal negative electrode
2 Separator (impregnated with electrolyte)
3 Positive electrode (Evaluation electrode)
4 Gasket
5 Negative electrode can
6 Positive electrode can
7 Current collector

Claims (6)

General formula: Li _{(1 + X)} Mn _(2-YX) Ni _Y O ₄ (where X and Y in the formula are -0.05 ≦ X ≦ 0.10 and 0.45 ≦ Y ≦ 0.55, respectively) are lithium manganese nickel composite oxides having a spinel structure. The cubic unit cell has a lattice constant of 8.17 to 8.18 °, a specific surface area of 0.2 to 1.0 m ² / g, a tap density of 1.52 g / cm ³ or more, and a discharge curve of 4 A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein a region exceeding 0.5 V is 120 mAh / g or more, and a shelf in a potential region is excluded from 3.5 to 4.5 V. General formula: Li _{(1 + X)} Mn _(2-YX) Ni _Y Production of lithium manganese nickel composite oxide having a spinel structure represented by O ₄ (where X and Y are -0.05 ≦ X ≦ 0.10 and 0.45 ≦ Y ≦ 0.55, respectively) In the method,
A manganese salt and a nickel salt are charged into a solvent so as to have an atomic ratio of manganese and nickel represented by the above general formula, pulverized and mixed until the average particle size becomes 0.1 μm or less, and the obtained slurry is spray-dried. A first step of obtaining a mixture of a manganese salt and a nickel salt;
A second step of firing the mixture at 800 to 1000 ° C. to obtain a composite oxide of manganese and nickel;
The resulting composite oxide and lithium compound were adjusted such that the ratio of the total number of moles of manganese and nickel to the number of moles of lithium was substantially 2: 0.95-1.10, and the resulting mixture was obtained. A third step of firing at 600 to 750 ° C.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising: The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein the firing temperature of the mixture of the manganese salt and the nickel salt is 800 ° C or more and less than 900 ° C. 3. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein at least one selected from manganese carbonate, manganese carbonate hydrate, manganese hydroxide, and manganese oxyhydroxide is used as the manganese salt. . The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein at least one selected from nickel carbonate, nickel carbonate hydrate, nickel hydroxide, and nickel oxyhydroxide is used as the nickel salt. . The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein a wet pulverizer is used for pulverizing and mixing the manganese salt and the nickel salt.

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