JP3982658B2 - Positive electrode active material for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery using the positive electrode active material - Google Patents

Description

【００８３】
表１に示すように、実施例１〜６は、比較例１〜７に比べて、放電容量が大きく、高容量であり、かつ５００サイクル目の容量保持率が大きく、サイクル特性が優れていた。上記のように、実施例１〜６の放電容量が大きいことなどからもわかるように、実施例１〜６で用いたスピネル型リチウムマンガン酸化物は球状ないし楕円状の粒子であるため、正極の作製にあたっての充填性も良好であったと考えられる。また、実施例１〜６は放電容量が大きく、かつ負荷特性が優れていた。これは、実施例１〜６では、Ｆｅ含有量が２００ｐｐｍ以下のスピネル型リチウムマンガン酸化物を正極活物質として用いたことによるものと考えられる。さらに、実施例１〜６は低温時の放電特性も優れていた。これは、実施例１〜６では、平均粒子径が１〜４５μｍの範囲内にあり、かつ比表面積が０．５〜３ｍ² ／ｇの範囲内にあるスピネル型リチウムマンガン酸化物を正極活物質として用いたことによるものと考えられる。
【００８４】
これに対して、組成が一般式Ｌｉ_x Ｍｎ_y Ｏ_4-z （ｘ＋ｙ＝３．００とした時、１．００≦ｘ≦１．０５、０＜ｚ≦０．１５、ただし、ｘは電池組立時の値であり、充放電に際し０＜ｘ≦１．０５の範囲で変化する値である）の範囲から外れるリチウムマンガン酸化物を正極活物質として用いた比較例１〜７は、実施例１〜６に比べて、放電容量が小さく、サイクル特性が悪かった。また、比較例２〜７のように、本発明の製造条件から外れた場合は、本発明のような放電容量が大きく、かつサイクル特性が優れたリチウムマンガン酸化物を製造することができなかった。また、Ｆｅ含有量が２００ｐｐｍより多いスピネル型リチウムマンガン酸化物を正極活物質として用いた比較例２〜４では負荷特性が悪く、特に比較例５や比較例６ではスピネル構造のみのリチウムマンガン酸化物を得ることができなかった。さらに、比較例１〜７は、平均粒子径が１〜４５μｍの範囲外で、比表面積も０．５〜３ｍ² ／ｇの範囲外にあるため、低温時の放電特性が悪かった。
【００８５】
【発明の効果】
以上説明したように、本発明では、一般式Ｌｉ_x Ｍｎ_y Ｏ_4-z （ｘ＋ｙ＝３．００とした時、１．００≦ｘ≦１．０５、０＜ｚ≦０．１５、ただし、ｘは電池組立時の値であり、充放電に際し０＜ｘ≦１．０５の範囲で変化する値である）で表される球状ないし楕円状のスピネル型リチウムマンガン酸化物で正極活物質を構成することにより、資源的に豊富で安価なマンガンを構成元素として用い、非水電解液二次電池に高容量と優れたサイクル特性を付与することができる非水電解液二次電池用正極活物質を提供することができた。また、本発明では、上記スピネル型リチウムマンガン酸化物中のＦｅ含有量を２００ｐｐｍ以下にし、そのＦｅ含有量を２００ｐｐｍ以下にしたスピネル型リチウムマンガン酸化物を正極活物質として用いることにより、放電容量が大きく、かつ、負荷特性が優れた非水電解液二次電池を提供することができた。さらに、本発明では、上記スピネル型リチウムマンガン酸化物の平均粒子径を１〜４５μｍの範囲内にし、比表面積を０．５〜３ｍ² ／ｇの範囲内にして正極活物質として用いることにより、低温時の放電特性が優れた非水電解液二次電池を提供することができた。
【００８６】
また、本発明のスピネル型リチウムマンガン酸化物は、球状ないし楕円状の粒子であるから、正極の作製にあたって充填性が良く、また、資源的に豊富で安価なマンガンを構成元素としているので、大量生産にも適しており、その産業上の意義が大きい。
【図面の簡単な説明】
【図１】本発明のスピネル型リチウムマンガン酸化物の粒子構造を示す倍率１５１０倍の電子顕微鏡写真である。
【図２】市販のＬｉＭｎ₂ Ｏ₄ の粒子構造を示す倍率１５００倍の電子顕微鏡写真である。
【図３】非水電解液二次電池の一例を模式的に示す部分断面斜視図である。
【符号の説明】
１ 正極
２ 負極
３ セパレータ
４ 電池ケース
５ 絶縁体
６ 絶縁体
７ 絶縁パッキング
８ 封口体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery using the positive electrode active material. More specifically, the present invention relates to a high capacity and excellent cycle characteristics. Non-aqueous electrolyte for non-aqueous electrolyte secondary battery capable of providing a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte having high capacity and excellent cycle characteristics using the positive electrode active material The present invention relates to a secondary battery.
[0002]
[Prior art]
In recent years, with the development of portable electronic devices such as mobile phones and laptop computers, and the practical application of electric vehicles, secondary batteries with small size and light weight and high capacity have been required. Currently, as a high-capacity secondary battery that meets this requirement, LiCoO as a positive electrode active material₂Lithium ion secondary batteries using a carbon-based material as a negative electrode active material have been commercialized. LiCoO used as the positive electrode active material of this lithium ion secondary battery₂Is widely used as a preferred positive electrode active material because it is easy to manufacture and easy to handle.
[0003]
However, LiCoO₂Is manufactured using cobalt (Co), a rare metal, as a raw material, and it is expected that resource shortages will become serious in the future. Further, since the price of cobalt itself is high and the price fluctuates greatly, development of a positive electrode material that is inexpensive and stable in supply is desired.
[0004]
Therefore, LiCoO₂Research has been conducted on lithium ion secondary batteries using spinel-structured lithium manganese oxide, nickel nickelate, lithium titanate, or the like as a positive electrode active material that can be used as an alternative. Among these lithium-containing composite oxides, lithium manganese oxide having a spinel structure with manganese as a constituent element, whose constituent elements are inexpensive and stable in supply, is LiCoO.₂As a positive electrode active material that can replace
[0005]
This spinel-type lithium manganese oxide includes Li₂Mn_FourO₉, Li_FourMn_FiveO₁₂, LiMn₂O_FourAmong them, especially LiMn₂O_FourHas been actively researched (Japanese Patent Laid-Open No. 6-76824, Japanese Patent Laid-Open No. 7-73883, and Japanese Patent Laid-Open No. 7-230802). JP, 7-245106, A, etc.).
[0006]
[Problems to be solved by the invention]
By the way, LiCoO₂The theoretical discharge capacity of 274 mAh / g is LiCoO when deep charge / discharge is performed.₂Causes a phase change and affects the cycle life, so that a practical discharge capacity in an actual lithium ion secondary battery is in the range of 125 to 140 mAh / g. In contrast, LiMn₂O_FourThe theoretical discharge capacity is 148 mAh / g.₂O_FourLiCoO₂In the same way as in the case of using a carbon-based material as a negative electrode active material during a charge / discharge, and because the irreversible capacity of the carbon-based material is large, the discharge capacity that can be used when actually making a battery Is about 90 to 105 mAh / g. As is clear from this, LiMn₂O_FourWhen Li is used as the positive electrode active material, LiCoO₂The battery capacity cannot be increased as compared with the case where is used as the positive electrode active material.
[0007]
LiCoO₂The true density of 4.9-5.1 g / cm^ThreeWhereas LiMn₂O_FourThe true density of is 4.0-4.2 g / cm^ThreeIn view of the filling property as the positive electrode active material, there is a disadvantage in terms of capacity. In addition, LiMn₂O_FourIn a lithium ion secondary battery using as a positive electrode active material, LiMn during charging and discharging₂O_FourSince its structure is unstable, the cycle characteristics are LiCoO₂There is also a problem that it is shorter than the battery.
[0008]
Furthermore, since a non-aqueous electrolyte using an organic solvent is used as the electrolyte solvent in the lithium ion secondary battery, the conductivity of ions in the electrolyte is low, so that a large current is taken out from the battery. When a heavy load is applied, the decrease in discharge voltage is greater than during low-load discharge, resulting in a problem that the battery capacity cannot be taken out sufficiently, and because the polarization of the positive electrode active material is large, the environmental temperature during battery use is low. However, there is a problem that the discharge voltage is greatly lowered compared with the discharge characteristics at room temperature, and the battery capacity is remarkably difficult to take out.
[0009]
In light of the above-described conventional circumstances, a first object of the present invention is to provide a positive electrode active material for a nonaqueous electrolyte secondary battery that is structurally stable and has a high capacity. A second object of the present invention is to provide a non-aqueous electrolyte secondary battery that uses the positive electrode active material and has a high capacity and excellent cycle characteristics. Furthermore, the present invention is a non-aqueous electrolyte secondary battery that improves the utilization rate of the positive electrode active material, has excellent load characteristics, and has excellent discharge characteristics at low temperatures, according to the recent usage environment of secondary batteries. The third purpose is to provide
[0010]
[Means for Solving the Problems]
  As a result of intensive studies to solve the above-mentioned problems, the present inventors have been produced using chemically synthesized manganese dioxide having a Fe content of 98 ppm or less as a manganese source as a positive electrode active material for a non-aqueous electrolyte secondary battery. , General formula Li_xMn_yO_4-z(When x + y = 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦ 0.15, where x is a value when assembling the battery, and 0 <x ≦ 1.05 during charging and discharging. When a spinel type lithium manganese oxide having a spherical or elliptical shape and an Fe content of 200 ppm or less is used, it has a discharge capacity closer to the theoretical discharge capacity and a high capacity. It was also found that a non-aqueous electrolyte secondary battery having excellent cycle characteristics and excellent load characteristics can be obtained. Further, the present inventors also have the general formula Li_xM_yO_4-zThe mixing ratio of chemically synthesized manganese dioxide having a Fe content of 98 ppm or less and a lithium salt is set to Li / Mn ≦ 0.50 in terms of the molar ratio of Li and Mn. It has also been found that it can be produced by firing at 780 to 820 ° C. while supplying a mixed gas with oxygen gas at a flow rate of 1 liter / min or more per 100 g of the raw material mixture. Furthermore, the present inventors set the specific surface area of the spinel type lithium manganese oxide to 0.5 to 3 m.²It has also been found that a non-aqueous electrolyte secondary battery having excellent discharge characteristics at low temperatures can be obtained by setting the average particle size to 1 to 45 μm within the range of / g.
[0011]
Hereinafter, the present invention will be described more specifically. First, the characteristics of the spinel type lithium manganese oxide as a positive electrode active material for a non-aqueous electrolyte secondary battery will be described. In the spinel type lithium manganese oxide, the content ratio of its constituent elements Li, Mn, O However, it greatly affects the electrochemical capacity.
[0012]
Conventional LiMn₂O_FourAs is clear from the composition ratio, the average valence of Mn is 3.5, and usually, an equal amount of trivalent Mn and tetravalent Mn are mixed. However, only trivalent Mn is actually involved in charging and discharging, and LiMn₂O_FourIt has been clarified that the discharge capacity increases as the amount of trivalent Mn in the composition increases. Therefore, in order to increase trivalent Mn, LiMn₂O_FourIt is conceivable to use lithium manganese oxide with a reduced amount of oxygen in the crystal structure.
[0013]
However, when the amount of trivalent Mn increases, LiMn₂O_FourFrom cubic spinel structure to tetragonal LiMnO₂A phase change occurs. This tetragonal LiMnO₂Can be charged and discharged in the 3V region at a lithium potential, but cannot be used when a high potential in the vicinity of 4V is required. LiMn₂O_FourThe oxygen content in LiMn₂O_FourIt is important to determine the valence of Mn therein, and when the oxygen content is high, tetravalent Mn increases, and when the oxygen content is low, trivalent Mn increases. Because trivalent Mn is a yarn-teller effect, the material itself is likely to undergo phase change when valence changes, and LiMn during charge / discharge₂O_FourThis structure is unstable, and the spinel phase is likely to be destroyed as Li ions enter and exit.
[0014]
LiMn₂O_FourThe amount of Li changes in the range of 0 to 1.00 by doping and dedoping Li in the crystal structure, and electrochemical charging / discharging is possible, but if the amount of Li in the crystal structure is small Since the amount of Li that can be used for charging and discharging decreases, the electrochemical capacity decreases. Therefore, it is desirable that the Li content is as high as possible, but excess Li exceeding the stoichiometric composition is LiMn.₂O_FourIn this case, the lithium enters the 16d site where Mn should occupy, and Li which enters the 16d site of Mn does not participate in charge / discharge. Furthermore, when Li enters the 16d site of Mn, LiMn₂O_FourThe tetravalent Mn therein increases and the charge / discharge capacity decreases. Accordingly, when the lithium manganese oxide is expressed as x = y = 3.00 and x + y = 3.00, the Li content is preferably 1.00 but the oxygen content is O._4-zWhen (0 <z ≦ 0.15), a large amount of trivalent Mn can be contained even when the amount of Li is 1.00 or more. On the other hand, if the amount of Li becomes too large, a large amount of impurity phase is generated, so the amount of Li is preferably 1.00 or more and 1.05 or less, and more preferably 1.01 or more and 1.03 or less.
[0015]
In the general formula, O_4-ZWhen the oxygen content indicated by is too large, tetravalent Mn increases as described above, and the charge / discharge capacity decreases, so the oxygen content is preferably less than 4 and 3.85 or more, 3.98 or less and 3.88 or more are more preferable.
[0016]
The spinel-type lithium manganese oxide of the present invention undergoes charge / discharge cycles when Li (lithium) in the crystal structure is doped / undoped, and the composition during battery assembly and charge / discharge cycles is as follows. become that way.
Composition during battery assembly
Li_xMn_yO_4-z
(X + y = 3.00, 1.00 <x ≦ 1.05, 0 <z ≦ 0.15)
Charging / discharging composition
Li_{x '}Mn_yO_4-z
(0 <x ′ ≦ 1.05, 1.95 / 4.00 <y / (4-z) ≦ 2.00 / 3.85)
At the time of charging / discharging, the amount of lithium changes in the range of 0 <x ′ ≦ 1.05, and the ratio of manganese to oxygen amount is 1.95 / 4.00 <y / (4-z) ≦ 2.00 / It will be within the range of 3.85.
[0017]
Based on the above knowledge, the present invention, with respect to lithium manganese oxide, maintains as much spinel structure as possible, contains as much trivalent Mn as possible, increases discharge capacity, and fully supports 4V class high potential. It is something that can be done. That is, the present invention relates to the general formula Li_xMn_yO_4-z(When x + y = 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦ 0.15, where x is a value when assembling the battery, and 0 <x ≦ 1.05 during charging and discharging. The spinel type lithium manganese oxide of the present invention is a conventional positive electrode active material for a non-aqueous electrolyte secondary battery composed of a spinel type lithium manganese oxide. Compared to lithium manganese oxide, the oxygen content in the crystal structure is suppressed, and even when a large amount of trivalent Mn is contained, the cycle life is long and the cycle characteristics are excellent.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The spinel type lithium manganese oxide of the present invention has the general formula Li as described above._xMn_yO_4-z(When x + y = 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦ 0.15, where x is a value when assembling the battery, and 0 <x ≦ 1.05 during charging and discharging. In the detailed description of the spinel type lithium manganese oxide, the conventional LiMn₂O_FourAs for the shape and production raw materials, LiMn₂O_FourIn general, electrolytically synthesized manganese dioxide is used as a production raw material. However, LiMn produced using this conventional electrolytically synthesized manganese dioxide₂O_Four2 has an angular shape as shown in the electron micrograph of FIG. 2 (in FIG. 2, the portion that appears whitish is LiMn).₂O_FourParticles).
[0019]
In a non-aqueous electrolyte secondary battery, it is necessary to increase the density of the positive electrode mixture to increase the capacity, but the LiMn has the angular shape as described above.₂O_FourThen, because of the angular shape, there is a problem that the mixture density cannot be increased and the filling density is lowered.
[0020]
The spinel type lithium manganese oxide of the present invention can meet such demands, and as shown in FIG. 1 (the portion shown in whitish in FIG. 1 is the spinel type lithium manganese oxide of the present invention). It is considered that the electrochemical reaction in the active material particles proceeds uniformly, and thus a large discharge capacity can be expected. When spinel type lithium manganese oxide is used as the positive electrode active material, the packing density of the positive electrode mixture can be increased, and a high capacity non-aqueous electrolyte secondary battery can be obtained. In the present invention, when expressing the shape of the spinel type lithium manganese oxide, it is expressed as spherical or elliptical, but this is all from a spherical shape to a substantially elliptical shape (that is, from a substantially spherical shape). It is meant that any shape included therein may also be included.
[0021]
As will be described in detail later, the spinel type lithium manganese oxide of the present invention preferably has an average particle size of 1 to 45 μm, and particularly an average particle size of 1 to 25 μm, in order to increase charge / discharge efficiency. preferable. In addition, the specific surface area is 0.5 to 3 m in order to increase the effective reaction area.²/ G is preferred, especially 1 to 3 m²/ G is preferred.
[0022]
In addition, when the spinel type lithium manganese oxide is used as the positive electrode active material by setting the Fe content in the spinel type lithium manganese oxide to 200 ppm or less, the present inventors have the charge / discharge capacity and cycle. It has been found that the load characteristics can be improved as well as the characteristics.
[0023]
That is, transition metals other than manganese are mixed in the process of producing chemically synthesized manganese dioxide, which is a raw material of the lithium manganese oxide of the present invention. It has been found that when lithium manganese oxide is synthesized using manganese dioxide as a raw material, the charge / discharge capacity of the product can be further improved, and a nonaqueous electrolyte secondary battery with excellent load characteristics can be obtained. The reason for this is not necessarily clear at present, but the present inventors have considered that when manganese dioxide containing Fe is used, iron oxide or Fe that does not contribute to the charge / discharge reaction in the formation process of lithium manganese oxide is used. It is considered that the contained lithium oxide is generated, which causes the load characteristics to deteriorate. Therefore, by using manganese dioxide with a low Fe content, the generation of those impurities is suppressed, and the Fe content in the lithium manganese oxide is reduced to 200 ppm or less, so that doping and dedoping are performed in the charge / discharge reaction. It is considered that the efficiency of lithium ion diffusion in the solid phase can be improved, and not only the charge / discharge capacity can be improved, but also the load characteristics can be improved.
[0024]
Moreover, in order to synthesize one equivalent of the product lithium manganese oxide, two equivalents of manganese dioxide as a raw material are required, so the Fe component which is an impurity in manganese dioxide is about twice that in lithium manganese oxide. Therefore, it is considered that the Fe component concentration in manganese dioxide is very likely to affect the load characteristics of the spinel type lithium manganese oxide.
[0025]
According to the study by the present inventors, the lithium manganese oxide is used as a positive electrode active material by setting the Fe content in the lithium manganese oxide to 200 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less. It was found that a non-aqueous electrolyte secondary battery having a high charge / discharge capacity and excellent load characteristics can be obtained.
[0026]
In addition, the present inventors have preferred that the particle size of the spinel-type lithium manganese oxide is 1 to 45 μm as the average particle size, and particularly preferably 1 to 25 μm as the average particle size in order to increase charge / discharge efficiency. The specific surface area is 0.5 to 3 m in order to increase the effective reaction area.²/ G is preferred, especially 1 to 3 m²/ G is preferred, the general formula Li of the present invention_xMn_yO_4-zBy making the spherical or elliptical spinel-type lithium manganese oxide represented by the above average particle diameter and specific surface area, the progress of the electrochemical reaction becomes advantageous, and not only the charge / discharge capacity and cycle characteristics It was found that the discharge characteristics at low temperature can also be improved.
[0027]
The average particle size of the spinel type lithium manganese oxide of the present invention is 1 to 45 μm, and the specific surface area is 0.5 to 3 m.²The reason why not only the excellent charge / discharge capacity and cycle characteristics but also the discharge characteristics at a low temperature can be improved by setting to / g is not necessarily clear at present, but is considered as follows. That is, the positive electrode of the non-aqueous electrolyte secondary battery of the present invention is a paste in which the spinel type lithium manganese oxide is dispersed in a solvent together with a binder, and this is applied onto a substrate serving as a current collector and dried. The average particle diameter of the spinel type lithium manganese oxide is 1 μm or more and the specific surface area is 3 m.²/ G or less can suppress aggregation of the spinel-type lithium manganese oxide particles in the positive electrode mixture paste and improve the wettability of the spinel-type lithium manganese oxide particles to the solvent. The amount of solvent used can be reduced. Although the solvent remaining in the active material-containing layer (that is, the positive electrode mixture layer) after drying the paste affects the load characteristics, the spinel type lithium manganese oxide of the present invention reduces the amount of solvent used as described above. Therefore, it is possible to reduce the residual solvent in the positive electrode mixture, and to lower the drying temperature of the paste applied on the substrate, which contributes to the battery characteristics during the positive electrode manufacturing process. The distribution of spinel-type lithium manganese oxide, binder, and electron conduction aid in the positive electrode mixture after drying the paste becomes uniform, improving the load characteristics, thereby improving not only the charge / discharge capacity and cycle characteristics but also at low temperatures. It is considered that the discharge characteristics of the battery will be improved.
[0028]
On the other hand, the average particle size of spinel type lithium manganese oxide is 45 μm or less and the specific surface area is 0.5 m.²/ G or more facilitates the progress of the electrochemical reaction on the surface of the spinel-type lithium manganese oxide particles, and the fine lithium manganese oxide can be obtained. The density can be further increased, and the effect of the spherical or elliptical particle shape of the present invention can be expressed more remarkably. The average particle diameter referred to in the present invention is an electron micrograph (magnification: 500 times), which is a value obtained by measuring the particle diameter of individual particles in the photograph and calculating the average value of the particle diameters of 50 particles. The specific surface area means that 1 g of a sample is deaerated at 120 ° C. for 20 hours, and the nitrogen adsorption method (manufactured by Yuasa Ionix Co., Ltd.) is applied to pores of 1 to 100 mm after the measurement environment vacuum degree is 10 mTorr or less The value obtained from the measurement with the adsorbent at the time of measurement with the autosorb 1).
[0029]
Next, the method for producing the spinel type lithium manganese oxide of the present invention will be described. As the manganese source, chemically synthesized manganese dioxide is used, and in this case, it is preferable to use a spherical or elliptical one. By using this spherical or elliptical chemically synthesized manganese dioxide, the obtained spinel type lithium manganese oxide can be made spherical or elliptical. In order to produce the spinel type lithium manganese oxide having the above average particle size and specific surface area, the particle size of manganese dioxide is preferably 1 to 45 μm in terms of average particle size, and more preferably 1 to 25 μm in terms of average particle size. In addition, in order to make the Fe content in the obtained spinel type lithium manganese oxide 200 ppm or less, chemically synthesized manganese dioxide having a low Fe content is used, and the temperature is within the range of the production conditions of the present invention described later. It is preferable to appropriately select the atmosphere, gas flow rate, and the like.
[0030]
Chemically synthesized manganese dioxide having a low Fe content as described above is used in the process of producing manganese dioxide, from the stage where manganese is dissolved as an ion in an aqueous solution, and then the Fe component is salted by addition of calcium carbonate or sulfurization. Can be produced by adjusting the pH in the solution and the amount added. Also, in the process of precipitating manganese ions with ammonium carbonate or the like and taking it out as manganese carbonate, the Fe component simultaneously precipitates when the pH or addition amount in the solution is not sufficiently adjusted in the above-described process. Although there is a possibility, manganese dioxide with a low Fe content can be produced by adjusting the addition amount of ammonium carbonate or the like and the pH in the solution.
[0031]
As the lithium source, various lithium salts can be used. For example, lithium hydroxide monohydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, lithium fluoride, iodine Lithium fluoride, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide, etc. are mentioned. Among them, gases that adversely affect the environment such as carbon oxide, nitrogen oxide, sulfur oxide are generated Lithium hydroxide monohydrate is preferable in that it does not.
[0032]
In the production of the spinel type lithium manganese oxide of the present invention, the charge ratio of manganese dioxide and lithium salt is Li / Mn ≦ 0.5, especially 0.45 ≦ Li / Mn ≦ 0, as a mixed molar ratio of Li and Mn. .49 is preferred. It is preferable to set the mixed molar ratio of Li and Mn to 0.5 or less. When the mixed molar ratio of Li / Mn is larger than 0.5, reaction intermediate products and the like are likely to remain, This is because the intermediate product may inhibit the charge / discharge reaction in the battery system and reduce the charge / discharge capacity of the non-aqueous electrolyte secondary battery.
[0033]
Moreover, at the time of manufacturing the spinel type lithium manganese oxide of the present invention, it is preferable that the above manganese dioxide and lithium salt are mixed and pelletized to be fired. That is, since the reaction is carried out by solid phase reaction, the reaction proceeds by diffusion in the solid phase of the raw material. By pelletizing, the contact between the lithium salt particles of the raw material and the manganese dioxide particles is improved, and the reaction is further improved. Becomes easier to progress. The size of the pellet is preferably 5 to 15 mm.
[0034]
And baking at the time of manufacture of the spinel type lithium manganese oxide of this invention heats up to 780-820 degreeC, and it is preferable to hold | maintain at that temperature for 24 to 36 hours. By baking at 780-820 degreeC, the crystallinity of the lithium manganese oxide to produce | generate improves and it becomes easy to form a spinel type manganese structure. When the firing temperature is lower than 780 ° C., the discharge capacity is reduced due to the decrease in crystallinity of the product spinel-type lithium manganese oxide and the generation of impurities, and when the firing temperature is higher than 820 ° C., the spinel-type lithium manganese oxide Since the difference between the charge capacity and the discharge capacity, that is, the irreversible capacity increases, the discharge capacity decreases.
[0035]
As the heat treatment for the firing, it is preferable to raise the temperature to 780 to 820 ° C. after preheating from 250 to 500 ° C. which is the melting point of the lithium salt from room temperature, rather than raising the temperature to 780 to 820 ° C. all at once. . This is because the reaction between the lithium salt and manganese dioxide occurs in stages, and spinel-type lithium manganese oxide is formed via the intermediate product, so that the first stage for forming each intermediate product. This is for preheating as a reaction. When the temperature is raised to 780-820 ° C. at once, the lithium salt and manganese dioxide partially react to the final stage, and the spinel type lithium manganese oxide generated thereby is unreacted. May interfere with the reaction of things. In order to shorten the firing time for obtaining the intended spinel type lithium manganese oxide, it is effective to perform heating stepwise. The preheating time is not particularly limited, but usually 12 to 30 hours are preferable, and it is preferable that the temperature is raised from room temperature to near the melting point of the lithium salt and further heated while maintaining the temperature.
[0036]
The atmosphere for the heat treatment including the firing and preheating is preferably performed in a mixed atmosphere of an inert gas such as argon, helium, and nitrogen and oxygen gas. The mixing ratio of these gases is preferably in the range of 5/5 to 9/1, more preferably in the range of 8/2 to 9/1, by the volume ratio of inert gas / oxygen gas. As described above, by setting the inert gas / oxygen gas to a volume ratio of 5/5 to 9/1, the progress of the reaction is facilitated, and the spinel-type lithium manganese oxide containing no impurities can be easily obtained. It becomes like this.
[0037]
The flow rate of the mixed gas of the inert gas and oxygen gas is preferably 1 liter / min or more per 100 g of the starting raw material mixture, and more preferably 1 to 5 liter / min per 100 g of the raw material mixture. When the gas flow rate is small, that is, when the gas flow rate is slow, the reactivity to the spinel structure is different, and Mn₂O_ThreeOr Li₂MnO_ThreeSuch impurities may remain.
[0038]
In order to produce a positive electrode for a non-aqueous electrolyte secondary battery using the spinel type lithium manganese oxide of the present invention as the positive electrode active material, for example, the lithium manganese oxide, for example, flake graphite In addition, an electron conduction assistant such as acetylene black and a binder such as polytetrafluoroethylene and polyvinylidene fluoride may be added and mixed, and the resulting positive electrode mixture may be formed by an appropriate means.
[0039]
As an active material of the negative electrode facing the positive electrode, lithium or a lithium-containing compound is used, and examples of the lithium-containing compound include lithium alloys and other compounds. Examples of the lithium alloy include lithium-aluminum, lithium-lead, lithium-indium, lithium-gallium, and lithium-indium-gallium. Examples of lithium-containing compounds other than lithium alloys include tin oxide, silicon oxide, nickel-silicon alloys, magnesium-silicon alloys, carbon materials having a disordered layer structure, graphite, tungsten oxide, and lithium iron composite oxide. Such as things. Some of these exemplary lithium-containing compounds do not contain lithium at the time of production, but when they act as a negative electrode active material, they are in a state containing lithium. Of these, graphite is particularly preferable because of its large capacity density.
[0040]
The negative electrode is mixed with the negative electrode active material, if necessary, by adding the same binder or electron conduction aid as in the case of the positive electrode active material, and molding the obtained negative electrode mixture by an appropriate means. Produced.
[0041]
The positive electrode and negative electrode forming means include pressure forming a positive electrode mixture and a negative electrode mixture, or forming a positive electrode mixture and a negative electrode mixture into a paste or slurry with water or other appropriate solvent. Various means can be employed such as coating or impregnating the coating material on the substrate that also serves as a current collector and drying to form a coating film on the substrate. However, when forming the coating film on the latter substrate Is suitable.
[0042]
As an application method for applying the paint to the substrate, various application methods such as an extrusion coater, a reverse roller, a doctor blade, and the like can be employed. In addition, as a substrate for electrodes such as a positive electrode and a negative electrode, for example, a metal net such as aluminum, stainless steel, titanium, copper, punched metal, expanded metal, foam metal, foil, or the like is used.
[0043]
The ratio of the amount of active material between the positive electrode and the negative electrode varies depending on the type of the negative electrode active material, but is preferably positive electrode active material / negative electrode active material = 1.5 to 3.5 (weight ratio).
[0044]
In the non-aqueous electrolyte secondary battery using the spinel type lithium manganese oxide of the present invention as the positive electrode active material, an organic solvent-based non-aqueous electrolyte solution in which an electrolyte is dissolved in an organic solvent is used as the electrolyte solution. The solvent of the electrolytic solution is not particularly limited, but it is particularly suitable to use a chain ester as the main solvent. Examples of such chain esters include chain COO-bonds such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl acetate (EA), and methyl propionate (MP). An organic solvent having The fact that this chain ester is the main solvent of the electrolytic solution means that these chain esters occupy a volume of more than 50% by volume in the total electrolyte solvent, and in particular, the chain ester is the total solvent. It is preferable that 65% by volume or more in the electrolyte solvent, especially the chain ester occupies 70% by volume or more in the entire electrolyte solvent, and in particular, the chain ester occupies 75% by volume or more in the total electrolyte solvent. Is preferred.
[0045]
As the solvent of the electrolytic solution, it is preferable to use this chain ester as the main solvent because the battery ester, particularly the low-temperature characteristics, is improved when the chain ester exceeds 50% by volume in the total electrolyte solvent. This is because that.
[0046]
However, as the electrolyte solvent, in order to improve battery capacity rather than using only the above-mentioned chain ester, an ester having a high induction rate (ester having an induction rate of 30 or more) is mixed with the chain ester. It is preferable to use it. The amount of such an ester having a high dielectric constant in the total electrolyte solvent is preferably 10% by volume or more, particularly preferably 20% by volume or more. That is, when the ester having a high dielectric constant becomes 10% by volume or more in the total electrolyte solvent, the capacity is clearly improved, and when the ester having a high dielectric constant becomes 20% by volume or more in the total electrolyte solvent. The increase in capacity becomes even clearer. However, if the volume of the ester having a high dielectric constant in the total electrolyte solvent is too large, the discharge characteristics of the battery tend to deteriorate. As mentioned above, it is preferably 10% by volume or more, more preferably 20% by volume or more, preferably 40% by volume or less, more preferably 30% by volume or less, and further preferably 25% by volume or less.
[0047]
Examples of the ester having a high dielectric constant include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (γ-BL), ethylene glycol sulfite (EGS), and the like. In particular, cyclic structures such as ethylene carbonate and propylene carbonate are preferred, cyclic carbonates are particularly preferred, and ethylene carbonate (EC) is most preferred.
[0048]
Examples of the solvent that can be used in combination with the ester having a high dielectric constant include 1,2-dimethoxyethane (1,2-DME), 1,3-dioxolane (1,3-DO), and tetrahydrofuran (THF). , 2-methyl-tetrahydrofuran (2-Me-THF), diethyl ether (DEE) and the like. In addition, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can also be used.
[0049]
As an electrolyte of the electrolytic solution, for example, LiClO_Four, LiPF₆, LiBF_Four, LiAsF₆, LiSbF₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, LiCF_ThreeCO₂, Li₂C₂F_Four(SO_Three)₂, LiN (CF_ThreeSO₂)₂, LiC (CF_ThreeSO₂)_Three, LiCnF_{2n + 1}SO_Three(N ≧ 2) and the like are used alone or in combination of two or more. Especially LiPF₆And LiC_FourF₉SO_ThreeAre preferable because of good charge / discharge characteristics. The concentration of the electrolyte in the electrolytic solution is not particularly limited, but is preferably about 0.3 to 1.7 mol / l, particularly about 0.4 to 1.5 mol / l.
[0050]
As the separator, a separator having sufficient strength and capable of holding a large amount of electrolyte is good. From such a viewpoint, the thickness is 10 to 50 μm, and the porosity is 30 to 70%. A microporous film or a nonwoven fabric made of a copolymer with ethylene is preferable.
[0051]
【Example】
Examples of the present invention will be described below. However, this invention is not limited only to those Examples.
[0052]
Example 1
Chemically synthesized manganese dioxide having a spherical shape (the Fe content in this manganese dioxide is 21 ppm) was previously classified to 45 μm or less. Further, granular lithium hydroxide monohydrate as a lithium source was pulverized by a planetary ball mill until it became a fine powder. Next, 19.23 g of the above chemically synthesized manganese dioxide and 4.36 g of lithium hydroxide monohydrate were mixed, and further sufficiently pulverized and mixed in a planetary ball mill. This mixture was compression-molded into pellets using a press, and the pellets were placed in an alumina boat and fired in a tubular electric furnace. The molar ratio Li / Mn between the amount of Mn in the chemically synthesized manganese dioxide and the amount of Li in lithium hydroxide monohydrate was 0.47.
[0053]
The firing atmosphere is a mixture of argon gas / oxygen gas = 8/2 (volume ratio) as a raw material mixture (that is, a mixture of chemically synthesized manganese dioxide and lithium hydroxide / monohydrate as starting materials) per 100 g. Controlled by supplying at a flow rate of 0.0 l / min. In the firing, the temperature is first raised to 470 ° C. at a temperature rise temperature of 200 ° C./h, maintained at 470 ° C. for 24 hours, preheated, and then heated to 800 ° C. at 100 ° C./h to a temperature of 800 ° C. For 36 hours. Then, it stood to cool naturally, and after the temperature of the baked product became 80 ° C. or lower, the baked product was taken out from the tubular electric furnace and sufficiently pulverized and mixed in a mortar.
[0054]
The fired product was sufficiently pulverized and mixed as described above, and then compression-molded again into a pellet, and the pellet was fired in the same manner as described above. That is, the temperature was increased to 800 ° C. at a temperature increase rate of 200 ° C./h, and the firing was carried out at a temperature of 800 ° C. for 36 hours. Thereafter, the temperature was lowered to room temperature by natural cooling, and after the temperature was lowered, the pellet was sufficiently pulverized in an agate mortar, and the pulverized powder was classified to obtain a spherical or elliptical powder of 45 μm or less. An electron micrograph of the lithium manganese oxide particle structure at a magnification of 1510 is shown in FIG. As shown in FIG. 1, the obtained lithium manganese oxide was spherical or elliptical.
[0055]
Further, when the obtained lithium manganese oxide was analyzed by X-ray diffraction, it was found that the spinel structure LiMn.₂O_FourAs a result of observing a diffraction line peculiar to the above and no peak due to impurities was observed, it was confirmed that the obtained lithium manganese oxide was a lithium manganese oxide having a spinel structure. Furthermore, the composition of Li, Mn, and O of the obtained lithium manganese oxide was measured with an atomic absorption analyzer. The sample was prepared as follows. 10 ml of ion-exchanged water and 10 ml of 12N hydrochloric acid were added to 0.25 g of the produced lithium manganese oxide, and heated until the lithium manganese oxide was completely dissolved. Then, it stood to cool to room temperature, ion-exchange water was added, the whole quantity was made into 100 ml, and the sample for analysis was prepared. Each element was analyzed by the standard addition method. From the analysis results, the composition of the manufactured lithium manganese oxide is Li_1.01Mn_1.99O_3.88It turned out to be. Further, when the Fe content in the lithium manganese oxide was measured by an atomic absorption analyzer in the same manner as the above-described compositional analysis of Li, Mn, and O, the Fe content was 40 ppm.
[0056]
Further, the average particle size of the obtained spinel type lithium manganese oxide was obtained by taking an electron micrograph (magnification: 500 times) of the product, measuring the particle size of individual particles in the photo, and measuring 50 particles. It calculated | required by calculating the average value of a particle diameter. As a result, the average particle size was 25 μm. Furthermore, the specific surface area of the obtained spinel-type lithium manganese oxide was subjected to a degassing treatment at 120 ° C. for 20 hours using an autosorb 1 manufactured by Yuasa Ionics, with a sample pore measurement range of 1 to 100 mm, and measurement of the sample. After confirming that the environmental vacuum was 10 mTorr or less, nitrogen gas was measured as the probe gas, and the specific surface area was 1.0 m.²/ G.
[0057]
A model cell was produced using the spinel type lithium manganese oxide produced by the above method. First, 1.6 g of the above spinel type lithium manganese oxide, 0.3 g of acetylene black, and 0.1 g of polytetrafluoroethylene were weighed and mixed thoroughly in a mortar. The mixture was sufficiently ground on a mortar until it became a gum, and the gum mixture was pressed against a 500 μm mesh sieve to form a powder. 40 mg of this powder was taken and compression-molded with a press machine together with a platinum net having a diameter of 10 mm to produce a pellet-shaped electrode.
[0058]
Using the pellet-shaped electrode produced as described above as a working electrode, using a lithium foil as a counter electrode and a reference electrode, LiPF₆A model cell was prepared by evaluating a positive electrode active material using a non-aqueous solution in which 1.0 mol / l was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 3 at a concentration of 1.0 mol / l. It was.
[0059]
Furthermore, a battery for evaluating cycle characteristics was produced as described below. 250 g of N-methyl-2-pyrrolidone was added to 20 g of polyvinylidene fluoride as a binder and heated to 60 ° C. to dissolve the polyvinylidene fluoride in N-methyl-2-pyrrolidone to prepare a binder solution. 450 g of the above lithium manganese oxide as a positive electrode active material was added to this binder solution, and 5 g of carbon black and 25 g of graphite were added as an electron conduction aid, and stirred to prepare a slurry-like paint.
[0060]
This paint was uniformly applied on both sides of an aluminum foil having a thickness of 20 μm, dried, compression-molded by a roller press machine, and then cut to produce a strip-shaped positive electrode having an average thickness of 190 μm and 483 mm × 54 mm.
[0061]
Also, a binder solution similar to the above was prepared, and 180 g of graphite was added as a negative electrode active material to the binder solution and stirred to prepare a slurry paint. This paint was uniformly applied to both sides of a 18 μm thick copper foil, dried, compression-molded by a roller press, and then cut to produce a strip-like negative electrode having an average thickness of 140 μm and a size of 522 mm × 56 mm.
[0062]
Next, a separator made of a microporous polyethylene film having a thickness of 25 μm is disposed between the belt-like positive electrode and the belt-like negative electrode, wound into a spiral shape to form a spiral electrode body, and then has a bottom with an outer diameter of 18 mm. It inserted in the cylindrical battery case, and the positive electrode lead body and the negative electrode lead body were welded.
[0063]
Then, 1.0 mol / l LiPF in the battery case₆/ EC + EMC (1 + 3) electrolyte solution [ie, LiPF in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 3₆4.0 mol / l of non-aqueous electrolyte solution] was injected.
[0064]
Next, the opening of the battery case was sealed according to a conventional method, and a cylindrical non-aqueous electrolyte secondary battery having the structure shown in FIG. 3 was produced.
[0065]
The battery shown in FIG. 3 will be schematically described. 1 is the positive electrode and 2 is the negative electrode. However, in FIG. 3, in order to avoid complication, the metal foil or the like used as the base used for manufacturing the positive electrode 1 and the negative electrode 2 is not shown, and the positive electrode 1 and the negative electrode 2 are spirally connected via the separator 3. A spiral electrode body is housed in a battery case 4 made of stainless steel together with the electrolytic solution having the above composition.
[0066]
The battery case 4 also serves as a negative electrode terminal, an insulator 5 is disposed at the bottom thereof, and an insulator 6 is also disposed on the spiral electrode body. A sealing body 8 is disposed in the opening of the battery case 4 via an annular insulating packing 7, and the inside of the battery is sealed by tightening the opening end of the battery case 4 inward. However, the sealing body 8 incorporates an irreversible vent mechanism for discharging the gas generated in the battery to the outside of the battery when the pressure is raised to a certain pressure, and preventing the battery from bursting under high pressure. It is.
[0067]
Example 2
The same chemically synthesized manganese dioxide as in Example 1 was used, and the ratio of the amount of Mn in this chemically synthesized manganese dioxide to the amount of Li in lithium hydroxide monohydrate was 0.50 in molar ratio. A lithium manganese oxide was produced in the same manner as in Example 1 except that the raw materials were mixed together to produce a model cell and a battery. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.03Mn_1.97O_3.94Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 48 ppm. Further, when the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 19 μm and the specific surface area was 1.1 m.²/ G.
[0068]
Example 3
A lithium manganese oxide was produced in the same manner as in Example 1 except that the firing temperature was changed from 800 ° C. to 780 ° C., and a model cell and a battery were produced. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.02Mn_1.98O_3.98Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption analyzer as in Example 1, the Fe content was 43 ppm. Further, when the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 23 μm and the specific surface area was 1.0 m.²/ G.
[0069]
Example 4
A lithium manganese oxide was produced in the same manner as in Example 1 except that the firing temperature was changed from 800 ° C. to 820 ° C., and a model cell and a battery were produced. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.01Mn_1.99O_3.94Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 35 ppm. Further, when the average particle size and specific surface area were measured in the same manner as in Example 1, the average particle size was 16 μm and the specific surface area was 1.2 m.²/ G.
[0070]
Example 5
Lithium manganese oxide as in Example 1 except that chemically synthesized manganese dioxide having a Fe content of 98 ppm in the raw material chemically synthesized manganese dioxide was used and the product lithium manganese oxide was classified to particles of 63 μm or less. Things were manufactured and model cells and batteries were made. When the shape of the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li as in Example 1._1.01Mn_1.99O_3.92Met. Further, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 195 ppm. Further, when the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 32 μm and the specific surface area was 0.6 m.²/ G.
[0071]
Example 6
Lithium manganese oxide as in Example 1 except that the product lithium manganese oxide was classified into particles of 32 μm or less and the mixed gas was supplied at a flow rate of 1.5 liter / min per 100 g of the raw material mixture. And manufactured a model cell and a battery. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.02Mn_1.98O_3.90Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 49 ppm. Further, when the average particle size and specific surface area were measured in the same manner as in Example 1, the average particle size was 8 μm and the specific surface area was 2.3 m.²/ G.
[0072]
Comparative Example 1
Commercially available LiMn₂O_Four(Average particle size 31 μm, specific surface area 0.8 m²Model cell and battery were produced in the same manner as in Example 1 except that / g) was used as the positive electrode active material. Commercially available LiMn₂O_FourWhen observed with an electron microscope in the same manner as in Example 1, the shape was angular as shown in FIG. 2 (electron micrograph at a magnification of 1500 times). Moreover, when Fe content in this spinel type lithium manganese oxide was measured with the atomic absorption analyzer similarly to Example 1, Fe content was 600 ppm.
[0073]
Comparative Example 2
Chemically synthesized manganese dioxide having a Fe content of 512 ppm in the raw chemically synthesized manganese dioxide is used, and the ratio of the amount of Mn in this chemically synthesized manganese dioxide to the amount of Li in lithium hydroxide monohydrate is The lithium manganese oxide was produced in the same manner as in Example 1 except that the raw materials were mixed so that the molar ratio was 0.525, and the product was not classified, and a model cell and a battery were produced. . When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.09Mn_1.91O_3.98Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 957 ppm. Further, when the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 54 μm and the specific surface area was 0.1 m.²/ G.
[0074]
Comparative Example 3
Chemically synthesized manganese dioxide having a Fe content of 329 ppm in the raw material chemically synthesized manganese dioxide is used, and the ratio of the amount of Mn in this chemically synthesized manganese dioxide to the amount of Li in lithium hydroxide monohydrate is The lithium manganese oxide was produced in the same manner as in Example 1 except that the raw materials were mixed so that the molar ratio was 0.525, the firing temperature was changed to 850 ° C., and the product was not classified. Then, a model cell and a battery were produced. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.08Mn_1.92O_3.96Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 643 ppm. Further, when the average particle size and specific surface area were measured in the same manner as in Example 1, the average particle size was 62 μm and the specific surface area was 0.1 m.²/ G.
[0075]
Comparative Example 4
Chemically synthesized manganese dioxide having a Fe content of 481 ppm in the raw chemically synthesized manganese dioxide is used, and the ratio of the amount of Mn in this chemically synthesized manganese dioxide to the amount of Li in lithium hydroxide monohydrate is The lithium manganese oxide was produced in the same manner as in Example 1 except that the raw materials were mixed so that the molar ratio was 0.525, the firing temperature was changed to 750 ° C., and the product was not classified. Then, a model cell and a battery were produced. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.08Mn_1.92O_3.93Met. Furthermore, when the Fe content in the spinel type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 918 ppm. Further, when the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 60 μm and the specific surface area was 0.1 m.²/ G.
[0076]
Comparative Example 5
Lithium manganese oxide was produced in the same manner as in Example 1 except that the flow rate of the mixed gas of argon gas and oxygen gas was changed to 0.1 liter / min per 100 g of the raw material mixture. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, the obtained lithium manganese oxide was LiMn.₂O_FourAnd Li₂MnO_ThreeIn addition, Mn as a reaction intermediate product₂O_ThreeThus, lithium manganese oxide having only a spinel structure was not obtained.
[0077]
Comparative Example 6
Lithium manganese oxide was produced in the same manner as in Example 1 except that the flow rate of the mixed gas of argon gas and oxygen gas was changed to 0.6 liter / min per 100 g of the raw material mixture. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, the obtained lithium manganese oxide was LiMn.₂O_FourAnd Li₂MnO_ThreeIn addition, Mn as a reaction intermediate product₂O_ThreeThus, lithium manganese oxide having only a spinel structure was not obtained.
[0078]
Comparative Example 7
Electro-synthesized manganese dioxide (45 μm previously classified as a raw material of Mn (
Fe content of the electrolytically synthesized manganese dioxide is 205 ppm), and the ratio of the Mn amount of the electrolytically synthesized manganese dioxide to the Li amount in the lithium hydroxide hydrate is 0.525 in molar ratio. The lithium manganese oxide was produced in the same manner as in Example 1 except that the raw materials were mixed so that the firing temperature was 750 ° C. and the product was not classified, and a model cell and a battery were produced. . When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a lithium manganese oxide having a spinel structure. Moreover, when observed with the electron microscope similarly to Example 1, the shape had the same angular shape as the comparative example 1. Moreover, when the composition of Li, Mn, and O was measured with an atomic absorption analyzer as in Example 1, the composition of the manufactured lithium manganese oxide was Li_1.10Mn_1.90O_3.92Met. Furthermore, when the Fe content in the spinel-type lithium manganese oxide was measured with an atomic absorption analyzer in the same manner as in Example 1, the Fe content was 413 ppm. Further, when the average particle size and specific surface area were measured in the same manner as in Example 1, the average particle size was 37 μm and the specific surface area was 0.5 m.²/ G.
[0079]
The discharge capacity and load characteristics were examined for each model cell produced as described above, and the cycle characteristics and low temperature discharge characteristics were examined for the batteries. The results are shown in Table 1. The discharge capacity of each model cell was 4.3 Vvs. Li / Li⁺After charging to 0.5 mA / cm in an environment of 20 ° C.²Current density of 3.0 Vvs. Li / Li⁺The discharge capacity at the time of discharging was measured, and it was shown in terms of the discharge capacity per weight of the positive electrode active material. The load characteristic is 4.0 mA / cm²Current density of 3.0 Vvs. Li / Li⁺Discharge capacity when discharged to 0.5 mA / cm²Current density of 3.0 Vvs. Li / Li⁺Ratio of discharge capacity when discharged to [4.0 mA / cm²Discharge capacity at a current density of) / (0.5 mA / cm²Discharge capacity at current density) × 100].
[0080]
Moreover, after charging to 4.2V with a constant current of 1A in an environment of 20 ° C., the cycle characteristics were charged by a constant voltage method, and charged so that the total charging time was 2.5 hours. In a cycle test when discharging to 3.0 V at a constant current of 1 A under an environment of 20 ° C., the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle [(discharge capacity at the 500th cycle) / ( The discharge capacity at the first cycle) × 100] was obtained and used as the capacity retention, and the capacity retention at the 500th cycle was evaluated.
[0081]
Furthermore, the discharge characteristics at low temperatures are 3 for a discharge capacity when discharged to 3.0 V at a constant current of 0.2 A in an environment of −20 ° C. and a constant current of 0.2 A in an environment of 20 ° C. Evaluation was carried out at a ratio [(discharge capacity at −20 ° C.) / (Discharge capacity at 20 ° C.) × 100] with the discharge capacity when discharged to 0.0 V. When measuring the discharge characteristics at low temperatures, the charging conditions are as follows. At any temperature, the battery is charged at a constant current of 1 A to 4.2 V in an environment of 20 ° C., then charged by a constant voltage method. The battery was charged so that the total was 2.5 hours. Thereafter, the battery was left at a predetermined discharge temperature for 4 hours, and then a discharge test was started.
[0082]
[Table 1]

[0083]
As shown in Table 1, Examples 1 to 6 had a large discharge capacity, a high capacity, a large capacity retention at the 500th cycle, and excellent cycle characteristics as compared with Comparative Examples 1 to 7. . As can be seen from the fact that the discharge capacities of Examples 1 to 6 are large as described above, the spinel type lithium manganese oxide used in Examples 1 to 6 is spherical or elliptical particles. It is thought that the filling property in the production was also good. In Examples 1 to 6, the discharge capacity was large and the load characteristics were excellent. This is considered to be because in Examples 1 to 6, spinel type lithium manganese oxide having an Fe content of 200 ppm or less was used as the positive electrode active material. Furthermore, Examples 1-6 were excellent also in the discharge characteristic at the time of low temperature. In Examples 1 to 6, the average particle diameter is in the range of 1 to 45 μm and the specific surface area is 0.5 to 3 m.²This is considered to be due to the use of a spinel type lithium manganese oxide in the range of / g as the positive electrode active material.
[0084]
In contrast, the composition is the general formula Li_xMn_yO_4-z(When x + y = 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦ 0.15, where x is a value when assembling the battery, and 0 <x ≦ 1.05 during charging and discharging. Comparative Examples 1 to 7 using lithium manganese oxides deviating from the above range as the positive electrode active material had a smaller discharge capacity and poor cycle characteristics than Examples 1 to 6. . In addition, as in Comparative Examples 2 to 7, when the manufacturing conditions deviated from the present invention, lithium manganese oxide having a large discharge capacity and excellent cycle characteristics as in the present invention could not be produced. . In Comparative Examples 2 to 4 in which a spinel type lithium manganese oxide having a Fe content of more than 200 ppm was used as the positive electrode active material, the load characteristics were poor. In particular, Comparative Example 5 and Comparative Example 6 were lithium manganese oxides having only a spinel structure. Could not get. Further, in Comparative Examples 1 to 7, the average particle diameter is outside the range of 1 to 45 μm, and the specific surface area is also 0.5 to 3 m.²Since it was out of the range of / g, the discharge characteristics at low temperature were poor.
[0085]
【The invention's effect】
As described above, in the present invention, the general formula Li_xMn_yO_4-z(When x + y = 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦ 0.15, where x is a value when assembling the battery, and 0 <x ≦ 1.05 during charging and discharging. The cathode active material is composed of a spherical or elliptical spinel type lithium manganese oxide represented by the following formula: It was possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can impart high capacity and excellent cycle characteristics to the electrolyte secondary battery. In the present invention, the spinel lithium manganese oxide has a Fe content of 200 ppm or less, and the spinel lithium manganese oxide having the Fe content of 200 ppm or less is used as the positive electrode active material, thereby reducing the discharge capacity. A large non-aqueous electrolyte secondary battery having excellent load characteristics could be provided. Furthermore, in this invention, the average particle diameter of the said spinel type lithium manganese oxide is made into the range of 1-45 micrometers, and a specific surface area is 0.5-3 m.²By using it as a positive electrode active material within the range of / g, a non-aqueous electrolyte secondary battery having excellent discharge characteristics at low temperatures could be provided.
[0086]
In addition, since the spinel type lithium manganese oxide of the present invention is a spherical or elliptical particle, it has a good filling property in the production of the positive electrode, and is composed of abundant and inexpensive manganese as a constituent element. It is suitable for production and has great industrial significance.
[Brief description of the drawings]
FIG. 1 is an electron micrograph of 1510 times magnification showing the particle structure of the spinel type lithium manganese oxide of the present invention.
FIG. 2 Commercially available LiMn₂O_FourIt is an electron micrograph of the magnification 1500 times which shows the particle structure.
FIG. 3 is a partial cross-sectional perspective view schematically showing an example of a non-aqueous electrolyte secondary battery.
[Explanation of symbols]
1 Positive electrode
2 Negative electrode
3 Separator
4 Battery case
5 Insulator
6 Insulator
7 Insulation packing
8 Sealing body

Claims (4)

Manufactured using chemically synthesized manganese dioxide having an Fe content of 98 ppm or less as a manganese source. When general formula Li _x Mn _y O _4-z (x + y = 3.00, 1.00 ≦ x ≦ 1.05, 0 < z ≦ 0.15, provided that, x is a value at the time of battery assembly, expressed in charging and discharging upon a value that varies from 0 <x ≦ 1.05), spherical or ellipsoidal shape, Fe content A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a spinel type lithium manganese oxide having a content of 200 ppm or less . ^{2. The} positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the spinel-type lithium manganese oxide has an average particle size of 1 to 45 μm and a specific surface area of 0.5 to ³ m ² / g. . The mixing ratio of chemically synthesized manganese dioxide having an Fe content of 98 ppm or less and lithium salt is Li / Mn ≦ 0.50 in terms of the molar ratio of Li and Mn, and a mixed gas of inert gas and oxygen gas is used per 100 g of the raw material mixture. By firing at 780 to 820 ° C. while supplying at a flow rate of 1 liter / min or more, when the general formula Li _x Mn _y O _4-z (x + y = 3.00, 1.00 ≦ x ≦ 1. 05, 0 <z ≦ 0.15, where x is a value at the time of battery assembly, and is a value that changes in the range of 0 <x ≦ 1.05 during charging and discharging). A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a spinel type lithium manganese oxide. Non-aqueous electrolyte secondary battery characterized by using a positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 or 2.

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