JP3624663B2 - battery - Google Patents

Description

【００７２】
【表２】

【００７３】
【表３】

【００７４】
【表４】

【００７５】
【表５】

【００７６】
【表６】

【００７７】
【表７】

【００７８】
【表８】

【００７９】
（比較例５）
正極材料として前記表中に比較例５として示す材料を使用し、導電剤として黒鉛を結着剤としてポリフッ化ビニリデンを重量比で８８：７：５となるように秤量，らいかい機で３０分混練後、厚さ２０μのアルミ箔の両面に塗布した。負極材料として人造黒鉛を９３重量％，結着剤としてポリフッ化ビニリデンを７重量％調製した合剤を用い、厚さ３０μの銅箔の両面に塗布した。
【００８０】
実施例５と同様にして電池を作製した。容量，寿命，レート特性，過充電試験，釘刺し試験を評価した。結果を表２に示す。実施例５と比較して極端に低い特性が存在する。
【００８１】
【発明の効果】
本発明によれば、二次電池用正極材料の高容量化，長寿命化，レート特性や、高温特性，安全性の改善の電池特性の一部又は全部の面で優れた特性を得ることができる。
【図面の簡単な説明】
【図１】格子体積及び格子定数の変化を示す図である。
【図２】電子伝導率測定セルの概略図である。
【図３】伝導率の温度依存性を示す図である。
【図４】充放電試験セルの概略図である。
【図５】実施例１の正極材料を用いた実施例４のｃ軸格子定数の変化を示す図である。
【図６】実施例１の正極材料を用いた実施例４のｃ軸格子定数／ａ軸格子定数比の変化を示す図である。
【図７】電池構造の一例を示す図である。
【図８】比較例１の正極材料を用いた比較例４のｃ軸格子定数の変化を示す図である。
【図９】比較例１の正極材料を用いた比較例４のｃ軸格子定数／ａ軸格子定数の変化を示す図である。
【図１０】比較例２の正極材料を用いた比較例４のｃ軸格子定数の変化を示す図である。
【図１１】比較例２の正極材料を用いた比較例４のｃ軸格子定数／ａ軸格子定数比の変化を示す図である。
【符号の説明】
２１…端子、２２…Ａｇペースト、２３…正極ペレット、２４…ステンレス鋼板、２５…ポリエチレンフィルム、２６…ラミネートフィルム、４１，７１…セパレータ、４２…電解液、４３…参照極、４４，７２…正極、４６…対極、７３…負極、７４…電池缶、７５…電池内蓋、７６…負極端子、７７…正極端子、７８…フィルム、７９…安全弁。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery.
[0002]
[Prior art]
In recent years, secondary batteries have become one of the essential components that are indispensable as power sources for personal computers and mobile phones, and as power sources for electric vehicles and power storage.
[0003]
As a request that requires mobile communication (mobile computing) such as a portable computer (including what is called a pen computer) and a portable information terminal (Personal Digital Assistant, Personal Intelligent Communicator, or Handheld Communicator), It can be reduced in size and weight. However, it is difficult to reduce the size and weight of the system because the power consumed by the backlight and drawing control of the LCD panel is high, and the capacity of the secondary battery is still insufficient. It is in.
[0004]
Furthermore, with the growing global environmental problems, electric vehicles that emit no exhaust gas or noise are attracting attention. However, current batteries have low energy density and low power density, which causes problems such as short travel distance, poor acceleration, narrow space in the vehicle, and poor vehicle stability.
[0005]
Among secondary batteries, lithium secondary batteries using a non-aqueous electrolyte are attracting attention because they are expected to have high voltage, light weight, and high energy density. The positive electrode material of the secondary battery is made of conductive polymer such as polyaniline, polyacene, polyparaphenylene, or Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x FeO ₂ , V ₂ O ₅ , Cr ₂ O ₅ , MnO ₂ Transition metal oxides such as TiS ₂ , MoS ₂ The chalcogenite compounds such as are representative. In particular, Li disclosed in JP-A-55-136131 _x CoO ₂ , Li _x NiO ₂ Since a secondary battery positive electrode such as the above has an electromotive force of 4 V or more when Li metal is used as a negative electrode, a high energy density can be expected. However, in reality, the capacity that can actually be used is still low or the life is short, and overperformance, self-discharge characteristics and high-temperature characteristics at the time of charging / discharging are not yet sufficient. In addition, the positive electrode active material decomposes exothermically during overcharge, causing thermal runaway, and the battery ignites and explodes.
[0006]
Conventionally, various active material compositions have been proposed in order to achieve higher capacity and longer life of the positive electrode. For example, for improving the cycle characteristics, the positive electrode active material has the chemical formula Li _x MO ₂ (M represents one or more elements selected from Co, Ni, Fe, and Mn) (Japanese Patent Laid-Open No. 2-306022), or a chemical formula Li _x M _y Ge _z O _p (M is one or more transition metal elements selected from Co, Ni and Mn, 0.9 ≦ x ≦ 1.3, 0.8 ≦ y ≦ 2.0, 0.01 ≦ z ≦ 0.2, 2 (Japanese Patent Laid-Open No. 7-29603) has been disclosed. In order to improve cycle characteristics and self-discharge characteristics, A _x M _y N _z O ₂ (A is at least one selected from alkali metals, M is a transition metal, N represents at least one selected from the group of Al, In, and Sn, and 0.05 ≦ x ≦ 1.10. , 0.85 ≦ y ≦ 1.00, 0.001 ≦ z ≦ 0.10) (Japanese Patent Laid-Open No. 7-176302), and also improves the capacity and cycle characteristics. As a thing, Li _y Ni _(1-x) M _x O ₂ (M is at least one element selected from the group consisting of Cu, Zn, Nb, Mo and W, and a composite oxide represented by 0 <x <1, 0.9 ≦ y ≦ 1.3) is used. (Kaihei 6-283174) and the like. In addition, for improving the cycle characteristics and increasing the load characteristics, the chemical formula Li _x Mg _y Co _z Ni _1-yz O _a (If 0.95 ≦ x ≦ 1.05, 0.02 ≦ z ≦ 0.15, 0.003 <y <0.02, if z <0.02, 0.003 <y <0.05. , A = 2) (Japanese Patent Laid-Open No. 8-185863) is disclosed.
[0007]
[Problems to be solved by the invention]
Cathode active material with chemical formula Li _x MO ₂ When the lithium-containing composite oxide represented by (M represents one or more elements selected from Co, Ni, Fe, and Mn) is used, the cycle life is improved. However, it is difficult to say that the characteristics are sufficient in terms of capacity. In addition, there is a disadvantage that the voltage is lowered. A _x M _y N _z O ₂ (A is at least one selected from alkali metals, M is a transition metal, N represents at least one selected from the group of Al, In, and Sn, and 0.05 ≦ x ≦ 1.10. , 0.85 ≤ y ≤ 1.00, 0.001 ≤ z ≤ 0.10), the cycle life is similarly improved. Since the capacity that can be obtained decreases, the capacity cannot be increased. Cathode active material with chemical formula Li _x M _y Ge _z O _p (M is one or more transition metal elements selected from Co, Ni and Mn, 0.9 ≦ x ≦ 1.3, 0.8 ≦ y ≦ 2.0, 0.01 ≦ z ≦ 0.2, 2 When the composite oxide represented by .ltoreq..ltoreq.p.ltoreq.4.5) is used, the capacity and cycle life are improved. However, thermal runaway reaction during overcharge cannot be suppressed. Li _y Ni _(1-x) M _x O ₂ (Where M is at least one element selected from the group consisting of Cu, Zn, Nb, Mo, and W, 0 <x <1, 0.9 ≦ y ≦ 1.3). Chemical formula Li _x Mg _y Co _z Ni _1-yz O _a (If 0.95 ≦ x ≦ 1.05, 0.02 ≦ z ≦ 0.15, 0.003 <y <0.02, if z <0.02, 0.003 <y <0.05. , A = 2). It is desirable to have an effective improvement method in terms of all battery characteristics such as higher capacity, longer life, reduction of overvoltage during charge / discharge, rate characteristics, self-discharge characteristics, high temperature characteristics, and safety improvements for secondary battery positive electrode materials. It is.
[0008]
An object of the present invention is to improve part or preferably all of these battery characteristics of a positive electrode material for a secondary battery.
[0009]
[Means for Solving the Problems]
In the battery and the positive electrode of the present invention, Li, O, Mg as essential elements constituting the positive electrode active material, and a layered or zigzag layered LiMeO ₂ And Me has at least one selected from Mn, Co, Ni, and Fe, and LiMeO ₂ Mg is present at the Li position in the structure. As a layered structure, for example, α-NaFeO ₂ There is a hexagonal layered structure indicated by the mold. This is α-NaFeO ₂ In this structure, cations are regularly arranged alternately in the vertical direction of cubic close-packing of type oxide ions. The zigzag layered structure includes an orthorhombic zigzag layered structure. This is because Me ions occupy half of the octahedral positions in the cubic close packed array, ₆ An octahedron shares a ridge to form a double chain, and this double chain shares a ridge with each other and is a layered structure consisting of a two-dimensional surface connected in a zigzag manner. As a method for confirming whether Mg is present at the Li position, it can be obtained by an EXAFS measurement, a neutron diffraction measurement, an X-ray diffraction measurement, and an analytical method such as a Rietveld or FEFF. Mg ²⁺ The ion radius of Li ⁺ Smaller than the ionic radius of Mn ³⁺ , Co ³⁺ , Ni ³⁺ , Fe ³⁺ It is larger than the ion radius. Therefore, if Mg is present at the Li position, the lattice constant and the lattice volume are contracted compared to when Mg is not present or when the amount of Mg is small, and Mg is present at the Me position. For example, the lattice constant and the lattice volume expand as compared with the case where Mg is not present or the amount of Mg is small. From these facts, the position where Mg is present can be confirmed by the change in lattice constant and lattice volume.
[0010]
In order to synthesize such that Mg is present at the Li position, a method of directly synthesizing Li and Mg is preferable. The most avoidable method is to prepare a composite material of Me and Mg obtained by directly synthesizing Me and Mg in a wet manner. In the method of synthesizing using this raw material, Mg is likely to be mixed at the Me position, so that it is difficult to make Mg present at the Li position.
[0011]
As a raw material for Mg, it is desirable to use at least one selected from magnesium nitrate, magnesium sulfate, magnesium carbonate, magnesium oxalate, magnesium oxide, and magnesium chloride. Further, it is obtained by finally mixing the magnesium raw material and all other raw materials except for magnesium, followed by firing and / or pulverization and / or classification.
[0012]
In the battery and the positive electrode of the present invention, Li, O, Mg as essential elements constituting the positive electrode active material, and a layered or zigzag layered LiMeO ₂ Having a structure, Me includes at least one selected from Mn, Co, Ni, and Fe, and the positive electrode active material has an electronic conductivity of −1 ° C. or lower at −40 ° C. or lower, preferably 100 S / m It is more than m. In the conventional positive electrode active material, the electronic conductivity at −40 ° C. or less was as extremely low as 0.1 S / m 2 or less, whereas in the positive electrode active material of the present invention, an extremely large value was exhibited as compared with the conventional one.
[0013]
Further, as the positive electrode active material, the change rate δσ / δT of the active material with respect to the temperature is 0 or negative in the temperature range of 50 ° C. to −196 ° C., preferably 40 ° C. to −20 ° C. It is characterized by being 0 or negative in the range. In the conventional positive electrode active material, the electron conductivity is lower on the low temperature side of −20 ° C. or lower than the high temperature side of 40 ° C. or higher, and the change rate δσ / δT of the active material with respect to temperature is positive. In contrast to the semiconducting conductivity, the positive electrode active material of the present invention has a higher or lower electron conductivity on the low temperature side of −20 ° C. or lower than the high temperature side of 40 ° C. or higher. The rate of change δσ / δT with respect to temperature of the electronic conductivity σ is 0 or negative, indicating metallic conductivity.
[0014]
Further, the battery and the positive electrode of the present invention have Li, O, Mg as essential elements as elements constituting the positive electrode active material, and are layered or zigzag layered LiMeO. ₂ From a state in which Me has at least one selected from Mn, Co, Ni, and Fe and 100% of the battery capacity is charged to a state in which 100% of the battery capacity is discharged C-axis lattice constant of c1 _max And the minimum value c1 _min Rate of change with (c1 _max -C1 _min ) / C1 _min Is 0.03 or less. Rate of change (c1 _max -C1 _min ) / C1 _min However, when it is larger than 0.03, the stress of expansion / contraction of the lattice due to charge / discharge increases, so that the particles collapse and the cycle life is short.
[0015]
Furthermore, the battery and the positive electrode of the present invention have Li, O, Mg as essential elements as elements constituting the positive electrode active material, and are layered or zigzag layered LiMeO. ₂ Having a structure, Me includes at least one selected from Mn, Co, Ni, Fe, and Li _0.5 MeO ₂ Maximum value of c-axis lattice constant of c2 _max And Li _0.2 MeO ₂ C2 lattice constant c2 _min Rate of change with (c2 _max -C2 _min ) / C2 _min Is 0.01 or less. Li _0.5 MeO ₂ Then, LiMeO ₂ Since the abundance of Li is small compared to, a repulsive force acts between the O layer and the O layer, and the c-axis lattice constant expands. At this time, a plurality of LiMeOs having different types, different reactivities, or different crystal structures. ₂ If a phase is present, the maximum value is selected from the c-axis lattice constants, and this is c2 _max And On the other hand, Li _0.2 MeO ₂ Then Li _0.5 MeO ₂ Compared to ⁴⁺ Has a large ion radius ³⁺ The c-axis lattice constant contracts in the opposite direction. Also at this time, a plurality of LiMeOs having different types, different reactivities, or different crystal structures. ₂ When a phase exists, the minimum value is selected from the c-axis lattice constants, and this is expressed as c2 _min And In the present invention, the rate of change (c2) determined from these two values. _max -C2 _min ) / C2 _min Is 0.01 or less. If it is greater than 0.01, the stress of expansion and contraction of the lattice due to charge / discharge increases, so that the particle collapse is significant and the cycle life is short.
[0016]
Further, the battery and the positive electrode of the present invention have Li, O, Mg as essential elements as elements constituting the positive electrode active material, and are layered or zigzag layered LiMeO. ₂ And Me has at least one selected from Mn, Co, Ni, and Fe, and Li _0.5 MeO ₂ The maximum value of the ratio of the c-axis lattice constant c1 to the a-axis lattice constant a1 (c1 / a1) _max And Li _0.2 MeO ₂ Minimum value of the ratio of the c-axis lattice constant c2 to the a-axis lattice constant a2 (c2 / a2) _min The difference is within 0.1. The smaller the ratio of the c-axis lattice constant c to the a-axis lattice constant a, that is, the smaller the change in c / a, the smaller the change in the lattice volume, and the more the crystal stress due to repeated charge / discharge reactions is suppressed. In particular, the difference between the maximum value and the minimum value of c / a is preferably within 0.1. Li _0.5 MeO ₂ The maximum value of the ratio of the c-axis lattice constant c1 to the a-axis lattice constant a1 (c1 / a1) _min And Li _0.2 MeO ₂ Minimum value of the ratio of the c-axis lattice constant c2 to the a-axis lattice constant a2 (c2 / a2) _min When the difference from the above exceeds 0.1, the stress of expansion and contraction of the lattice due to charge / discharge increases, so that the particle collapse is remarkable and the cycle life is short.
[0017]
(1) The battery and positive electrode of the present invention have the general formula Li _w Mg _v Ni _x M _y N _z O ₂ (However, M is at least one selected from Mn, Co, and Fe, and N is at least one selected from Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B. Represents seeds, w, v, x, y, z are 0 ≦ w ≦ 1.2, 0.001 ≦ v ≦ 0.02, 0.5 ≦ x <0.85, 0.05 ≦ y ≦ 0, respectively. .5, 0 ≦ z ≦ 0.2)). Preferably, w, v, x, y, z are 0.2 ≦ w ≦ 1.15, 0.002 ≦ v ≦ 0.015, 0.7 ≦ x <0.85, 0.05 ≦ y ≦ 0, respectively. .25, 0.01 ≦ z ≦ 0.15, and more preferably w, v, x, y, and z are 0.2 ≦ w ≦ 1.05, 0.008 ≦ v ≦ 0.012, respectively. , 0.75 ≦ x ≦ 0.82, 0.05 ≦ y ≦ 0.15, 0.05 ≦ z ≦ 0.15.
[0018]
Since the novel positive electrode active material of the present invention has Mg at the position of Li, w should not be able to take a value of 1 or more, but actually Li is lithium carbonate, lithium oxide, By-products such as lithium hydroxide are easily formed, and as a result, the amount of Li determined by chemical analysis may take a value larger than 1. However, these excess Lis only cover the positive electrode active material, and LiMeO ₂ It is not incorporated in the structure, and has a structure in which Mg is present at the Li position.
[0019]
The novel positive electrode active material of the present invention has the general formula Li _w Mg _v Ni _x M _y N _z O ₂ It has a layered structure. The crystal may change partly in the process of charge and discharge, but mainly maintains hexagonal crystal and α-NaFeO ₂ Take the structure. The value of w representing the amount of Li varies depending on the state of charge and discharge, and the range is 0 ≦ w ≦ 1.2, preferably 0.2 ≦ w ≦ 1.15, and more preferably 0. .2 ≦ w ≦ 1.05. That is, Li ion deintercalation occurs due to charging and the value of w decreases, and Li ion intercalation occurs due to discharge and the value of w increases. If the amount of Li is greater than 1.2, by-products such as lithium carbonate, lithium oxide, and lithium hydroxide generated during the firing process will increase too much, and these materials will be used in the production of electrodes. The electrode cannot be produced successfully. In order to produce an electrode successfully, the smaller the by-products, the better. The value of w is 1.2 or less, desirably 1.15 or less, and more desirably 1.05 or less.
[0020]
Further, the value of v representing the amount of Mg does not vary due to charging or discharging, but is in the range of 0.001 ≦ v <0.02, preferably in the range of 0.002 ≦ v ≦ 0.015, and more preferably Is in the range of 0.008 ≦ v ≦ 0.012. When the value of v is less than 0.001, the effect of Mg is not sufficiently exhibited, the cycleability in deep charge and deep discharge is poor, and the capacity is also unfavorable. On the other hand, when the value of v exceeds 0.02, a single phase cannot be obtained, and a low-capacity phase appears. The most desirable value of v that can sufficiently exhibit the effect of Mg and obtain a high capacity is in the range of 0.008 ≦ v ≦ 0.012.
[0021]
The value of x representing the amount of Ni is in the range of 0.5 ≦ x <0.85, preferably in the range of 0.7 ≦ x <0.85, and more preferably in the range of 0.75 ≦ x ≦ 0. .82 range. When the value of x is less than 0.5, the capacity is remarkably lowered, which is not preferable. Moreover, when the value of x is 0.85 or more, the cycle characteristics in deep charge and deep discharge are poor, which is not preferable. The most desirable value of x that provides high capacity and good cycle performance in deep charge and deep discharge is in the range of 0.75 ≦ x ≦ 0.82.
[0022]
M is at least one selected from Mn, Co and Fe, and the value of y does not vary depending on the state of charge and discharge, and the range is 0.05 ≦ y ≦ 0.5, preferably 0.05 ≦ y ≦ 0.25, more preferably 0.05 ≦ y ≦ 0.15. When the value of y is less than 0.05, the effect of M is not sufficiently exhibited, cycle characteristics in deep charge and deep discharge are poor, thermal stability is poor, and safety is inferior. Further, when the value of y exceeds 0.5, the capacity is lowered, which is not preferable. The most desirable value of y that can sufficiently exhibit the effect of M and obtain a high capacity is in the range of 0.05 ≦ y ≦ 0.15.
[0023]
N is at least one selected from Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, B, and preferably Si, Al, Ca, Cu, Sn, P, In, At least one selected from B, more preferably at least one selected from Si, Al, P, In, and B, and most preferably at least one selected from Si, Al, P, and B It is. The value of z does not vary depending on the state of charge and discharge, and the range is 0 ≦ z ≦ 0.2, preferably 0.01 ≦ z ≦ 0.15, and more preferably 0.05 ≦ z. The range is z ≦ 0.15. When the value of z exceeds 0.2, the overvoltage at the time of charging / discharging is high, a single phase cannot be obtained, and a phase with a low capacity appears, so that the capacity is lowered, which is not preferable. The most desirable value of z that can sufficiently exhibit the effect of N and obtain a high capacity is in the range of 0.05 ≦ z ≦ 0.15.
[0024]
(2) The battery and the positive electrode of the present invention have the general formula Li _w Mg _v Co _x N _z O ₂ (However, N represents at least one selected from Ni, Mn, Fe, Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B, w, v, x, z represents a number of 0 ≦ w ≦ 1.2, 0.001 ≦ v <0.02, 0.5 ≦ x <0.85, 0 ≦ z ≦ 0.5). It is characterized by using. Preferably, w, v, x, and z are 0.2 ≦ w ≦ 1.15, 0.002 ≦ v ≦ 0.015, 0.7 ≦ x <0.85, 0.01 ≦ z ≦ 0.15, respectively. More preferably, w, v, x, y, and z are 0.2 ≦ w ≦ 1.05, 0.008 ≦ v ≦ 0.012, 0.75 ≦ x ≦ 0.82, 0, respectively. .05 ≦ z ≦ 0.15.
[0025]
Since the novel positive electrode active material of the present invention has Mg at the position of Li, w should not be able to take a value of 1 or more, but actually Li is lithium carbonate, lithium oxide, By-products such as lithium hydroxide are easily formed, and as a result, the amount of Li determined by chemical analysis may take a value larger than 1. However, these excess Lis only cover the positive electrode active material, and LiMeO ₂ It is not incorporated in the structure, and has a structure in which Mg is present at the Li position.
[0026]
The novel positive electrode active material of the present invention has the general formula Li _w Mg _v Co _x N _z O ₂ It has a layered structure. The crystal may change partly in the process of charge and discharge, but mainly maintains hexagonal crystal and α-NaFeO ₂ Take the structure. The value of w representing the amount of Li varies depending on the state of charge and the state of discharge, and the range is 0 ≦ w ≦ 1.2. The range is preferably 0.2 ≦ w ≦ 1.15, and more preferably the range is 0.2 ≦ w ≦ 1.05. That is, Li ion deintercalation occurs due to charging and the value of w decreases, and Li ion intercalation occurs due to discharge and the value of w increases. If the amount of Li is greater than 1.2, the amount of by-products such as lithium carbonate, lithium oxide, and lithium hydroxide produced during the firing process will increase so much that these materials are used in the production of electrodes. The electrode cannot be successfully produced by reacting with the agent. In order to produce an electrode successfully, the smaller the by-products, the better. The value of w is 1.2 or less, desirably 1.15 or less, and more desirably 1.05 or less.
[0027]
Further, the value of v representing the amount of Mg does not vary due to charging or discharging, but is in the range of 0.001 ≦ v <0.02, preferably in the range of 0.002 ≦ v ≦ 0.015, and more preferably Is in the range of 0.008 ≦ v ≦ 0.012. When the value of v is less than 0.001, the effect of Mg is not sufficiently exhibited, the cycleability in deep charge and deep discharge is poor, and the capacity is also unfavorable. On the other hand, when the value of v exceeds 0.02, a single phase cannot be obtained, and a low-capacity phase appears. The most desirable value of v that can sufficiently exhibit the effect of Mg and obtain a high capacity is in the range of 0.008 ≦ v ≦ 0.012.
[0028]
The value of x representing the amount of Co is in the range of 0.5 ≦ x <0.85, preferably in the range of 0.7 ≦ x <0.85, and more preferably in the range of 0.75 ≦ x ≦ 0. .82 range. When the value of x is less than 0.5, the capacity is remarkably lowered, which is not preferable. Moreover, when the value of x is 0.85 or more, the cycle characteristics in deep charge and deep discharge are poor, which is not preferable. The most desirable value of x that provides high capacity and good cycle performance in deep charge and deep discharge is in the range of 0.75 ≦ x ≦ 0.82.
[0029]
N is at least one selected from Ni, Mn, Fe, Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B, preferably Ni, Mn, Fe, Si, At least one selected from Al, Ca, Cu, Sn, P, In, and B, more preferably at least one selected from Ni, Mn, Fe, Si, Al, P, In, and B Most preferably, it is at least one selected from Si, Al, P, and B. The value of z does not vary depending on the state of charge and discharge, and the range is 0 ≦ z ≦ 0.5, preferably 0.01 ≦ z ≦ 0.15, and more preferably 0.05 ≦ z. The range is z ≦ 0.15. If the value of z exceeds 0.5, the overvoltage at the time of charging / discharging is high, a single phase cannot be obtained, and a phase with a low capacity appears. The most desirable value of z that can sufficiently exhibit the effect of N and obtain a high capacity is in the range of 0.05 ≦ z ≦ 0.15.
[0030]
(3) Furthermore, the battery and the positive electrode of the present invention have the general formula Li _w Mg _v Mn _x N _z O ₂ (However, N represents at least one selected from Ni, Co, Fe, Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B, w, v, x, z represents a number of 0 ≦ w ≦ 1.2, 0.001 ≦ v <0.02, 0.5 ≦ x <0.85, and 0 ≦ z ≦ 0.5, respectively. It is characterized by using. Preferably, w, v, x, and z are 0.2 ≦ w ≦ 1.15, 0.002 ≦ v ≦ 0.015, 0.7 ≦ x <0.85, 0.01 ≦ z ≦ 0.15, respectively. More preferably, w, v, x, and z are 0.2 ≦ w ≦ 1.05, 0.008 ≦ v ≦ 0.012, 0.75 ≦ x ≦ 0.82, 0.05, respectively. It is the range of ≦ z ≦ 0.15.
[0031]
Since the novel positive electrode active material of the present invention has Mg at the position of Li, w should not be able to take a value of 1 or more, but actually Li is lithium carbonate, lithium oxide, By-products such as lithium hydroxide are easily formed, and as a result, the amount of Li determined by chemical analysis may take a value larger than 1. However, these excess Lis only cover the positive electrode active material, and LiMeO ₂ It is not incorporated in the structure, and has a structure in which Mg is present at the Li position.
[0032]
The novel positive electrode active material of the present invention has the general formula Li _w Mg _v Mn _x N _z O ₂ The value of w representing the amount of Li varies depending on the charge state and the discharge state, and the range is 0 ≦ w ≦ 1.2, preferably 0.2 ≦ w ≦ 1.15. More preferably, the range is 0.2 ≦ w ≦ 1.05. That is, Li ion deintercalation occurs due to charging and the value of w decreases, and Li ion intercalation occurs due to discharge and the value of w increases. If the amount of Li is greater than 1.2, by-products such as lithium carbonate, lithium oxide, and lithium hydroxide generated during the firing process will increase too much, so these materials will be used in the production of electrodes. The electrode cannot be successfully produced by reacting with the agent. In order to successfully produce an electrode, the smaller the amount of by-products, the better. The value of w is 1.2 or less, desirably 1.15 or less, and more desirably 1.05 or less.
[0033]
Further, the value of v representing the amount of Mg does not vary due to charging or discharging, but is in the range of 0.001 ≦ v <0.02, preferably in the range of 0.002 ≦ v ≦ 0.015, and more desirably. Is in the range of 0.008 ≦ v ≦ 0.012. When the value of v is less than 0.001, the effect of Mg is not sufficiently exhibited, the cycleability in deep charge and deep discharge is poor, and the capacity is also unfavorable. On the other hand, when the value of v exceeds 0.02, a single phase cannot be obtained, and a low-capacity phase appears. The most desirable value of v that can sufficiently exhibit the effect of Mg and obtain a high capacity is in the range of 0.008 ≦ v ≦ 0.012.
[0034]
The value of x representing the amount of Mn is in the range of 0.5 ≦ x <0.85, preferably in the range of 0.7 ≦ x <0.85, and more preferably in the range of 0.75 ≦ x ≦ 0. .82 range. When the value of x is less than 0.5, the capacity is remarkably lowered, which is not preferable. Moreover, when the value of x is 0.85 or more, the cycle characteristics in deep charge and deep discharge are poor, which is not preferable. The most desirable value of x that provides high capacity and good cycle performance in deep charge and deep discharge is in the range of 0.75 ≦ x ≦ 0.82.
[0035]
N is at least one selected from Ni, Co, Fe, Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B, preferably Ni, Co, Fe, Si, At least one selected from Al, Ca, Cu, Sn, P, In, and B, more preferably at least one selected from Ni, Co, Fe, Si, Al, P, In, and B Most preferably, it is at least one selected from Si, Al, P, and B. The value of z does not vary depending on the state of charge and discharge, and the range is 0 ≦ z ≦ 0.5, preferably 0.01 ≦ z ≦ 0.15, and more preferably 0.05 ≦ z. The range is z ≦ 0.15. If the value of z exceeds 0.5, the overvoltage at the time of charging / discharging is high, a single phase cannot be obtained, and a phase with a low capacity appears. The most desirable value of z that can sufficiently exhibit the effect of N and obtain a high capacity is in the range of 0.05 ≦ z ≦ 0.15.
[0036]
(4) Further, the battery and the positive electrode of the present invention have the general formula Li _w Mg _v Fe _x NzO ₂ (However, N represents at least one selected from Ni, Co, Mn, Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B, w, v, x, z represents a number of 0 ≦ w ≦ 1.2, 0.001 ≦ v <0.02, 0.5 ≦ x <0.85, and 0 ≦ z ≦ 0.5). It is characterized by using. Preferably, w, v, x, and z are 0.2 ≦ w ≦ 1.15, 0.002 ≦ v ≦ 0.015, 0.7 ≦ x <0.85, 0.01 ≦ z ≦ 0.15, respectively. More preferably, w, v, x, and z are 0.2 ≦ w ≦ 1.05, 0.008 ≦ v ≦ 0.012, 0.75 ≦ x ≦ 0.82, 0.05, respectively. It is the range of ≦ z ≦ 0.15.
[0037]
Since the novel positive electrode active material of the present invention has Mg at the position of Li, w should not be able to take a value of 1 or more, but actually Li is lithium carbonate, lithium oxide, By-products such as lithium hydroxide are easily formed, and as a result, the amount of Li determined by chemical analysis may take a value larger than 1. However, these excess Lis only cover the positive electrode active material, and LiMeO ₂ It is not incorporated in the structure, and has a structure in which Mg is present at the Li position.
[0038]
The novel positive electrode active material of the present invention has the general formula Li _w Mg _v Fe _x N _z O ₂ The value of w representing the amount of Li varies depending on the state of charge and discharge, and the range is 0 ≦ w ≦ 1.2, preferably 0.2 ≦ w ≦ 1.15. More preferably, the range is 0.2 ≦ w ≦ 1.05. That is, Li ion deintercalation occurs due to charging and the value of w decreases, and Li ion intercalation occurs due to discharge and the value of w increases. If the amount of Li is greater than 1.2, the amount of by-products such as lithium carbonate, lithium oxide, and lithium hydroxide produced during the firing process will increase so much that these materials are used in the production of electrodes. The electrode cannot be successfully produced by reacting with the agent. In order to successfully produce an electrode, the smaller the amount of by-products, the better. The value of w is 1.2 or less, desirably 1.15 or less, and more desirably 1.05 or less.
[0039]
Further, the value of v representing the amount of Mg does not fluctuate due to charging and discharging, but is in the range of 0.001 ≦ v <0.02, and preferably in the range of 0.002 ≦ v ≦ 0.015. More desirably, the range is 0.008 ≦ v ≦ 0.012. When the value of v is less than 0.001, the effect of Mg is not sufficiently exhibited, the cycleability in deep charge and deep discharge is poor, and the capacity is also unfavorable. On the other hand, when the value of v exceeds 0.02, a single phase cannot be obtained, and a low-capacity phase appears. The most desirable value of v that can sufficiently exhibit the effect of Mg and obtain a high capacity is in the range of 0.008 ≦ v ≦ 0.012.
[0040]
The value of x representing the amount of Fe is in the range of 0.5 ≦ x <0.85, preferably in the range of 0.7 ≦ x <0.85, and more preferably in the range of 0.75 ≦ x ≦ 0. .82 range. When the value of x is less than 0.5, the capacity is remarkably lowered, which is not preferable. Moreover, when the value of x is 0.85 or more, the cycle characteristics in deep charge and deep discharge are poor, which is not preferable. The most desirable value of x that provides high capacity and good cycle performance in deep charge and deep discharge is in the range of 0.75 ≦ x ≦ 0.82.
[0041]
N is at least one selected from Ni, Co, Mn, Si, Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and B, preferably Ni, Co, Mn, Si, At least one selected from Al, Ca, Cu, Sn, P, In, and B, and more preferably at least one selected from Ni, Co, Mn, Si, Al, P, In, and B Most preferably, it is at least one selected from Si, Al, P, and B. The value of z does not vary depending on the state of charge and discharge, and the range is 0 ≦ z ≦ 0.5, preferably 0.01 ≦ z ≦ 0.15, and more preferably 0.05 ≦ z. The range is z ≦ 0.15. If the value of z exceeds 0.5, the overvoltage at the time of charging / discharging is high, a single phase cannot be obtained, and a phase with a low capacity appears. The most desirable value of z that can sufficiently exhibit the effect of N and obtain a high capacity is in the range of 0.05 ≦ z ≦ 0.15.
[0042]
Examples of the electrolyte include propylene carbonate, propylene carbonate derivatives, ethylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide. 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, gisanmethyl, methyl acetate, methyl propionate, ethyl propionate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, diethyl ether, 1,3- Propane sultone, sulfolane, 3-methyl-2-oxazolidine, tetrahydrofuran, tetrahydrofuran Body, dioxolane, 1,2-diethoxyethane, also at least one non-aqueous solvent and a lithium salt selected from the group consisting of a these halides, such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, LiBr, LiI, a mixed solution with at least one salt selected from the group consisting of lithium, a lower aliphatic carboxylate, lithium chloroborane, lithium tetraphenylborate, etc., and these mixed solutions and polymers, For example, by using a gel electrolyte mixed with at least one selected from the group consisting of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride, polymethyl methacrylate, and hexafluoropropylene, the positive electrode of the present invention is excellent. Show properties.
[0043]
By using a substance capable of reversibly occluding and releasing alkali metal ions for the negative electrode, the positive electrode of the present invention exhibits good characteristics. Among substances that can reversibly occlude and release alkali metal ions, graphite, pyrolytic graphite, carbon fiber, vapor-grown carbonaceous material, pitch-based carbonaceous material, coke-based carbonaceous material, phenol-based carbonaceous material, rayon Carbonaceous material, polyacrylonitrile carbonaceous material, needle coke, polyacrylonitrile carbon fiber, glassy carbon, carbon black, furfuryl alcohol carbonaceous material, polyparaphenylene, etc. At least one carbon material selected from the group consisting of at least one of low crystalline carbon and high crystalline carbon, or a combination of a plurality of these carbon materials, and these carbon materials include periodic tables IIIb and IVb. , Oxides containing chalcogen atoms or chalcogen compounds, and amorphous materials thereof At least one composite material selected from the group consisting of materials coated or fused with, conductive polymer materials such as polyacene, polyparaphenylene, polyaniline, polyacetylene, disulfide compounds, Li _x Fe ₂ O ₃ , Li _x Fe ₃ O ₄ , Li _x WO ₂ , Periodic table IIIb, IVb, oxides containing group Vb atoms, chalcogen compounds, and amorphous materials thereof are preferable.
[0044]
The use of the reversibly chargeable / dischargeable battery of the present invention is not particularly limited. For example, a notebook personal computer, pen input personal computer, pocket personal computer, notebook word processor, pocket word processor, electronic book player, mobile phone, cordless phone , Pager, handy terminal, portable copy, electronic notebook, calculator, LCD TV, electric shaver, electric tool, electronic translator, car phone, transceiver, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, Power supplies for portable printers, handy cleaners, portable CDs, video movies, navigation systems, refrigerators, air conditioners, TVs, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, game machines, lighting Equipment, toys, roadco Conditioners, medical equipment, automobiles, electric automobiles, golf carts, electric carts, can be used as a power source such as a power storage system. It can also be used for civilian use, military use, and space use.
[0045]
By using the positive electrode active material of the present invention, high battery capacity, long life, reduction of overvoltage during charge / discharge, rate characteristics, self-discharge characteristics, high temperature characteristics, high safety, etc. Improve performance. Further, by using the electrode of the present invention and a battery using the electrode in various systems, the system can be made compact and light. In addition, it can be applied to a system that requires charging and discharging at a high rate.
[0046]
The operation of the present invention will be specifically described. Since the positive electrode active material of the present invention has a layered structure or a zigzag layered structure in which lithium can be easily inserted and extracted, it exhibits excellent characteristics for charging and discharging at a large current. Furthermore, the positive electrode active material of the present invention has a structure in which Mg is substituted at the Li position. Since Li is monovalent, when divalent Mg is substituted at the position of Li, a vacancy of Li is generated, and electrons attracted from O enter there, and holes are introduced into O. Since electrons can be easily transferred using these holes, the positive electrode active material of the present invention has a characteristic that electron conductivity is superior to that of conventional materials. These can be confirmed also from the measurement of the Hall effect, and since the Hall coefficient shows a value as high as Si, it is proved that the material is highly conductive.
[0047]
The electronic conductivity of the positive electrode active material of the present invention is 10 to 100 times larger than that of a conventional positive electrode active material, and in some cases, exhibits a metallic behavior in which the electronic conductivity increases at low temperatures.
[0048]
Since the positive electrode active material of the present invention has a structure in which Mg is substituted at the position of Li, since Mg does not desorb in the Li layer even after Li is desorbed at the time of charging, this becomes a pillar and is large. No structural change or lattice volume change (pillar effect). LiMeO ₂ Li is desorbed by an amount 1/2 that of Li _0.5 MeO ₂ Up to this point, the electron density between the O layer and the O layer sandwiching the Li layer increases as Li is desorbed, so that the repulsive force causes expansion. Li _0.5 MeO ₂ When Li is further desorbed, the amount of tetravalent Me having a higher charge density than the amount of trivalent Me is increased, and the Me layer and the O layer are attracted and contracted in the opposite direction. LiMeO with layered or zigzag layered structure ₂ Then, these expansion and contraction mainly appear in the change of the c-axis lattice constant. Moreover, these occur at the time of charging when Li is desorbed, and follow a completely opposite change at the time of discharging when Li is inserted. If this expansion and contraction are repeated each time charging / discharging, the lattice collapses and the lifetime is reached. Since the conventional positive electrode active material has a high expansion coefficient and shrinkage ratio, the stress on the lattice is large and the cycle life is short.
[0049]
In the positive electrode active material of the present invention, by replacing Mg at the position of Li, holes introduced into O reduce the electron density between the O layer and the O layer sandwiching the Li layer, thereby reducing the O layer and the O layer. The repulsive force between the layers can be suppressed. Thereby, the expansion accompanying the desorption of Li is suppressed. Furthermore, since the holes introduced into the O decrease the electron density of the O layer, the attractive force between the Me layer and the O layer in which the tetravalent Me having a high charge density is increased can be suppressed. As a result, Li _0.5 MeO ₂ Shrinkage when Li is desorbed from is greatly suppressed.
[0050]
In the positive electrode active material of the present invention, the change from expansion to contraction during charging appears only in the c-axis lattice constant, and the change in lattice volume is extremely small. Therefore, the stress of the lattice is remarkably suppressed, and the lifetime is greatly extended.
[0051]
Since the positive electrode active material of the present invention stabilizes the crystal structure by substituting Mg at the Li position, it is possible to prevent Li from being desorbed due to moisture absorption and Me from being mixed into the Li position. This makes it possible to obtain a stable synthetic material and electrode performance regardless of the humidity level in the handling environment during firing or electrode fabrication. Also,
Since Mg acts as a sintering inhibitor, it is possible to suppress the coarsening of crystal grains. When coarse crystal grains are formed, the structural stress due to expansion and contraction at the time of charging cannot be relieved, so that the crystal grains are easily cracked and have a short life. The substitution of Mg can suppress the formation of such coarse particles.
[0052]
Furthermore, since Mn, Co, and Fe are less likely to oxidize than Ni, the life can be extended by these pillar effects. Since Mg, Mo, Cu, Al, Cs, and Si have the effect of increasing the electrical conductivity of the positive electrode active material, it is possible to reduce the overvoltage during charging and discharging.
[0053]
Further, since the ion radius of B, P and Si is small, the lattice volume of the positive electrode active material can be contracted by these substitutions, and the lifetime can be extended by suppressing the collapse due to the expansion of the lattice volume at the time of charging. Ca, Y, Nb, Al, Mg, B, and Si have low oxygen releasing ability and exist stably as oxides, so that they are excellent in high temperature characteristics and can improve stability. Further, substitution with Si, In, Sn, Mg, Ca, Bi is liable to cause defects in the crystal, so that the capacity can be increased and the rate characteristics can be improved.
[0054]
DETAILED DESCRIPTION OF THE INVENTION
(Comparative Example 1)
LiOH, Ni (OH) as raw material for positive electrode material ₂ Ni co-precipitated with 10 atomic% Co _0.9 Co _0.1 (OH) ₂ LiNi _0.9 Co _0.1 O ₂ These were prepared for 15 hours at room temperature using a ball mill in an Ar atmosphere. This was held at 150 ° C. for 1 h in an oxygen atmosphere, further held at 470 ° C. for 2 h, and then fired at 720 ° C. for 50 h to obtain a positive electrode material. For measurement of X-ray diffraction, a rotating counter-cathode sample horizontal X-ray diffractometer (RINT2000, manufactured by Rigaku Corporation) with an airtight chamber was used. The sample was attached to a glass holder in an Ar glove box and the surface was covered with mylar film to avoid contact with air. This was set in an airtight chamber provided with a Be window, and measured while minimizing the influence of moisture in the air while flowing He gas. Using a tube current of 250 mA, a tube voltage of 50 kV, and a CuKα radiation source, 2θ is 15 to 90 deg. Of step width 0.01 deg. , Measured by step scan with a measurement time of 0.5 sec. In order to increase the measurement accuracy of 2θ, the z-axis was positioned for each sample before measurement. In order to obtain the lattice constant with high accuracy, the measured lattice constant and cos ² The function with θ was approximated using the method of least squares, and a precise lattice constant was obtained. From the measurement result of X-ray diffraction, the obtained positive electrode material is hexagonal and α-NaFeO. ₂ The mold was confirmed to have a layered structure. FIG. 1 shows the a-axis lattice constant, the c-axis lattice constant, and the lattice volume.
[0055]
(Comparative Example 2)
LiOH, Ni (OH) as raw material for positive electrode material ₂ Ni co-precipitated with 10 atomic% Co and 1 atomic% Mg _0.9 Co _0.1 Mg _0.01 (OH) ₂ Using LiNi _0.89 Co _0.1 Mg _0.01 O ₂ These were prepared for 15 hours at room temperature using a ball mill in an Ar atmosphere. This was held at 150 ° C. for 1 h in an oxygen atmosphere, further held at 470 ° C. for 2 h, and then fired at 720 ° C. for 50 h to obtain a positive electrode material. For measurement of X-ray diffraction, a rotating counter-cathode sample horizontal X-ray diffractometer (RINT2000, manufactured by Rigaku Corporation) with an airtight chamber was used. The sample was attached to a glass holder in an Ar glove box and the surface was covered with mylar film to avoid contact with air. This was set in an airtight chamber provided with a Be window, and measured while minimizing the influence of moisture in the air while flowing He gas. Using a tube current of 250 mA, a tube voltage of 50 kV, and a CuKα radiation source, 2θ is 15 to 90 deg. Of step width 0.01 deg. , Measured by step scan with a measurement time of 0.5 sec. In order to increase the measurement accuracy of 2θ, the z-axis was positioned for each sample before measurement. In order to obtain the lattice constant with high accuracy, the measured lattice constant and cos ² The function with θ was approximated using the method of least squares, and a precise lattice constant was obtained. From the measurement result of X-ray diffraction, the obtained positive electrode material is hexagonal and α-NaFeO. ₂ The mold was confirmed to have a layered structure. FIG. 1 shows the a-axis lattice constant, the c-axis lattice constant, and the lattice volume. Since all of the a-axis lattice constant, the c-axis lattice constant, and the lattice volume are larger than those of Comparative Example 1, Mg is substituted at the Ni position.
[0056]
(Example 1)
LiOH, Ni (OH) as raw material for positive electrode material ₂ Ni co-precipitated with 10 atomic% Co _0.9 Co _0.1 (OH) ₂ And Mg (NO) ₃ Using LiNi _0.9 Co _0.1 Mg _0.01 O ₂ These were prepared for 15 hours at room temperature using a ball mill in an Ar atmosphere. This was held at 150 ° C. for 1 h in an oxygen atmosphere, further held at 470 ° C. for 2 h, and then fired at 720 ° C. for 50 h to obtain a positive electrode material. For measurement of X-ray diffraction, a rotating counter-cathode sample horizontal X-ray diffractometer (RINT2000, manufactured by Rigaku Corporation) with an airtight chamber was used. The sample was attached to a glass holder in an Ar glove box and the surface was covered with mylar film to avoid contact with air. This was set in an airtight chamber provided with a Be window, and measured while minimizing the influence of moisture in the air while flowing He gas. Using a tube current of 250 mA, a tube voltage of 50 kV, and a CuKα radiation source, 2θ is 15 to 90 deg. Of step width 0.01 deg. , Measured by step scan with a measurement time of 0.5 sec. In order to increase the measurement accuracy of 2θ, the z-axis was positioned for each sample before measurement. In order to obtain the lattice constant with high accuracy, the measured lattice constant and cos ² The function with θ was approximated using the method of least squares, and a precise lattice constant was obtained. From the measurement result of X-ray diffraction, the obtained positive electrode material is hexagonal and α-NaFeO. ₂ The mold was confirmed to have a layered structure. FIG. 1 shows the a-axis lattice constant, the c-axis lattice constant, and the lattice volume. Since all of the a-axis lattice constant, the c-axis lattice constant, and the lattice volume are larger than those of Comparative Examples 1 and 2, Mg is substituted at the Li position.
[0057]
(Example 2)
LiOH, Ni (OH) as raw material for positive electrode material ₂ Ni co-precipitated with 10 atomic% Co _0.9 Co _0.1 (OH) ₂ , And Mg (SH) ₄ Using LiNi _0.9 Co _0.1 Mg _0.01 O ₂ These were prepared for 15 hours at room temperature using a ball mill in an Ar atmosphere. This was held at 150 ° C. for 1 h in an oxygen atmosphere, further held at 470 ° C. for 2 h, and then fired at 720 ° C. for 50 h to obtain a positive electrode material. For measurement of X-ray diffraction, a rotating counter-cathode sample horizontal X-ray diffractometer (RINT2000, manufactured by Rigaku Corporation) with an airtight chamber was used. The sample was attached to a glass holder in an Ar glove box and the surface was covered with mylar film to avoid contact with air. This was set in an airtight chamber provided with a Be window, and measured while minimizing the influence of moisture in the air while flowing He gas. Using a tube current of 250 mA, a tube voltage of 50 kV, and a CuKα radiation source, 2θ is 15 to 90 deg. Of step width 0.01 deg. , Measured by step scan with a measurement time of 0.5 sec. In order to increase the measurement accuracy of 2θ, the z-axis was positioned for each sample before measurement. In order to obtain the lattice constant with high accuracy, the measured lattice constant and cos ² The function with θ was approximated using the method of least squares, and a precise lattice constant was obtained. From the measurement result of X-ray diffraction, the obtained positive electrode material is hexagonal and α-NaFeO. ₂ The mold was confirmed to have a layered structure. Since substantially the same a-axis lattice constant, c-axis lattice constant, and lattice volume as in Example 1 were obtained, Mg was substituted at the Li position.
[0058]
(Comparative Example 3)
Using the cell shown in FIG. 2, the electron conductivity was measured as follows. 3. In order to avoid the influence of moisture in the air, a material of Comparative Examples 1 and 2 as a positive electrode active material and polyvinylidene fluoride powder as a binder are mixed at a weight ratio of 93: 7 in a dry room of 3% humidity. 7ton / cm ² Was pressed into a disk shape having a diameter of 15 mm and a thickness of 0.35 mm. Pt-Pd was vapor-deposited on both sides of this disk using an ion sputtering apparatus (E-1030 type, manufactured by Hitachi). The Ar gas pressure is 0.02 to 0.04 torr, the discharge current is 20 mA, and the discharge time is 15 minutes on one side. Unnecessary vapor deposition part adhering to the side surface of the disk was removed using emery paper to form a positive electrode pellet 23, and then Ag paste 22 was applied to both sides of the disk, and electrolytic Cu foil having a thickness of 33 microns was further formed as a terminal 21. 0.5 ton / cm sandwiched between stainless steel plates 24 that are overlapped and covered with an insulating film 25 of polyethylene film ² The pressure of was applied and screwed. This was wrapped in a laminate film 26 covered with aluminum foil with a polyethylene film and thermocompression bonded to ensure airtightness. The measurement temperature was in the range of 50 ° C. to liquid nitrogen temperature (−196 ° C.), and the 1 kHz AC resistance after being allowed to stand for 1 hour was measured so that the temperature inside the active material was uniform. FIG. 3 shows the temperature dependence of the electronic conductivity. The electron conductivity is lower at the lower temperature side and as low as 0.02 to 0.1 S / m at -40 ° C. Further, although the rate of change δσ / δT of the electron conductivity σ with respect to the temperature T is not shown in the graph, it is positive in the temperature range of 50 ° C. to −196 ° C. Is also positive.
[0059]
(Example 3)
Using the cell shown in FIG. 2, the electron conductivity was measured as follows. In order to avoid the influence of moisture in the air, the material of Example 1 as a positive electrode active material and polyvinylidene fluoride powder as a binder were mixed at a weight ratio of 93: 7 in a dry room with a humidity of 3%. cm ² Was pressed into a disk shape having a diameter of 15 mm and a thickness of 0.35 mm. Pt-Pd was vapor-deposited on both sides of this disk using an ion sputtering apparatus (E-1030 type, manufactured by Hitachi). The Ar gas pressure is 0.02 to 0.04 torr, the discharge current is 20 mA, and the discharge time is 15 minutes on one side. Unnecessary vapor deposition part adhering to the side surface of the disk was removed using emery paper to form a positive electrode pellet 23, and then Ag paste 22 was applied to both sides of the disk, and electrolytic Cu foil having a thickness of 33 microns was further formed as a terminal 21. 0.5 ton / cm sandwiched between stainless steel plates 24 that are overlapped and covered with an insulating film 25 of polyethylene film ² The pressure of was applied and screwed. This was wrapped in a laminate film 26 covered with aluminum foil with a polyethylene film and thermocompression bonded to ensure airtightness. The measurement temperature was in the range of 50 ° C. to liquid nitrogen temperature (−196 ° C.), and the 1 kHz AC resistance after standing for 1 hour was measured so that the temperature inside the active material was uniform. FIG. 3 shows the temperature dependence of the electronic conductivity. The electron conductivity is higher at the lower temperature side and as high as 1000 S / m or higher at -40 ° C. Further, the rate of change δσ / δT of the electron conductivity σ with respect to the temperature T is negative in the temperature range of 50 ° C. to −196 ° C. and negative in the temperature range of 40 ° C. to −20 ° C.
[0060]
(Example 4)
The material of Example 1 was used as a positive electrode active material, and a binder and a conductive agent were mixed at a weight ratio of 85: 5: 10, and the resultant mixture was applied to a hardened aluminum foil having a thickness of 20 μm. did. Conductive agent has a specific surface area of 270m ² / G of artificial graphite was used. Polyvinylidene fluoride was used as a binder, and a solution obtained by dissolving PVDF in N-methyl-2-pyrrolidone (NMP) was added to the mixture of the positive electrode active material and the conductive agent. The coated electrode was dried at 80 ° C. for 2 hours to volatilize NMP, and then 1.5 ton / cm. ² And dried at 120 ° C. for 16 hours in a vacuum. The electrode area is 1.0 cm × 1.0 cm 2, and the mixture density is 2.8 to 3.1 g / cm. ³ The active material weight at this time is about 20 mg.
[0061]
The charge / discharge test was carried out by installing a cell screwed from both sides with a stainless steel plate 45 in the configuration shown in FIG. The cell is a stainless steel plate (SUS304) 45, a separator (polyethylene microporous film) 41, a counter electrode (Li metal) 46, a separator 41, a reference electrode (Li metal) 43 in an Ar glove box having a dew point of −67 ° C. or less. The separator 41, the positive electrode 44, the separator 41, and the stainless steel plate 45 were laminated in this order and screwed, and then the terminal 48 was connected and housed in the glass container 47. The separator 41 and the positive electrode 44 were sufficiently impregnated with the electrolytic solution 42 in advance. As the electrolytic solution 42, a mixed solvent of lithium hexafluorophosphate and ethylene carbonate and dimethyl carbonate having a volume ratio of 1: 2 is used. ₆ What was prepared so that the density | concentration of 1M might become a 1M solution was used. Current density 0.55mA / cm ² The positive electrode active material is charged to a constant capacity (50, 100, 150, 200, 220, 250 mAh / g, 274 mAh / g) with respect to 1 g of the positive electrode active material. -X-ray diffraction was measured using 10 minutes of washing in dimethoxyethane followed by air drying. FIG. 5 shows changes in the c-axis lattice constant, and FIG. 6 shows changes in the c-axis lattice constant (c / a) with respect to the a-axis lattice constant.
[0062]
On the other hand, the material of Example 1 was used as the positive electrode material, and the polyvinylidene fluoride was weighed in a weight ratio of 88: 7: 5 using graphite as a conductive agent, and kneaded for 30 minutes with a cracking machine. It apply | coated on both surfaces of the 20-micrometer-thick aluminum foil.
[0063]
Using a mixture prepared by preparing 93% by weight of artificial graphite as a negative electrode material and 7% by weight of polyvinylidene fluoride as a binder, it was applied to both surfaces of a copper foil having a thickness of 30 μm. The positive and negative electrodes were rolled and formed with a press machine, the terminals were spot welded, and then vacuum dried at 150 ° C. for 5 hours. FIG. 7 shows an example of a battery structure according to this example. A positive electrode 72 and a negative electrode 73 were laminated via a microporous polypropylene separator 71, wound in a spiral shape, and inserted into an aluminum battery can 74. Insulating films (insulators) 78 are provided on the upper and lower sides of the battery can 74 so that the respective electrodes do not contact the battery can 74 or the battery inner lid 75 to cause a short circuit. The negative terminal 76 was welded to the battery can 74, and the positive terminal 77 was welded to the battery inner lid 75. In addition, a safety valve (current cutoff valve) 79 is connected to the battery inner lid 75, and the safety valve (current cutoff valve) 79 is deformed by an increase in internal pressure of 10 atmospheres or more, so that the electrical contact between them is cut off. . The electrolyte contains 1 mol LiPF ₆ Was dissolved in 1 liter of a mixed solution of ethylene carbonate and diethyl carbonate and poured into the battery can 74. A battery lid was attached to the battery can to produce a cylindrical battery having a diameter of 14 mm and a height of 50 mm and a capacity of 1400 mAh. The battery is charged at a constant current of up to 4.2V at 1400mA, charged at a constant voltage of 4.2V for 3 hours, repeatedly discharged and discharged to 2.7V at 1400mA several times, charged to 4.2V at 1400mA, Taking this as a state where 100% of the battery capacity was charged, the positive electrode was taken out, washed in 1,2-dimethoxyethane for 10 minutes, and the amount of Li was determined by emission spectral analysis (ICP). Further, the battery was discharged at 1400 mA to 2.7 V, and 100% of the battery capacity was discharged. The positive electrode was taken out, washed in 1,2-dimethoxyethane for 10 minutes, and then subjected to Li spectroscopy by emission spectroscopy (ICP). The amount was determined. Thus, when the battery operating region was confirmed, Li was 0.87 mol (0.12 mol for Li desorption amount X) to 0.19 (0.80 for Li desorption amount X) with respect to 1 mol of Me. Mol).
[0064]
From FIG. 5, the maximum value c1 of the c-axis lattice constant from the state in which 100% of the battery capacity is charged to the state in which 100% of the battery capacity is discharged. _max And the minimum value c1 _min Rate of change (c1 _max -C1 _min ) / C1 _min Is as small as 0.02. Li _0.5 MeO ₂ Maximum value of c-axis lattice constant of c2 _max And Li _0.2 MeO ₂ C2 lattice constant c2 _min Rate of change with (c2 _max -C2 _min ) / C2 _min Is as small as 0.01. From FIG. 6, Li _0.5 MeO ₂ The maximum value of the ratio of the c-axis lattice constant c1 to the a-axis lattice constant a1 (c1 / a1) _max And Li _0.2 MeO ₂ Minimum value of the ratio of the c-axis lattice constant c2 to the a-axis lattice constant a2 (c2 / a2) _min And the difference is within the range of 0.1.
[0065]
(Comparative Example 4)
Using the materials of Comparative Examples 1 and 2 as the positive electrode active material, X-ray diffraction was measured in the same manner as in Example 4. FIG. 8 shows the change of the c-axis lattice constant when the material of Comparative Example 1 is used, and FIG. 9 shows the change of the c-axis lattice constant (c / a) with respect to the a-axis lattice constant. FIG. 10 shows the change of the c-axis lattice constant when the material of Comparative Example 2 is used, and FIG. 11 shows the change of the c-axis lattice constant (c / a) with respect to the a-axis lattice constant.
[0066]
On the other hand, the materials of Comparative Examples 1 and 2 were used as the positive electrode material, and the polyvinylidene fluoride was weighed in a weight ratio of 88: 7: 5 using graphite as a conductive agent and kneaded for 30 minutes with a large machine. Then, it apply | coated on both surfaces of the 20-micrometer-thick aluminum foil.
[0067]
Using a mixture prepared by preparing 93% by weight of artificial graphite as a negative electrode material and 7% by weight of polyvinylidene fluoride as a binder, it was applied to both surfaces of a copper foil having a thickness of 30 μm. The positive and negative electrodes were rolled and formed with a press machine, the terminals were spot welded, and then vacuum dried at 150 ° C. for 5 hours. In the same manner as in Example 4, a positive electrode 72 and a negative electrode 73 were laminated via a microporous polypropylene separator 71, wound in a spiral shape, and inserted into an aluminum battery can 74. The negative electrode terminal 76 was welded to the battery can 74 and the positive electrode terminal 77 was welded to the battery inner lid 75. The electrolyte contains 1 mol LiPF ₆ Was dissolved in 1 liter of a mixed solution of ethylene carbonate and diethyl carbonate and poured into the battery can 74. A battery lid was attached to the battery can to produce a cylindrical battery having a diameter of 14 mm and a height of 50 mm, which was the same as in Example 4, and having a capacity of 1400 mAh. The battery is charged at a constant current of up to 4.2V at 1400mA, charged at a constant voltage of 4.2V for 3 hours, repeatedly discharged and discharged to 2.7V at 1400mA several times, charged to 4.2V at 1400mA, Taking this as a state where 100% of the battery capacity was charged, the positive electrode was taken out, washed in 1,2-dimethoxyethane for 10 minutes, and the amount of Li was determined by emission spectral analysis (ICP). Furthermore, the battery was discharged at 1400 mA to 2.7 V, and 100% of the battery capacity was discharged. The positive electrode was taken out, washed in 1,2-dimethoxyethane for 10 minutes, and then subjected to Li spectroscopy by emission spectroscopy (ICP). The amount was determined. As a result, when the battery operating region was confirmed, in the material of Comparative Example 1, Li was 0.89 mol (0.11 mol in Li desorption amount X) to 0.22 (Li desorption) with respect to Me1 mol. When the amount of Li is less than 0.30 mol (0.70 mol for Li desorption amount X) with respect to 1 mol of Me, the hexagonal crystal becomes two-phase. separated. In the material of Comparative Example 2, Li is in a range from 0.90 mol (0.10 mol for Li desorption amount X) to 0.23 (0.77 mol for Li desorption amount X) with respect to 1 mol of Me. Met.
[0068]
8 and 10, the maximum value c1 of the c-axis lattice constant from the state in which 100% of the battery capacity is charged to the state in which 100% of the battery capacity is discharged. _max And the minimum value c1 _min Rate of change (c1 _max -C1 _min ) / C1 _min Is as large as 0.039 to 0.050. Li _0.5 MeO ₂ Maximum value of c-axis lattice constant of c2 _max And Li _0.2 MeO ₂ C2 lattice constant c2 _min Rate of change with (c2 _max -C2 _min ) / C2 _min Is as large as 0.040 to 0.058. From FIG. 9 and FIG. _0.5 MeO ₂ The maximum value of the ratio of the c-axis lattice constant c1 to the a-axis lattice constant a1 (c1 / a1) _max And Li _0.2 MeO ₂ Minimum value of the ratio of the c-axis lattice constant c2 to the a-axis lattice constant a2 (c2 / a2) _min The difference is also as large as 0.20 to 0.27.
[0069]
(Example 5)
A material having the composition shown in Table 1 to Table 8 is used as the positive electrode material, and graphite is used as the conductive agent and polyvinylidene fluoride is weighed to a weight ratio of 88: 7: 5, and 30 by a large machine. After partial kneading, it was applied to both sides of a 20 μm thick aluminum foil.
[0070]
Using a mixture prepared by preparing 93% by weight of artificial graphite as a negative electrode material and 7% by weight of polyvinylidene fluoride as a binder, it was applied to both surfaces of a copper foil having a thickness of 30 μm. The positive and negative electrodes were rolled and formed with a press machine, the terminals were spot welded, and then vacuum dried at 150 ° C. for 5 hours. In the same manner as in Example 4, a positive electrode 72 and a negative electrode 73 were laminated via a microporous polypropylene separator 71, wound in a spiral shape, and inserted into an aluminum battery can 74. The negative terminal 76 was welded to the battery can 74, and the positive terminal 77 was welded to the battery inner lid 75. The electrolyte contains 1 mol LiPF ₆ Was dissolved in 1 liter of a mixed solution of ethylene carbonate and diethyl carbonate and poured into the battery can 74. A battery lid was attached to the battery can to produce a cylindrical battery having a diameter of 14 mm and a height of 50 mm, which was the same as in Example 4, and having a capacity of 1400 mAh. The battery was charged at a constant current of up to 4.2V at 1400mA, charged at a constant voltage of 4.2V for 3 hours, and charged and discharged 5 times at 1400mA to 2.7V. The discharge capacity for the fifth time is shown in Table 1. It was. The cycle life was obtained by examining the number of cycles when the capacity reached 70% when the discharge capacity at the fifth time was 100%, and is also shown in Table 1. In the rate characteristics, the charging condition is 1400 mA at a constant current up to 4.2 V, then the battery is charged at a constant voltage of 4.2 V for 3 hours, and the discharging condition is 0.2 C discharge at 280 mA to 2.7 V and 4200 mA. Each of the 3C discharges discharged to 2.7 V was performed, and the capacity ratio in 3C discharge was shown in Table 1 in%, assuming that the capacity in 0.2C discharge was 100%. In the overcharge test, Table 1 shows the percentage of batteries that ignite when charging is continued at a constant current of 2800 mA. In the nail penetration test, the percentage of batteries that ignite when a battery charged at a constant current of 4.2V at 1400mA and charged at a constant voltage of 4.2V for 3 hours was pierced through the battery at a speed of 5mm / sec. Table 1 shows.
[0071]
[Table 1]

[0072]
[Table 2]

[0073]
[Table 3]

[0074]
[Table 4]

[0075]
[Table 5]

[0076]
[Table 6]

[0077]
[Table 7]

[0078]
[Table 8]

[0079]
(Comparative Example 5)
As the positive electrode material, the material shown as Comparative Example 5 in the above table was used, and graphite was used as a conductive agent, and polyvinylidene fluoride was weighed in a weight ratio of 88: 7: 5, and 30 minutes by a large machine. After kneading, it was applied to both sides of a 20 μm thick aluminum foil. Using a mixture prepared by preparing 93% by weight of artificial graphite as a negative electrode material and 7% by weight of polyvinylidene fluoride as a binder, it was applied to both surfaces of a copper foil having a thickness of 30 μm.
[0080]
A battery was produced in the same manner as in Example 5. Capacity, life, rate characteristics, overcharge test and nail penetration test were evaluated. The results are shown in Table 2. There are extremely low characteristics compared to Example 5.
[0081]
【The invention's effect】
According to the present invention, it is possible to obtain characteristics that are excellent in part or all of battery characteristics such as higher capacity, longer life, rate characteristics, high temperature characteristics, and improved safety of the positive electrode material for secondary batteries. it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing changes in lattice volume and lattice constant.
FIG. 2 is a schematic view of an electron conductivity measurement cell.
FIG. 3 is a graph showing the temperature dependence of conductivity.
FIG. 4 is a schematic view of a charge / discharge test cell.
5 is a graph showing changes in c-axis lattice constant of Example 4 using the positive electrode material of Example 1. FIG.
6 is a graph showing changes in c-axis lattice constant / a-axis lattice constant ratio of Example 4 using the positive electrode material of Example 1. FIG.
FIG. 7 is a diagram showing an example of a battery structure.
8 is a graph showing a change in c-axis lattice constant of Comparative Example 4 using the positive electrode material of Comparative Example 1. FIG.
9 is a graph showing changes in c-axis lattice constant / a-axis lattice constant of Comparative Example 4 using the positive electrode material of Comparative Example 1. FIG.
10 is a graph showing a change in c-axis lattice constant of Comparative Example 4 using the positive electrode material of Comparative Example 2. FIG.
11 is a graph showing changes in the c-axis lattice constant / a-axis lattice constant ratio of Comparative Example 4 using the positive electrode material of Comparative Example 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 21 ... Terminal, 22 ... Ag paste, 23 ... Positive electrode pellet, 24 ... Stainless steel plate, 25 ... Polyethylene film, 26 ... Laminate film, 41, 71 ... Separator, 42 ... Electrolyte, 43 ... Reference electrode, 44, 72 ... Positive electrode 46 ... Counter electrode, 73 ... Negative electrode, 74 ... Battery can, 75 ... Battery inner lid, 76 ... Negative electrode terminal, 77 ... Positive electrode terminal, 78 ... Film, 79 ... Safety valve.

Claims (7)

LiMeO _{2 having a} layered structure or a zigzag layered structure as a positive electrode active material Formula _{Li w Mg v Ni x M y} N z O 2 ( where having, M is, MnCo, at least one selected from Fe, N is, Si, Al, Ca, Cu , P, In, Sn , Mo, Nb, Y, Bi, and B, w, v, x, y, and z are 0 ≦ w ≦ 1.2, 0.001 ≦ v ≦ 0.02, 0, respectively. 0.5 ≦ x <0.85, 0.05 ≦ y ≦ 0.5, and 0 ≦ z ≦ 0.2.) Using a composite oxide in which Mg is present at the Li position. A battery that includes a nonaqueous electrolyte and that can be reversibly charged and discharged a plurality of times. LiMeO _{2 having a} layered structure or a zigzag layered structure as a positive electrode active material The general formula _{Li w Mg v Co x N z} O 2 with (where, N is the, Ni, Mn, Fe, Si , Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, from B Represents at least one selected, and w, v, x, and z are 0 ≦ w ≦ 1.2, 0.001 ≦ v <0.02, 0.5 ≦ x <0.85, 0 ≦, respectively. z ≦ 0.5 is represented.) A battery capable of reversibly charging and discharging a plurality of times using a composite oxide in which Mg is present at the Li position represented by z) and having a nonaqueous electrolyte containing a lithium salt. LiMeO _{2 having a} layered structure or a zigzag layered structure as a positive electrode active material The general formula _{Li w Mg v Mn x N z} O 2 with (where, N is the, Ni, Co, Fe, Si , Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, from B Represents at least one selected, and w, v, x, and z are 0 ≦ w ≦ 1.2, 0.001 ≦ v <0.02, 0.5 ≦ x <0.85, and 0.0, respectively. 01 ≦ z ≦ 0.5.) A battery capable of being reversibly charged and discharged a plurality of times using a composite oxide in which Mg is present at the Li position represented by (1) and having a nonaqueous electrolyte containing a lithium salt. LiMeO _{2 having a} layered structure or a zigzag layered structure as a positive electrode active material The general formula _{Li w Mg v Fe x N z} O 2 with (where, N is the, Ni, Co, Mn, Si , Al, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, from B Represents at least one selected, and w, v, x, and z are 0 ≦ w ≦ 1.2, 0.001 ≦ v <0.02, 0.5 ≦ x <0.85, 0 ≦, respectively. z ≦ 0.5 is represented.) A battery capable of reversibly charging and discharging a plurality of times using a composite oxide in which Mg is present at the Li position represented by z) and having a nonaqueous electrolyte containing a lithium salt. As a positive electrode active material, Li, O, Mg is an essential element, it has a layered or zigzag layered LiMeO ₂ structure, Me contains at least one selected from Mn, Co, Ni, Fe, Li A composite oxide having Mg at a position is used, and the positive electrode active material has a maximum value c1 _max of c-axis lattice constant from a state where 100% of the battery capacity is charged to a state where 100% of the battery capacity is discharged. And a rechargeable battery having a non-aqueous electrolyte containing a lithium salt having a change rate ((c1 _max −c1 _min ) / c1 _min ) of 0.03 or less with respect to the minimum value c1 _min . As a positive electrode active material, Li, O, Mg is an essential element, it has a layered or zigzag layered LiMeO ₂ structure, Me contains at least one selected from Mn, Co, Ni, Fe, Li A composite oxide in which Mg is present at a position is used, and the positive electrode active material changes between the maximum value c2 _max of the c-axis lattice constant of Li _0.5 MeO ₂ and the minimum value c2 _min of the c-axis lattice constant of Li _0.2 MeO ₂ A battery having a non-aqueous electrolyte containing a lithium salt having a rate ((c2 _max −c2 _min ) / c2 _min ) of 0.01 or less and capable of being reversibly charged and discharged a plurality of times. As a positive electrode active material, Li, O, Mg is an essential element, it has a layered or zigzag layered LiMeO ₂ structure, Me contains at least one selected from Mn, Co, Ni, Fe, Li A composite oxide having Mg in the position is used, and the positive electrode active material has a maximum value ((c1 / a1) _max ) of the ratio of the c-axis lattice constant c1 to the a-axis lattice constant a1 of Li _0.5 MeO ₂ , and Li Reversible with a non-aqueous electrolyte containing a lithium salt whose difference from the minimum value of the c-axis lattice constant c2 to the a-axis lattice constant a2 of _0.2 MeO ₂ ((c2 / a2) _min ) is within 0.1 A battery that can be charged and discharged multiple times.

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