JP2009064702A - Active material for nonaqueous electrolyte secondary battery, its manufacturing method, and battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery excellent mainly in charge discharge cycle characteristics. <P>SOLUTION: The manufacturing method of the active material for a nonaqueous electrolyte secondary battery includes a process of heating a raw material containing manganese and nickel under an atmosphere with a pressure of oxygen gas of 10 MPa or more and 200 MPa or less, and the raw material contains at least a kind selected from a group consisting of a carbonate coprecipitation matter containing manganese and nickel, a hydroxide coprecipitation matter containing manganese and nickel, a mixture of nitrate containing manganese and nitrate containing nickel, and a mixture of organic acid salt containing manganese and organic acid salt containing nickel, and the active material for the nonaqueous electrolyte secondary battery made by the above manufacturing method is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to an improved manganese nickel composite oxide used as a positive electrode active material for a lithium secondary battery and a method for producing the same.

  With the rapid development of technology in the electronics field in recent years, electronic devices have become smaller and lighter, and electronic devices have become portable and cordless. Secondary batteries as power sources for such electronic devices are also eagerly desired to be smaller, lighter, and have higher energy density. As a secondary battery that meets such a demand, a nonaqueous electrolyte secondary battery having a high volumetric energy density can be cited.

  A non-aqueous electrolyte secondary battery is a battery using a non-aqueous electrolyte in which a lithium salt or the like is dissolved in an organic solvent. The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery has a higher voltage that is decomposed compared to the aqueous electrolyte used in, for example, a nickel-cadmium secondary battery, and the non-aqueous electrolyte secondary battery is an aqueous solution. High electromotive force can be obtained as compared with the secondary battery using the electrolyte. For this reason, the nonaqueous electrolyte secondary battery can achieve high energy density. Furthermore, in a non-aqueous electrolyte secondary battery, since a stable potential region of the non-aqueous electrolyte is wide, a wide range of substances can be selected as materials for the positive electrode and the negative electrode.

Recently, many small coin-type non-aqueous electrolyte secondary batteries have been developed, and such batteries are widely used for backup applications of electronic devices in addition to main power supply applications such as watches.
Conventionally, a silver oxide battery, which is a primary battery, has been mainly employed as a power source for a wristwatch. However, the usage period of this battery is about 3 years, and environmental pollution due to harmful substances contained in the silver oxide battery is also a problem. For this reason, the demand for secondary batteries is increasing. In particular, a coin-type non-aqueous electrolyte secondary battery used for a main power source is required to have not only a volume energy density but also good charge / discharge cycle characteristics because of its commercial characteristics.

  As a positive electrode active material of a non-aqueous electrolyte secondary battery, research and development have been conventionally conducted to apply manganese dioxide, which is expected to have a high capacity. Manganese dioxide consisting only of manganese and oxygen is known to have poor charge / discharge cycle characteristics, so attempts have been made to improve charge / discharge cycle characteristics by adding different metals other than manganese to manganese dioxide. .

For example, in Non-Patent Document 1 and Non-Patent Document 2, manganese dioxide of manganese dioxide is obtained by electrolytic synthesis from a mixed aqueous solution raw material in which a sulfate of aluminum, cobalt, or nickel is dissolved in an aqueous solution of manganese sulfate used as a synthetic raw material. A composite manganese oxide in which a part of is substituted with aluminum, cobalt or nickel has been synthesized. The crystal structure of the synthesized complex manganese oxide changes depending on conditions such as the temperature at the time of synthesis and the pH of the raw material solution. For example, α-phase manganese dioxide type, β-phase manganese dioxide type, or γ-phase manganese dioxide type A composite manganese oxide is obtained.
E. Macefaux, A.M. Verbaere and D.C. Guyomard, Journal of Power Sources 157 (2006) 443-447 E. Macefaux, A.M. Verbaere and D.C. Guyomard, Journal of Physics and Chemistry of Solid 67 (2006) 1315-1319

  However, the discharge capacity of the battery of Non-Patent Document 2 is halved after only 15 cycles. Therefore, the charge / discharge cycle characteristics of the battery of Non-Patent Document 2 are never practical.

  As described above, in the conventional technology, good charge / discharge cycle characteristics are not obtained in a nonaqueous electrolyte secondary battery using manganese dioxide or composite manganese oxide, which is expected to have a high capacity, as a positive electrode active material.

  A composite oxide obtained by adding a different metal to an oxide is generally obtained by a method in which an oxide and a compound of a different metal are mixed and heated to a high temperature. However, in the case of manganese dioxide, when it is heated to high temperature, oxygen is released and it decomposes, so that a composite oxide cannot be obtained by the above method.

  Non-Patent Document 1 and Non-Patent Document 2 succeed in obtaining a complex oxide by performing electrolysis at a temperature of 180 ° C. or lower. However, their charge / discharge cycle characteristics are not good.

  The present inventor has inferred that the cause of the low cycle characteristics in the prior art is electrolytic synthesis using an aqueous solution. Conventionally, manganese dioxide synthesized by electrolysis is said to incorporate water in an aqueous solution, OH groups or hydrogen derived from water, and composite oxidation synthesized in Non-Patent Document 1 and Non-Patent Document 2. It is possible that they are also included in the object. Moreover, the non-aqueous electrolyte secondary battery is a battery whose characteristics are deteriorated by mixing water or OH groups derived from water or hydrogen.

Therefore, as a result of intensive studies by the present inventors, when a compound of manganese and nickel is heated in an atmosphere of oxygen gas pressure higher than the oxygen gas partial pressure (0.02 MPa) at atmospheric pressure, manganese and nickel are contained. It has been found that a composite oxide can be obtained.
That is, this invention includes the process of heating the raw material containing manganese and nickel in the atmosphere whose pressure of oxygen gas is 10 MPa or more and 200 MPa or less, and the raw material containing manganese and nickel contains manganese and nickel. Group consisting of carbonate coprecipitate, hydroxide coprecipitate containing manganese and nickel, a mixture of nitrate containing manganese and nitrate containing nickel, and a mixture of organic acid salt containing manganese and organic acid salt containing nickel The manufacturing method of the active material for nonaqueous electrolyte secondary batteries containing at least 1 sort (s) selected from these.

  As described above, when manganese dioxide is heated in an atmosphere containing oxygen gas at the same pressure as the partial pressure of oxygen gas at atmospheric pressure, manganese dioxide releases oxygen and decomposes. However, the higher the pressure of the oxygen gas, the more the decomposition reaction that releases oxygen of manganese dioxide can be suppressed. Furthermore, in the production method of the present invention, since heating is performed without using water, the obtained composite oxide does not contain water, OH groups or hydrogen derived from water. For this reason, the effect by addition of a dissimilar metal element is exhibited, and it becomes possible to improve charging / discharging cycling characteristics.

Further, the present invention provides the following formula (1) produced by the above production method:
Mn _1-x Ni _x O _2-y (1)
(Wherein 0.01 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5)
The active material for nonaqueous electrolyte secondary batteries containing the manganese nickel complex oxide represented by these.

  In a preferred embodiment of the present invention, the manganese nickel composite oxide is 0.692 ± 0.005 nm, 0.490 ± 0.005 nm, 0.309 ± 0.005 nm, 0.240 on a powder X-ray diffraction chart. At least seven X-ray diffraction peaks corresponding to the interplanar spacing d of ± 0.005 nm, 0.183 ± 0.005 nm, 0.153 ± 0.005 nm, and 0.135 ± 0.005 nm are shown.

  In another preferred embodiment of the present invention, the manganese nickel composite oxide is 0.473 ± 0.005 nm, 0.244 ± 0.005 nm, 0.215 ± 0.005 nm, 0 in the powder X-ray diffraction chart. . At least 6 X-ray diffraction peaks corresponding to the interplanar spacing d of 167 ± 0.005 nm, 0.148 ± 0.005 nm, and 0.141 ± 0.005 nm are shown.

  In still another preferred embodiment of the present invention, the manganese nickel composite oxide has a γ phase manganese dioxide type crystal structure or a β phase manganese dioxide type crystal structure, or a γ phase manganese dioxide type and a β phase dioxide dioxide. Including mixed crystals with manganese type.

  The present invention also relates to a nonaqueous electrolyte secondary battery comprising a negative electrode, a positive electrode containing the active material for a nonaqueous electrolyte secondary battery, a separator disposed between the negative electrode and the positive electrode, and a nonaqueous electrolyte. .

  In the manufacturing method of the present invention, a raw material containing manganese and nickel is heated in an atmosphere containing oxygen gas at a high pressure of 0.1 MPa or more and 200 MPa or less without using water or an aqueous solution. For this reason, a composite oxide containing nickel and manganese is obtained by the manufacturing method of the present invention, and the obtained composite oxide does not contain OH groups or hydrogen derived from water. Therefore, by using such a manganese nickel composite oxide as an active material of a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery having good charge / discharge cycle characteristics can be obtained.

  The method for producing an active material for a non-aqueous electrolyte secondary battery of the present invention includes a step of heating a raw material containing manganese and nickel in an atmosphere having an oxygen gas pressure of 0.1 MPa to 200 MPa. The raw material containing manganese and nickel includes carbonate coprecipitate containing manganese and nickel, hydroxide coprecipitate containing manganese and nickel, a mixture of nitrate containing manganese and nitrate containing nickel, and manganese. It contains at least one selected from the group consisting of a mixture of an organic acid salt containing nickel and an organic acid salt containing nickel. By the production method of the present invention, a composite oxide containing manganese and nickel (manganese nickel composite oxide) is obtained.

  In the manufacturing method of the present invention, unlike electrolysis, it is not necessary to use water or an aqueous solution. For this reason, the manganese nickel composite oxide obtained by the production method of the present invention is hardly mixed with water or OH groups or hydrogen derived from water. Therefore, it is possible to suppress deterioration in charge / discharge cycle characteristics caused by mixing of water or OH groups derived from water or hydrogen. In other words, by using the manganese nickel composite oxide as an active material for a non-aqueous electrolyte secondary battery, the charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery can be compared with the conventional non-aqueous electrolyte secondary battery using manganese oxide. The charge / discharge cycle characteristics can be improved.

The raw material containing manganese and nickel is preferably in a state where manganese and nickel are mixed at an atomic level, as in the obtained manganese nickel composite oxide. Thereby, the synthesis reaction of manganese nickel complex oxide can be facilitated and the homogeneity of the produced nickel manganese complex oxide can be enhanced.
In addition, when a mixture obtained by mechanically mixing a manganese compound and a nickel compound is used as a raw material, a manganese nickel composite oxide having a heterogeneous composition is often obtained. A manganese nickel composite oxide having a non-homogeneous composition may not provide a sufficient effect of improving cycle characteristics due to the composite of nickel.

  As described above, the raw material containing manganese and nickel includes a carbonate coprecipitate containing manganese and nickel, a hydroxide coprecipitate containing manganese and nickel, a mixture of nitrate containing nickel and nitrate containing nickel, And a mixture of an organic acid salt containing manganese and an organic acid salt containing nickel.

  The carbonate coprecipitate containing manganese and nickel is, for example, a precipitate formed by mixing an aqueous solution containing manganese ions and nickel ions and an aqueous solution of an alkali carbonate (sodium carbonate, potassium carbonate, etc.) with stirring. Can be obtained by washing with water. Examples of the aqueous solution containing manganese ions and nickel ions include a mixed aqueous solution of manganese sulfate and nickel sulfate.

  A hydroxide coprecipitate containing manganese and nickel is produced, for example, by mixing an aqueous solution containing manganese ions and nickel ions with an aqueous solution of alkali hydroxide (sodium hydroxide, potassium hydroxide, etc.) while stirring. The obtained precipitate can be obtained by washing with water. Examples of the aqueous solution containing manganese ions and nickel ions include a mixed aqueous solution of manganese sulfate and nickel sulfate.

  A mixture of a manganese-containing nitrate and a nickel-containing nitrate in which manganese and nickel are mixed at an atomic level, and a mixture of an organic acid salt containing manganese and an organic acid salt containing nickel include, for example, the above-mentioned salt containing manganese An aqueous salt solution containing nickel can be prepared by spray drying. Examples of the organic acid salt include acetate.

  In addition, in the raw material containing nickel and manganese, it is preferable that the atomic ratio of nickel with respect to the sum total of nickel and manganese is 0.01-0.5.

According to the production method of the present invention, for example, the following formula (1):
Mn _1-x Ni _x O _2-y (1)
(Wherein 0.01 ≦ x ≦ 0.5 and 0 ≦ y ≦ 0.5)
A manganese nickel composite oxide represented by The manganese nickel composite oxide represented by the formula (1) has a discharge capacity higher than that of conventionally used manganese dioxide. Therefore, by using the manganese nickel composite oxide of the formula (1), not only the charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery but also the discharge capacity can be improved.

  In the manganese nickel composite oxide represented by the formula (1), the formal valence of manganese is tetravalent, and the formal valence of nickel is considered to be trivalent to tetravalent. In order to produce such a manganese-nickel composite oxide, it is necessary to heat a raw material containing manganese and nickel in an atmosphere in which the pressure of oxygen gas is equal to or higher than the partial pressure of oxygen gas at atmospheric pressure.

Conventionally known manganese nickel composite oxides (eg, NiMnO ₃ , Ni ₂ MnO _4, etc.) have a formal valence of manganese and nickel has a bivalence. Such conventionally known manganese-nickel composite oxides are synthesized under atmospheric pressure, that is, under the partial pressure of oxygen gas at atmospheric pressure.
Thus, in the heat synthesis under the pressure of oxygen gas at atmospheric pressure, the formalization number of nickel is divalent. In order to obtain a manganese-nickel composite oxide containing a trivalent or more expensive nickel, it is necessary to promote the oxidation of nickel in an atmosphere having a high oxygen gas pressure. As described above, in the present invention, since the partial pressure of oxygen gas in the atmosphere is high, the formal valence of nickel can be made trivalent to tetravalent.
Furthermore, by increasing the pressure of the oxygen gas contained in the heating atmosphere, manganese oxide can be prevented from being decomposed by releasing oxygen.

Specifically, in order to obtain the manganese-nickel composite oxide of the formula (1), the pressure of oxygen gas contained in the atmosphere for heating the raw material containing manganese and nickel needs to be 0.1 MPa or more. . By heating a raw material containing manganese and nickel in an atmosphere in which the pressure of oxygen gas is 0.1 MPa or more, it becomes easy to synthesize manganese oxide containing nickel having a high formal valence such as trivalent to tetravalent. Because. When the pressure of the oxygen gas is less than 0.1 MPa, the obtained manganese nickel composite oxide tends to contain the oxide Mn _1-x Ni _x O containing divalent nickel and having no discharge activity. When the obtained manganese nickel composite oxide contains an oxide having no discharge activity, the capacity of the manganese nickel composite oxide decreases.

  The upper limit of the pressure of oxygen gas is limited to the upper limit of the pressure resistance of the synthesis reaction vessel. In the present invention, manganese nickel composite oxide is not synthesized in an atmosphere in which the pressure of oxygen gas exceeds 200 MPa, but if a synthesis reaction vessel that can withstand higher pressure can be used, a more preferable result is obtained. It is thought that it is obtained.

  In the manganese nickel composite oxide of the formula (1), the amount of oxygen (2-y) can be controlled by adjusting the amount of Ni, the pressure of oxygen gas contained in the atmosphere, and the like.

  As a result of the study, in the manganese nickel composite oxide represented by the formula (1), when the atomic ratio x of nickel in the total of manganese and nickel exceeds 0.5, the y value may exceed 0.5. I understood. It was also found that when the atomic ratio x and y values exceed 0.5, no single-phase manganese nickel composite oxide was obtained, and the nickel nickel composite oxide contained nickel oxide (NiO) as an impurity. Since NiO does not participate in the charge / discharge reaction, the charge / discharge capacity decreases as the NiO content increases. Therefore, a manganese nickel composite oxide containing NiO is not preferable as an active material.

  The atomic ratio x of nickel in the total of manganese and nickel is preferably 0.01 to 0.5, and more preferably 0.2 to 0.5. If the atomic ratio x is 0.01 or more, the effect of improving the cycle characteristics can be obtained. Note that when the atomic ratio x exceeds 0.5, the capacity decreases.

By changing the kind of the raw material containing manganese and nickel, a manganese nickel composite oxide of the formula (1) having a different crystal structure can be obtained.
At present, roughly divided, manganese nickel composite oxides having the following crystal structures (i) to (iv) are obtained, and even when any of the crystal structure manganese nickel composite oxides is used, The effect is obtained.
(I) Manganese nickel composite oxide having a crystal structure of γ phase manganese dioxide type or β phase manganese dioxide type (ii) Manganese nickel composite oxide containing mixed crystals of γ phase manganese dioxide type and β phase manganese dioxide type ( iii) In the powder X-ray diffraction chart, 0.692 ± 0.005 nm, 0.490 ± 0.005 nm, 0.309 ± 0.005 nm, 0.240 ± 0.005 nm, 0.183 ± 0.005 nm, 0 In the manganese nickel composite oxide (iv) powder X-ray diffraction chart showing at least 7 X-ray diffraction peaks corresponding to the interplanar spacing d of 153 ± 0.005 nm and 0.135 ± 0.005 nm, 0.473 ± 0.005 nm, 0.244 ± 0.005 nm, 0.215 ± 0.005 nm, 0.167 ± 0.005 nm, 0.148 ± 0.005 nm, And a manganese nickel composite oxide exhibiting at least six X-ray diffraction peaks corresponding to an interplanar spacing d of 0.141 ± 0.005 nm

  The manganese nickel composite oxides (i) to (iv) can be obtained by selecting an appropriate raw material from the salt according to each crystal structure and heating the raw material at 200 to 600 ° C. Note that the preferred heating temperature differs somewhat depending on the crystal structure.

(I) Manganese nickel composite oxide As a raw material, a mixture of a nitrate containing manganese and a nitrate containing nickel is used, and the raw material is heated at 200 ° C. to 400 ° C., whereby crystals similar to β-phase manganese dioxide are obtained. A manganese nickel composite oxide having a structure can be obtained.
Using a mixture of acetate containing manganese and acetate containing nickel as a raw material, and heating the raw material at 200 ° C. to 400 ° C., manganese nickel composite oxidation having a crystal structure similar to that of γ phase manganese dioxide You can get things.

(Ii) Manganese nickel composite oxide As a raw material, a hydroxide coprecipitate containing manganese and nickel is used, and the raw material is heated at 200 ° C. to 400 ° C. A manganese nickel composite oxide containing a mixed crystal with the manganese type can be obtained.

(Iii) Manganese nickel composite oxide As a raw material, a carbonate coprecipitate containing manganese and nickel is used, and the raw material is heated at 200 ° C. to 400 ° C. to obtain 0.473 in a powder X-ray diffraction chart. With interplanar spacing d of ± 0.005 nm, 0.244 ± 0.005 nm, 0.215 ± 0.005 nm, 0.167 ± 0.005 nm, 0.148 ± 0.005 nm, and 0.141 ± 0.005 nm A manganese nickel composite oxide having a novel crystal structure showing at least six corresponding X-ray diffraction peaks is obtained.

(Iv) Manganese nickel composite oxide As a raw material, a carbonate coprecipitate containing manganese and nickel is used, and the raw material is heated at 400 to 600 ° C., whereby 0.692 ± 0.005 nm, 0.490 ± 0.005 nm, 0.309 ± 0.005 nm, 0.240 ± 0.005 nm, 0.183 ± 0.005 nm, 0.153 ± 0.005 nm, and 0.135 ± 0 A manganese nickel composite oxide having a novel crystal structure exhibiting at least seven X-ray diffraction peaks corresponding to an interplanar spacing d of 0.005 nm is obtained.

  The crystal structure of the manganese-nickel composite oxide (iii) is a tetragonal crystal structure having a lattice constant a of 0.487 nm and a lattice constant c of 1.420 nm. The crystal structure of the oxide is tetragonal and coincides with the crystal structure having a lattice constant a of 0.978 nm and a lattice constant c of 0.286 nm. However, at present, the crystal system and lattice constant of the two manganese nickel composite oxides cannot be stated.

  In heating any of the above raw materials, if the heating temperature is lower than 200 ° C., the raw material or a decomposition product of the raw material remains even if the heating time is 20 hours. Therefore, a mixture of the manganese nickel composite oxide and the raw material or the decomposition product of the raw material is obtained. When the mixture is used as an active material, since the raw material or the decomposition product of the raw material does not participate in the charge / discharge reaction, the charge / discharge capacity of the active material decreases as the content of the raw material or the decomposition product of the raw material in the mixture increases. End up. Therefore, a mixture of a manganese nickel composite oxide and a raw material or a decomposition product of the raw material is not preferable as an active material. Note that if the heating time is further longer than 20 hours, the synthesis reaction proceeds, and the raw material or the decomposition product of the raw material will eventually react with the manganese-nickel composite oxide. Since it increases, it is industrially unpreferable.

  In any case where any of the raw materials is heated, if the heating temperature is higher than 600 ° C., the manganese nickel composite oxide represented by the formula (1) decomposes by releasing oxygen, and does not function as an active material. Become.

  In the future, by changing the synthesis conditions, a manganese nickel composite oxide represented by the formula (1) and having a crystal structure other than (i) to (iv) may be obtained.

The manganese nickel composite oxide obtained by the production method of the present invention can be used as a positive electrode active material of a non-aqueous electrolyte secondary battery.
The nonaqueous electrolyte secondary battery includes, for example, a positive electrode including the manganese nickel composite oxide as a positive electrode active material, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte.

FIG. 1 shows a longitudinal sectional view of a nonaqueous electrolyte secondary battery (coin-type battery) according to an embodiment of the present invention.
The coin-type battery of FIG. 1 includes a pellet-shaped positive electrode 1, a pellet-shaped negative electrode 2, a separator 3 disposed between the positive electrode 1 and the negative electrode 2, and a non-transferring lithium ion between the positive electrode 1 and the negative electrode 2. A water electrolyte (not shown), a positive electrode case 6 that accommodates these, a sealing plate 5, and a gasket 4 are included. The battery of FIG. 1 is sealed by caulking the opening end of the positive electrode case 6 to the sealing plate 5 via the gasket 4.

The pellet-shaped positive electrode 1 includes, for example, the manganese nickel composite oxide, a conductive material, and a binder. Such a positive electrode 1 can be obtained, for example, by mixing the manganese nickel composite oxide, a conductive material, and a binder, and press-molding the obtained mixture.
As the conductive material added to the positive electrode, materials known in the art can be used. Examples of such a material include carbon black and graphite.
As the binder added to the positive electrode, a resin material known in the art can be used. Examples of such a resin material include polytetrafluoroethylene and polyvinylidene fluoride.

  The average particle diameter of the manganese nickel composite oxide, which is a positive electrode active material, is preferably 1 to 100 μm. When the average particle size is smaller than 1 μm, the density of the pellet-like positive electrode 1 is lowered, and the battery capacity may be reduced. If the average particle size is larger than 100 μm, the molding strength of the pellet-shaped positive electrode 1 may be reduced, and the yield during production may be reduced.

  The positive electrode active material contained in the nonaqueous electrolyte secondary battery of the present invention may contain other materials known in the art in addition to the manganese nickel composite oxide represented by the formula (1).

  Among the manganese nickel composite oxides having different crystal structures as described above, since a relatively high discharge capacity can be obtained, a manganese nickel composite oxide having a γ-phase manganese dioxide type crystal structure is preferable.

The pellet-shaped negative electrode 2 includes, for example, a negative electrode active material, a conductive material, and a binder. Such a negative electrode 2 can be obtained, for example, by mixing a negative electrode active material, a conductive material, and a binder, and pressure-molding the obtained mixture.
As the negative electrode active material, a lithium compound that is electrochemically known and capable of electrochemically inserting and extracting lithium can be used. Examples of such lithium compounds include lithium titanium composite oxides.
As the conductive material added to the negative electrode, materials known in the art can be used. Examples of such a material include carbon black and graphite.
As the binder added to the negative electrode, a resin material known in the art can be used. Examples of such a resin material include polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and polyacrylic acid.

  Or the negative electrode 2 may be comprised from the metal lithium or lithium alloy of predetermined thickness. The lithium alloy used preferably contains at least aluminum. The aluminum content in the lithium alloy is preferably 0.2 to 15 wt%.

The lithium alloy may be synthesized outside the battery or may be synthesized inside the battery. When a lithium alloy is synthesized outside the battery, lithium and an element other than lithium are previously alloyed. A battery is manufactured using the obtained alloy.
When a lithium alloy is synthesized in a battery, for example, lithium (or a metal other than lithium) is included in the negative electrode, and a metal foil (or lithium foil) made of an element other than lithium is formed on the surface of the negative electrode facing the positive electrode. A battery is manufactured by pressure bonding. Thereby, alloying with lithium and elements other than lithium can be advanced in a battery during or after battery assembly.

  The separator 3 allows lithium ions in the non-aqueous electrolyte to pass while preventing a short circuit between the positive electrode 1 and the negative electrode 2. As the separator 3, for example, a nonwoven fabric formed of a fibrous resin or a porous film made of a resin can be used. Examples of the resin constituting the separator include polypropylene and polyethylene.

The gasket 4 is provided so as to seal the gap in a gap generated between the positive electrode case 6 and the sealing plate 5 when the opening of the positive electrode case 6 is sealed with the sealing plate 5. As a result, the positive electrode 1, the negative electrode 2, the separator 3, and the nonaqueous electrolytic solution are accommodated in the internal space sealed by the positive electrode case 6, the sealing plate 5, and the gasket 4.
The gasket 4 has a function of insulating the positive electrode case 6 and the sealing plate 5 and preventing leakage of the nonaqueous electrolyte accommodated in the internal space surrounded by the positive electrode case 6 and the sealing plate 5. . Furthermore, the gasket 4 has a function of preventing moisture from entering the internal space.

  As a constituent material of the gasket 4, a material known in the art can be used. Examples of such a material include PFA resin (a copolymer resin of tetrafluoroethylene and perfluoroalkyl vinyl ether).

  The positive electrode case 6 is a container made of a conductive metal and having a shallow dish shape that accommodates the positive electrode 1. The positive electrode case 6 is in contact with the positive electrode 1 and becomes an external positive electrode terminal of the battery. Specifically, for the positive electrode case 6, for example, a metal container made of stainless steel or the like can be used. Further, the positive electrode case can be made of a material obtained by laminating a plurality of kinds of metals such as stainless steel, aluminum, and nickel.

  The sealing plate 5 is a container made of a conductive metal and having a shallow dish shape that accommodates the negative electrode 2. The sealing plate 5 becomes an external negative electrode terminal of the battery by contacting the negative electrode 2. Specifically, a metal container made of, for example, stainless steel can be used for the sealing plate 5.

  Further, a current collecting layer containing a conductive material such as a carbon material or a net-like conductive metal on the surface of the positive electrode case 6 that contacts the positive electrode and / or the surface of the sealing plate 5 that contacts the negative electrode. An electric body may be provided. Thereby, contact of an electrode can be performed appropriately. Contact between the positive electrode case and the positive electrode and / or contact between the sealing plate and the negative electrode can be improved.

The non-aqueous electrolyte includes, for example, a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, and lactones. These may be used alone or in combination of two or more. Examples of the lithium salt include LiClO ₄ , LiNCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiBF ₄ , and LiPF ₆ . These may be used alone or in combination of two or more.

  Hereinafter, the present invention will be described in detail based on examples.

<< Example 1-1-1 >>
[Synthesis of manganese-nickel composite oxide]
Manganese sulfate (Kanto Chemical Co., Ltd. special grade reagent) and nickel sulfate (Kanto Chemical Co., Ltd. special grade reagent) are mixed so that the atomic ratio (molar ratio) of manganese to nickel is 0.5: 0.5. Then, a mixed aqueous solution was prepared. In the mixed aqueous solution, the total concentration of sulfate was 1 mol / L.

  An aqueous solution (sodium hydroxide concentration 4 mol / L) containing sodium hydroxide (Kanto Chemical Co., Ltd. special grade reagent) was prepared. An aqueous solution in which manganese sulfate and nickel sulfate were dissolved was gradually added dropwise to this aqueous sodium hydroxide solution with stirring.

  After allowing the reaction solution to stand, the operation of discarding the supernatant and replenishing the ion exchange water was repeated until the supernatant became neutral. The hydroxide coprecipitate containing manganese and nickel produced at the bottom of the container was filtered off and dried to obtain a raw material containing manganese and nickel. In the obtained raw material, the atomic ratio of manganese to nickel was 0.5: 0.5.

  The obtained raw material was heat-treated at 250 ° C. for 20 hours in a mixed gas atmosphere of argon gas and oxygen gas having a partial pressure of oxygen gas of 200 MPa to obtain a manganese nickel composite oxide.

[Crystal structure analysis]
The X-ray diffraction chart of the manganese nickel composite oxide was measured using a powder X-ray diffractometer (X'Pert manufactured by Philips) equipped with a copper tube. The interplanar spacing d was determined from the peak position of the obtained X-ray diffraction chart, and the crystal structure was examined by comparing with the known compound.

[Composition analysis]
The obtained manganese nickel composite oxide was dissolved in aqua regia. The obtained solution was subjected to high frequency inductively coupled plasma (ICP) emission analysis to quantify the amount of constituent elements of the manganese nickel composite oxide. For ICP emission analysis, “ICPS-1000III” manufactured by Shimadzu Corporation was used. The content (weight) of manganese and nickel contained in the manganese-nickel composite oxide was determined by ICP emission analysis, and the content (weight) of the remainder was determined as the oxygen content (weight), and the composition (molar ratio) of the composite oxide was determined from these values. .

  In the following examples and comparative examples, the crystal structure and composition of the manganese nickel composite oxide were measured as described above.

[Production of positive electrode]
100 parts by weight of the obtained manganese-nickel composite oxide, 5 parts by weight of ketjen black (conductive material), and 5 parts by weight of polytetrafluoroethylene (binder) are mixed thoroughly to obtain a positive electrode A mixture was obtained. This positive electrode mixture was formed into a disk shape having a diameter of 20 mm and a thickness of 3.0 mm and dried under reduced pressure to obtain a positive electrode.

[Production of negative electrode]
A disk having a diameter of 20 mm was punched out of a hoop made of metallic lithium having a thickness of 1.0 mm to obtain a negative electrode.

[Production of battery]
A coin-type non-aqueous electrolyte secondary battery having a diameter of 24.5 mm and a thickness of 5.0 mm as shown in FIG. 1 was produced and designated as battery 1-1-1. The battery 1-1-1 was assembled in the following manner.
First, the positive electrode 1 was placed at the center of the inner bottom surface of the positive electrode case 6. On the positive electrode 1, a separator 3 made of polypropylene non-woven fabric was placed.
Next, the nonaqueous electrolyte was injected into the positive electrode case 6. The nonaqueous electrolyte was prepared by mixing LiN (CF ₃ SO ₂ ) ₂ in a mixed solvent obtained by mixing 40 parts by weight of propylene carbonate, 40 parts by weight of ethylene carbonate, and 20 parts by weight of 1,2-dimethoxyethane. It was prepared by dissolving at a concentration of 0 mol / L.
Then, the negative electrode 2 was press-contacted to the inner surface of the sealing plate 5 in which the gasket 4 was arrange | positioned at the peripheral part. The positive electrode case 6 and the sealing plate 5 are arranged so that the positive electrode 1 and the negative electrode 2 face each other with the separator 3 therebetween, and the opening end of the positive electrode case 6 is caulked with the sealing plate 5 to Was completed.

<< Example 1-1-2 >>
A manganese nickel composite oxide was prepared in the same manner as in Example 1-1-1 except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.6: 0.4 was used. Obtained. In the mixed aqueous solution used, the total concentration of sulfate was 1 mol / L. Moreover, in the obtained manganese nickel composite oxide, it was manganese: nickel = 0.6: 0.4.
Using this manganese nickel composite oxide, a battery 1-1-2 was obtained in the same manner as in Example 1-1-1.

<< Example 1-1-3 >>
A manganese nickel composite oxide was prepared in the same manner as in Example 1-1-1, except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.7: 0.3 was used. Obtained. In the mixed aqueous solution used, the total concentration of sulfate was 1 mol / L. Moreover, in the obtained manganese nickel composite oxide, it was manganese: nickel = 0.7: 0.3.
A battery 1-1-3 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Example 1-1-4 >>
A manganese nickel composite oxide was prepared in the same manner as in Example 1-1-1, except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.8: 0.2 was used. Obtained. In the mixed aqueous solution used, the total concentration of sulfate was 1 mol / L. Moreover, in the obtained manganese nickel composite oxide, it was manganese: nickel = 0.8: 0.2.
A battery 1-1-4 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Example 1-1-5 >>
A manganese nickel composite oxide was prepared in the same manner as in Example 1-1-1 except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.9: 0.1 was used. Obtained. In the mixed aqueous solution used, the total concentration of sulfate was 1 mol / L. Moreover, in the obtained manganese nickel composite oxide, it was manganese: nickel = 0.9: 0.1.
A battery 1-1-5 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Example 1-1-6 >>
A manganese nickel composite oxide was prepared in the same manner as in Example 1-1-1 except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.99: 0.01 was used. Obtained. In the mixed aqueous solution used, the total concentration of sulfate was 1 mol / L. Moreover, in the obtained manganese nickel composite oxide, it was manganese: nickel = 0.99: 0.01.
A battery 1-1-6 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Comparative Example 1-1-1 >>
Manganese oxide (MnO ₂ ) was obtained in the same manner as in Example 1-1-1, except that an aqueous solution having a manganese sulfate concentration of 1 mol / L was used.
A comparative battery 1-1-1 was obtained in the same manner as in Example 1-1-1, except that this manganese oxide was used.

<< Comparative Example 1-1-2 >>
A manganese nickel composite oxide was prepared in the same manner as in Example 1-1-1 except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.4: 0.6 was used. Obtained. In the mixed aqueous solution used, the total concentration of sulfate was 1 mol / L. Moreover, in the obtained manganese nickel composite oxide, it was manganese: nickel = 0.4: 0.6.
A comparative battery 1-1-2 was obtained in the same manner as in Example 1-1-1, except that this manganese nickel composite oxide was used.

<< Examples 1-2-1 to 1-2-6 and Comparative Examples 1-2-1 to 1-2-2 >>
Examples 1-1-1 to 1-1-6 and Comparative Example 1-1 except that the partial pressure of oxygen gas contained in the mixed gas atmosphere when heat-treating the raw material containing manganese and nickel was 20 MPa. In the same manner as -1 to 1-1-2, batteries 1-1-1 to 1-1-6 and comparative batteries 1-1-1 to 1-1-2 were obtained.

<< Examples 1-3-1 to 1-3-6 and Comparative Examples 1-3-1 to 1-3-2 >>
Examples 1-1-1 to 1-1-6 and Comparative Example 1 except that the partial pressure of the oxygen gas contained in the mixed gas atmosphere when heat-treating the raw material containing manganese and nickel was 2 MPa. In the same manner as 1-1 to 1-1-2, batteries 1-3-1 to 1-3-6 and comparative batteries 1-3-1 to 1-3-2 were obtained.

<< Examples 1-4-1 to 1-4-6 and Comparative Examples 1-4-1 to 1-4-2 >>
Examples 1-1-1 to 1-1-6 and Comparative Example 1 except that the partial pressure of the oxygen gas contained in the mixed gas atmosphere when heat-treating the raw material containing manganese and nickel was 0.1 MPa. In the same manner as in 1-1-1 and 1-1-2, batteries 1-4-1 to 1-4-6 and comparative batteries 1-4-1 to 1-4-2 were obtained.

<< Comparative Example 1-5-1 to Comparative Example 1-5-6 >>
Examples 1-1-1 to 1-1-6 and Comparative Example 1 except that the partial pressure of oxygen gas contained in the mixed gas atmosphere when heat-treating the raw material containing manganese and nickel was 0.02 MPa. Comparative batteries 1-5-1 to 1-5-6 were obtained in the same manner as in 1-1 to 1-1-2.

Table 1 shows the compositions and crystal structures of the positive electrode active materials prepared in Examples 1-1-1 to 1-4-6 and Comparative Examples 1-1-1 to 1-5-6. The “mixed crystal” in Table 1 means that the manganese nickel composite oxide is a mixed crystal of a γ phase manganese dioxide type crystal structure and a β phase manganese dioxide type crystal structure.
“+ NiO” is an oxide in which the obtained manganese-nickel composite oxide has the same crystal structure as that of nickel oxide (NiO) and / or NiO as impurities, but will contain some manganese It is meant to contain (Mn _1-x Ni _x O). The same applies to Tables 2 to 5 below.
Although the relative magnitude of the NiO content can be seen from the peak intensity of the powder X-ray diffraction, it is difficult to obtain the absolute value of the content using other analysis means.

<< Example 2-1-1 >>
A mixed aqueous solution of manganese nitrate and nickel nitrate having an atomic ratio of manganese to nickel of 0.5: 0.5 was prepared. In this mixed aqueous solution, the total concentration of nitrate was 1 mol / L.
This mixed aqueous solution was spray-dried in air at 80 ° C. to obtain a powdered nitrate mixture (raw material). This raw material was heat-treated at 250 ° C. for 20 hours in a mixed atmosphere (Ar + O ₂ ) with a partial pressure of oxygen gas of 200 MPa to obtain a manganese nickel composite oxide. In the obtained manganese nickel composite oxide, it was manganese: nickel = 0.5: 0.5.
A battery 2-1-1 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Example 2-1-2 to Example 2-1-6 >>
The atomic ratio of manganese and nickel in the mixed aqueous solution of manganese nitrate and nickel nitrate is 0.6: 0.4, 0.7: 0.3, 0.8: 0.2, 0.9: 0.1. Or 0.99: 0.01 Except having set it as 0.01, it carried out similarly to Example 2-1-1, and obtained the battery 2-1-2-2-1-6.

<< Comparative Example 2-1-1 >>
A comparative battery 2-1-1 was obtained in the same manner as in Example 2-1-1 except that an aqueous solution containing manganese nitrate at a concentration of 1 mol / L was used.

<< Comparative Example 2-1-2 >>
Comparative battery 2-1 was prepared in the same manner as in Example 2-1-1 except that a mixed aqueous solution of manganese nitrate and nickel nitrate having an atomic ratio of manganese to nickel of 0.4: 0.6 was used. 2 was produced. In the mixed aqueous solution used, the total concentration of nitrate was 1 mol / L.

<< Examples 2-2-1 to 2-2-6 and Comparative Examples 2-2-1 to 2-2-2 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 20 MPa, Example 2-1 to Example 2-1-6 and Comparative Example 2-1 to 2- In the same manner as in 1-2, a battery 2-2-1 to a battery 2-2-6 and a comparative battery 2-2-1 to 2-2-2 were obtained.

<< Examples 2-3-1 to 2-3-6 and Comparative Examples 2-3-1 to 2-3-2 >>
Examples 2-1-1 to 2-1-6 and Comparative Examples 2-1-1 to 2-1-2, except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 2 MPa Similarly, batteries 2-3-1 to 2-3-6 and comparative batteries 2-3-1 to 2-3-2 were obtained.

<< Examples 2-4-1 to 2-4-6 and Comparative Examples 2-4-1 to 2-4-2 >>
Examples 2-1-1 to 2-1-6 and Comparative Examples 2-1-1 to 2-1 except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 0.1 MPa -2 to batteries 2-4-1 to 2-4-6 and comparative batteries 2-4-1 to 2-4-2.

<< Comparative Example 2-5-1 to Comparative Example 2-5-6 >>
Comparative Battery 2-5 was made in the same manner as Example 2-1-1 to 2-1-6 except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 0.02 MPa. 1-2-5-6 was obtained.

  Table 2 shows the compositions and crystal structures of the positive electrode active materials prepared in Examples 2-1 to 2-4-6 and Comparative Examples 2-1-1 to 2-5-6. “Β” in Table 2 means a β-phase manganese dioxide type crystal structure.

<< Example 3-1-1 >>
A mixed aqueous solution of manganese acetate and nickel acetate having an atomic ratio of manganese and nickel of 0.5: 0.5 was prepared. In the mixed aqueous solution used, the total concentration of acetate was 1 mol / L.
This mixed aqueous solution was spray-dried in air at 80 ° C. to obtain a powdery acetate salt mixture (raw material). This raw material was heat-treated at 250 ° C. for 20 hours in a mixed atmosphere (Ar + O ₂ ) where the partial pressure of oxygen gas was 200 MPa to obtain a manganese-nickel composite oxide. In the obtained manganese nickel composite oxide, manganese: nickel = 0.5: 0.5.
A battery 3-1-1 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Example 3-1-2 to Example 3-1-6 >>
The atomic ratio of manganese to nickel in the mixed aqueous solution of manganese acetate and nickel acetate is 0.6: 0.4, 0.7: 0.3, 0.8: 0.2, 0.9: 0.1. Or 0.99: 0.01 Except having set it as 0.01, it carried out similarly to Example 3-1-1, and obtained the battery 3-1-2 to 3-1-6.

<< Comparative Example 3-1-1 >>
A comparative battery 3-1-1 was prepared in the same manner as in Example 3-1-1 except that an aqueous solution containing manganese acetate at a concentration of 1 mol / L was used instead of the mixed aqueous solution of manganese acetate and nickel acetate. Obtained.

<< Comparative Example 3-1-2 >>
Comparative battery 3-1 was prepared in the same manner as in Example 3-1-1 except that a mixed aqueous solution of manganese acetate and nickel acetate having an atomic ratio of manganese to nickel of 0.4: 0.6 was used. -2 was obtained. In the mixed aqueous solution, the total concentration of acetate was 1 mol / L.

<< Examples 3-2-1 to 2-3-2-6 and Comparative Examples 3-2-1 to 2-3-2 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 20 MPa, Examples 3-1-1 to 3-1-6 and Comparative Examples 3-1-1 to 3-1-1 In the same manner as in Example 2, batteries 3-2-1 to 2-3-6 and comparative batteries 3-2-1 to 3-2-2 were obtained.

<< Examples 3-1 to 3-3-6 and Comparative Examples 3-3-1 to 3-3-3 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 2 MPa, Examples 3-1-1 to 1-3-1 and Comparative Examples 3-1-1 to 3-1-1 In the same manner as in Example 2, the battery 3-3-1 to the battery 3-3-6 and the comparative battery 3-3-1 to 3-3-3 were obtained.

<< Example 3-4-1 to Example 3-4-6, Comparative Example 3-4-1, Comparative Example 3-4-2 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 0.1 MPa, Examples 3-1-1 to 1-3-1 and Comparative Examples 3-1-1 to 3- In the same manner as in 1-2, batteries 3-4-1 to 3-4-6 and comparative batteries 3-4-1 to 3-4-1 were obtained.

<< Comparative Example 3-5-1 to Comparative Example 3-5-6 >>
Comparative battery 3-5 was prepared in the same manner as in Examples 3-1-1 to 3-1-6 except that the partial pressure of oxygen gas contained in the mixed atmosphere when the raw material was heat-treated was 0.02 MPa. 1-3-5-6 were obtained.

  Table 3 shows the compositions and crystal structures of the positive electrode active materials prepared in Examples 3-1-1 to 3-4-6 and Comparative Examples 3-1-1 to 3-5-6. “Γ” in Table 3 means a γ-phase manganese dioxide type crystal structure.

<< Example 4-1-1 >>
A mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.5: 0.5 was prepared. In the obtained mixed aqueous solution, the total concentration of sulfate was 1 mol / L. Next, an aqueous sodium carbonate solution having a concentration of 3 mol / L was prepared. The mixed aqueous solution was gradually added dropwise to the aqueous sodium carbonate solution with stirring. A carbonate coprecipitate (raw material) containing manganese and nickel was obtained in the same manner as Example 1-1-1 except for the above.
A battery 4-1-1 was obtained in the same manner as in Example 1-1-1 except that this raw material was used.

<< Example 4-1-2 to Example 4-1-6 >>
The atomic ratio of manganese to nickel in the mixed aqueous solution of manganese sulfate and nickel sulfate is 0.6: 0.4, 0.7: 0.3, 0.8: 0.2, 0.9: 0.1. Or 0.99: 0.01 Except having set it as 0.01, it carried out similarly to Example 4-1-1, and obtained battery 4-1-2 to 4-1-6.

<< Comparative Example 4-1-1 >>
A comparative battery 4-1-1 was prepared in the same manner as in Example 4-1-1 except that an aqueous solution having a manganese sulfate concentration of 1 mol / L was used instead of the mixed aqueous solution of manganese sulfate and nickel sulfate. Obtained.

<< Comparative Example 4-1-2 >>
Comparative battery 4-1 in the same manner as in Example 4-1-1 except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.4: 0.6 was used. 2 was obtained. In the mixed aqueous solution, the total concentration of sulfate was 1 mol / L.

<< Examples 4-2-1 to 4-2-6 and Comparative Examples 4-2-1 to 4-2-2 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 20 MPa, Examples 4-1-1 to 4-1-6 and Comparative Examples 4-1-1 to 4-1 In the same manner as in Example 2, batteries 4-2-1 to 4-2-6 and comparative batteries 4-2-1 to 4-2-2 were obtained.

<< Example 4-3-1 to Example 4-3-6, Comparative Example 4-3-1, Comparative Example 4-3-2 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 2 MPa, Examples 4-1-1 to 4-1-6 and Comparative Examples 4-1-1 to 4-1 In the same manner as in Example 2, batteries 4-3-1 to 4-3-6 and comparative batteries 4-3-1 to 4-3-2 were obtained.

<< Examples 4-4-1 to 4-4-6 and Comparative Examples 4-4-1 to 4-4-2 >>
Except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 0.1 MPa, Examples 4-1-1 to 4-1-6 and Comparative Examples 4-1-1 to 4- In the same manner as in 1-2, batteries 4-4-1 to 4-4-6 and comparative batteries 4-4-1 to 4-4-2 were obtained.

<< Comparative Examples 4-5-1 to 4-5-6 >>
Comparative battery 4-5 was prepared in the same manner as in Examples 4-1-1 to 4-1-6, except that the partial pressure of oxygen gas contained in the mixed atmosphere when the raw material was heat-treated was 0.02 MPa. 1-4-5-6 was obtained.

  Table 4 shows the compositions and crystal structures of the positive electrode active materials prepared in Examples 4-1-1 to 4-4-6 and Comparative Examples 4-1-1 to 4-5-6. “New 2” in Table 4 is 0.473 ± 0.005 nm, 0.244 ± 0.005 nm, 0.215 ± 0.005 nm, 0.167 ± 0.005 nm, 0 in the powder X-ray diffraction chart. Means a novel crystal structure showing at least six X-ray diffraction peaks corresponding to a face spacing d of 148 ± 0.005 nm and 0.141 ± 0.005 nm. “Γ” means a γ-phase manganese dioxide type crystal structure.

<< Example 5-1-1 >>
In the same manner as in Example 4-1-1, a carbonate coprecipitate (raw material) containing manganese and nickel was produced. This raw material was heat-treated at 450 ° C. for 20 hours in a mixed atmosphere (Ar + O ₂ ) where the partial pressure of oxygen gas was 200 MPa to obtain a manganese-nickel composite oxide.
A battery 5-1-1 was obtained in the same manner as in Example 1-1-1 except that this manganese nickel composite oxide was used.

<< Example 5-1-2 to Example 5-1-6 >>
The atomic ratio of manganese and nickel contained in the mixed aqueous solution of manganese sulfate and nickel sulfate is 0.6: 0.4, 0.7: 0.3, 0.8: 0.2, 0.9: 0. .1 or 0.99: 0.01, except that the battery 5-1-2 to 5-1-6 was obtained in the same manner as in Example 5-1-1.

<< Comparative Example 5-1-1 >>
A comparative battery 5-1-1 was obtained in the same manner as in Example 5-1-1 except that a 1 mol / L manganese sulfate aqueous solution was used instead of the mixed aqueous solution of manganese sulfate and nickel sulfate.

<< Comparative Example 5-1-2 >>
Comparative battery 5-1 was prepared in the same manner as in Example 5-1-1 except that a mixed aqueous solution of manganese sulfate and nickel sulfate having an atomic ratio of manganese to nickel of 0.4: 0.6 was used. 2 was obtained. In the mixed aqueous solution, the total concentration of sulfate was 1 mol / L.

<< Examples 5-2-1 to 5-2-6 and Comparative Examples 5-2-1 to 5-2-2 >>
Examples 5-1-1 to 5-1-6 and Comparative Examples 5-1-1 to 5-1-2, except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 20 MPa In the same manner as described above, batteries 5-2-1 to 5-2-6 and comparative batteries 5-2-1 to 5-2-2 were obtained.

<< Examples 5-3-1 to 5-3-6 and Comparative Examples 5-3-1 to 5-3-2 >>
Except that the partial pressure of the oxygen gas contained in the mixed atmosphere when heat-treating the raw material was set to 2 MPa, Examples 5-1-1 to 5-1-6 and Comparative Examples 5-1-1 to 5-1 In the same manner as in Example 2, batteries 5-3-1 to 5-3-6 and comparative batteries 5-3-1 to 5-3-2 were obtained.

<< Examples 5-4-1 to 5-4-6 and Comparative Examples 5-4-1 to 5-4-2 >>
Except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 0.1 MPa, Examples 5-1-1 to 5-1-6 and Comparative Examples 5-1-1 to 5- In the same manner as in 1-2, batteries 5-4-1 to 5-4-6 and comparative batteries 5-4-1 to 5-4-2 were obtained.

<< Comparative Examples 5-5-1 to 5-5-6 >>
Comparative battery 5-5 was made in the same manner as Example 5-1-1 to 5-1-6, except that the partial pressure of oxygen gas contained in the mixed atmosphere when heat-treating the raw material was 0.02 MPa. 1-5-5-6 was obtained.

  Table 5 shows the compositions and crystal structures of the positive electrode active materials prepared in Examples 5-1-1 to 5-4-6 and Comparative Examples 5-1-1 to 5-5-6. “New 1” in Table 5 is 0.692 ± 0.005 nm, 0.490 ± 0.005 nm, 0.309 ± 0.005 nm, 0.240 ± 0.005 nm, 0 in the powder X-ray diffraction chart. Means a novel crystal structure showing at least seven X-ray diffraction peaks corresponding to a face spacing d of 183 ± 0.005 nm, 0.153 ± 0.005 nm, and 0.135 ± 0.005 nm. “Β” means a β-phase manganese dioxide type crystal structure.

<< Comparative Example 6 >>
A comparative battery 6 was produced in the same manner as in Example 1-1-1, except that manganese dioxide (manufactured by Mitsui Kinzoku Mining Co., Ltd.) mass-produced by the electrolytic synthesis method was used as the positive electrode active material.

[Evaluation]
(Initial capacity and charge / discharge cycle characteristics)
Each of the produced batteries was left in a 20 ° C. environment for 3 hours or more, and the battery temperature was set to 20 ° C. Thereafter, each battery was charged with a current of 8 mA until the battery voltage reached 3 V, and then the charged battery was discharged until the battery voltage dropped to 1 V. Such a charge / discharge cycle was repeated, and the discharge capacity was measured for each cycle. Thus, the number of cycles at which the discharge capacity was 50% of the discharge capacity (initial capacity) at the first cycle was determined. In addition, it can be said that it is a battery which has favorable charging / discharging cycling characteristics, so that there are many charging / discharging cycle counts until discharge capacity reduces to 50% of initial capacity.
The results are shown in Tables 6-10. “Initial capacity” in Tables 6 to 10 indicates the discharge capacity at the first cycle. “Number of cycles” means the number of charge / discharge cycles in which the discharge capacity is 50% of the initial capacity.

It can be seen from Tables 1 to 5 that manganese-nickel composite oxides having different crystal structures can be obtained depending on the type of raw material, the temperature of heat treatment, and the partial pressure of oxygen gas.
It can also be seen that the atomic ratio of manganese and nickel contained in the obtained manganese-nickel composite oxide is equal to the atomic ratio of manganese and nickel in the raw material.
In addition, when the nickel content is high, the oxygen content (atomic ratio) in the manganese nickel composite oxide tends to decrease, and this decrease is remarkable when heat treatment is performed at a low oxygen gas partial pressure. I know that there is.

  On the other hand, when the atomic ratio of oxygen contained in the manganese nickel composite oxide is smaller than 1.5, and even when the atomic ratio of oxygen contained in the manganese nickel composite oxide is 1.5 or more, the raw material is heat treated. In the case where the partial pressure of oxygen gas contained in the atmosphere is 0.02 MPa, nickel oxide (NiO) was included as an impurity.

From Tables 6-10, when there is much content of nickel contained in manganese nickel complex oxide, the tendency for cycling characteristics to become favorable is understood. In all the batteries of the examples, the number of cycles at which the discharge capacity becomes 50% of the initial capacity exceeds 40 times.
However, in the battery of the comparative example using the manganese nickel composite oxide not containing nickel, the number of cycles at which the discharge capacity was 50% of the initial capacity was less than 20 times.

There was a tendency for the initial capacity to decrease as the atomic ratio of nickel contained in the manganese nickel composite oxide increased. However, the initial capacity of the battery of the example was larger than the initial capacity of the battery using the conventional manganese dioxide (comparative battery 6). Specifically, even in the case of a battery using a manganese nickel composite oxide having the smallest nickel atomic ratio (ie, Mn _0.99 Ni _0.01 O _2-y ), the cycle characteristics are improved and the initial capacity is increased. Yes.
Conversely, a manganese nickel composite oxide having a high atomic ratio of nickel contains nickel oxide (NiO) as an impurity. The initial capacity of a comparative battery using such a manganese nickel composite oxide is that of the comparative battery 6. It was smaller than the initial capacity.

  As described above, depending on the type of raw material, the temperature of heat treatment, and the partial pressure of oxygen gas, manganese nickel composite oxides with different crystal structures can be obtained, and there is almost no difference in battery characteristics due to the difference in crystal structures. It was. That is, the effects of the present invention were recognized in any structure of the manganese nickel composite oxide obtained in the examples. Among them, the initial capacity of the battery containing the manganese nickel composite oxide having the γ phase manganese dioxide type crystal structure was slightly larger than the initial capacity of other batteries. For this reason, a manganese nickel composite oxide having a γ phase manganese dioxide type crystal structure is preferred.

  By using the non-aqueous electrolyte secondary battery active material obtained by the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery having mainly improved charge / discharge cycle characteristics. Such a non-aqueous electrolyte secondary battery can be used as a power source of equipment for various applications, and is particularly suitable for a main power source of electronic equipment, for example.

1 is a longitudinal sectional view schematically showing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

Explanation of symbols

1 Positive electrode 2 Negative electrode 3 Separator 4 Gasket 5 Sealing plate 6 Positive electrode case

Claims (6)

Including a step of heating a raw material containing manganese and nickel in an atmosphere having an oxygen gas pressure of 0.1 MPa to 200 MPa,
The raw material containing manganese and nickel includes a carbonate coprecipitate containing manganese and nickel, a hydroxide coprecipitate containing manganese and nickel, a mixture of nitrate containing nickel and nitrate containing nickel, and manganese. The manufacturing method of the active material for nonaqueous electrolyte secondary batteries containing at least 1 sort (s) selected from the group which consists of the mixture of the organic acid salt containing and the organic acid salt containing nickel. The following formula (1):
Mn _1-x Ni _x O _2-y (1)
(Wherein 0.01 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5)
The active material for nonaqueous electrolyte secondary batteries containing the manganese nickel complex oxide represented by these.   The manganese nickel composite oxide is 0.692 ± 0.005 nm, 0.490 ± 0.005 nm, 0.309 ± 0.005 nm, 0.240 ± 0.005 nm, 0.183 in the powder X-ray diffraction chart. The nonaqueous electrolyte secondary battery according to claim 2, which exhibits at least seven X-ray diffraction peaks corresponding to an interplanar spacing d of ± 0.005 nm, 0.153 ± 0.005 nm, and 0.135 ± 0.005 nm. Active material.   The manganese nickel composite oxide is 0.473 ± 0.005 nm, 0.244 ± 0.005 nm, 0.215 ± 0.005 nm, 0.167 ± 0.005 nm, 0.148 in the powder X-ray diffraction chart. The active material for a non-aqueous electrolyte secondary battery according to claim 2, which exhibits at least six X-ray diffraction peaks corresponding to an interplanar spacing d of ± 0.005 nm and 0.141 ± 0.005 nm.   The manganese nickel composite oxide has a γ phase manganese dioxide type crystal structure or a β phase manganese dioxide type crystal structure, or a mixed crystal of a γ phase manganese dioxide type and a β phase manganese dioxide type. 2. The active material for a non-aqueous electrolyte secondary battery according to 2.   A negative electrode, a positive electrode including the active material for a non-aqueous electrolyte secondary battery according to any one of claims 2 to 5, a separator disposed between the negative electrode and the positive electrode, and a non-aqueous electrolyte A non-aqueous electrolyte secondary battery.