JP2012206925A - Sodium, manganese, titanium and nickel composite oxide, method for manufacturing the same, and sodium secondary battery using the same as member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sodium, manganese, titanium and nickel composite oxide having a lamellar rock salt type crystal structure which utilizes sodium rich as a resource, and is suitable for the use of a positive electrode material for a sodium secondary battery that allows a high capacity, a method for manufacturing it, and a sodium secondary battery including an electrode including its active substance as a compositional member.SOLUTION: The sodium manganese titanium and nickel composite oxide is characterized in that the sodium manganese titanium and nickel composite oxide expressed by NaMnTiNiO(wherein 0<x≤1.0, 0.5≤y<1.0, 0<z≤0.5, and 0.5<y+z≤1.0) is its main component, and the crystal structure is a lamellar rock salt type crystal structure belonging to a rhombohedral crystal, and the method for manufacturing it and the sodium secondary battery including the compound as an electrode active substance are also provided.

Description

The present invention relates to a positive electrode material active material for a sodium secondary battery, a method for producing the same, and a sodium secondary battery using the same as a member.

Currently, in Japan, most of the secondary batteries installed in portable electronic devices such as mobile phones and notebook computers are lithium secondary batteries. In addition, lithium secondary batteries are expected to be put into practical use as large batteries for hybrid cars and power load leveling systems in the future, and their importance is increasing.

This lithium secondary battery mainly comprises a positive electrode and a negative electrode containing materials capable of reversibly occluding and releasing lithium, an electrolyte solution in which a lithium ion conductor is dissolved in a non-aqueous organic solvent, and a separator. Element.

Among these constituent elements, lithium cobalt oxide (LiCoO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), and lithium titanium oxide (Li ₄ Ti ₅ O) are considered as active materials for electrodes. ₁₂ ) and other metal materials such as metal lithium, lithium alloy and tin alloy, and carbon materials such as graphite and MCMB (mesocarbon microbeads).

For these materials, the voltage of the battery is determined by the difference in chemical potential in the lithium content of each active material, but a lithium potential battery that is excellent in energy density is capable of forming a large potential difference depending on the combination. It is the feature.

Among them, in the combination using a lithium cobalt oxide LiCoO ₂ active material having a layered rock salt structure and a carbon material as an electrode, a voltage close to 4V is possible, and charge / discharge capacity (amount of lithium that can be desorbed / inserted from the electrode) This combination of electrode materials is widely used in current lithium secondary batteries because of its large size and safety.

In the future, secondary batteries are expected to be large, high-power, long-life, such as automotive power supplies, large-capacity backup power supplies, and emergency power supplies. As a positive electrode material active material, a higher performance (high capacity) electrode active material has been required.

On the other hand, with the spread of large-sized storage batteries, the use of lithium with a small amount of resources is also a problem from the viewpoint of resources and costs, and the development of chemical batteries that do not use lithium has been required.

From such a viewpoint, in recent years, sodium secondary batteries using sodium instead of lithium have been studied. That is, if a secondary battery using sodium instead of lithium can be manufactured, an excellent secondary battery can be manufactured from the viewpoint of resources and cost.

At that time, a material configuration similar to that of the current lithium secondary battery is possible, and a battery configuration comprising an oxide-based positive electrode material active material, a carbon material-based negative electrode material active material, and a non-aqueous electrolyte solution has been studied. Yes.

That is, a sodium oxide system that can occlude and release sodium, has high reversibility, and has a large amount of occlusion is required as a positive electrode material.

In particular, if aiming at low cost of the secondary battery, it has been necessary to develop a positive electrode material that does not use cobalt, nickel, etc., which are scarce in resources, as active material constituent elements.

From this point of view, the manganese oxide active material has a voltage of about 3 V when sodium metal is used as the counter electrode, as in the case of lithium secondary batteries. The possibility of a material having a structure as a positive electrode active material for a sodium secondary battery has been studied.

Among them, sodium manganese oxide Na _0.44 MnO ₂ is currently under investigation because it has a good reversibility of sodium elimination / insertion reaction in the region of about 3 V on the basis of sodium. (Non-Patent Document 1)

This material is expected to be applied as an electrode material since the stability of the crystal structure and the ionic conductivity are improved by substituting a part of manganese with titanium. (Non-patent document 2, Patent document 1)

However, the capacity per weight of the oxide active material is only about 100 to 150 mA / g, and application to a high capacity sodium secondary battery has been difficult.

On the other hand, sodium manganese oxide NaMnO ₂ having a layered rock salt structure has been attracting attention as a high-capacity material because of its high sodium content.

Among them, sodium nickel manganese oxide (NaNi _0.5 Mn _0.5 O ₂ ) having a rhombohedral system and a layered rock salt structure of the space group R-3m has a potential flat portion of about 3 V on the basis of sodium. A discharge capacity of about 185 mAh / g has been reported. (See Patent Document 2 and Non-Patent Document 3)

However, since the known charge / discharge reaction of these materials uses a bivalent to tetravalent oxidation-reduction reaction of nickel contained, it is necessary to contain 50% or more of nickel with respect to the constituent transition metal element. Therefore, the secondary battery is not cost-effective and has been a problem.

Under such circumstances, an oxide system in which sodium, manganese, and titanium are main constituent elements and nickel is partially substituted in a system having a layered rock salt structure has not been studied.

Japanese Patent No. 4257426 Japanese Patent Application No. 2009-079178

F. Sauvage, L.A. Laffont, J.M. -M. Tarascon, E .; Baudrin, Inorganic Chemistry, 46, 3289-3294 (2007) F. Funabiki, H .; Hayagawa, N .; Kijima, J .; Akimoto, Electrochemical and Solid-State Letters, 12, F35-F38 (2009) S. Komaba, T .; Nakayama, A .; Ogata, T .; Shimizu, C.I. Takei, S .; Takada, A .; Hokuura, I. et al. Nakai, ECS Transactions, 16, 43-55 (2009)

Accordingly, the present invention solves the above-mentioned problems as described above, and a sodium manganese titanium nickel oxide active material having a layered rock-salt structure that is important as a positive electrode material for sodium secondary batteries that can be expected to have a high capacity, and a method for producing the same An object of the present invention is to provide a sodium secondary battery including an electrode containing the active material as a constituent member.

The present inventors have a result of intensive studies, the manufacturing method of high-temperature baking of the raw material compound, sodium manganese titanium-nickel composite oxide having a layered rock-salt structure _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu , 0 <x ≦ 1.0, 0.5 ≦ y <1.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0) can be confirmed. In a sodium secondary battery using an electrode made of sodium manganese titanium nickel composite oxide as a positive electrode active material, a high capacity exceeding 200 mAh / g and a reversible charge / discharge reaction were confirmed, and the present invention was completed. It came to do.

The present invention, sodium manganese titanium-nickel composite oxide _{Na x Mn y Ti z Ni 1} -y-z O 2 ( except Shikichu having a layered rock-salt structure shown below, 0 <x ≦ 1.0, 0.5 ≦ y <1.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0), and a manufacturing method thereof.

That is, the present _{invention, Na x Mn y Ti z Ni} 1-y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5 , 0.5 <y + z ≦ 1.0). A sodium manganese titanium-nickel composite oxide characterized by having a chemical composition.
The present _{invention, Na x Mn y Ti z Ni} 1-y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5, It is a sodium manganese titanium nickel composite oxide characterized by having a chemical composition of 0.5 <y + z ≦ 1.0) and having a crystal structure of a layered rock salt structure.
The present invention _{further, Na x Mn y Ti z Ni} 1-y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5, A sodium manganese titanium-nickel composite oxide having a chemical composition of 0.5 <y + z ≦ 1.0) and having a crystal structure of a layered rock salt structure belonging to a rhombohedral system.
Furthermore, the present invention includes mixing as a starting material a hydroxide containing sodium acetate and one or more of manganese, titanium, and nickel at a predetermined atomic ratio, and firing at a high temperature at a temperature of 400 ° C. to 1000 ° C. _{Na x Mn y Ti z Ni 1} -y-z O 2 ( except Shikichu, characterized by combining, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0. 5. A method for producing a sodium manganese titanium-nickel composite oxide, characterized by having a chemical composition of 5, 0.5 <y + z ≦ 1.0).
In the method for producing a sodium manganese titanium nickel composite oxide of the present invention, a hydroxide containing at least one of manganese, titanium and nickel as a starting material is obtained in advance by a coprecipitation method. Can be used.
Furthermore, the present invention relates to a sodium secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte, and a sodium secondary battery using a positive electrode containing the sodium manganese titanium nickel composite oxide of the present invention as an electrode active material of the positive electrode. It is also a thing.

According to the present invention, sodium manganese titanium-nickel composite oxide having a layered rock-salt structure _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0), and sodium using an electrode prepared using this sodium manganese titanium nickel composite oxide as a positive electrode active material In the secondary battery, high capacity and charge / discharge characteristics with high reversibility are possible.

It is a schematic diagram which shows one example of a sodium secondary battery. _{2 is} an X-ray powder diffraction _pattern of sodium manganese titanium nickel composite oxide Na _0.57 Mn _0.51 Ti _0.23 Ni _0.26 O ₂ of the present invention obtained in Example 1. FIG. 2 is an X-ray powder diffraction pattern of the sodium manganese titanium composite oxide and sodium manganese oxide of the present invention obtained in Examples 2 to 5 and Comparative Example 1. FIG. It is a X-ray powder diffraction pattern of the sodium manganese titanium nickel composite oxide of this invention obtained in Example 6-12. _{4 is} an X-ray powder diffraction _pattern of sodium manganese titanium nickel composite oxide Na _1.0 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ of the present invention obtained in Example 13. FIG. It shows the voltage change due to charging and discharging of the sodium secondary battery using the sodium-manganese-titanium composite oxide _Na 0.59 _Mn 0.90 _{Ti 0.10} O ₂ of the present invention obtained in Example 5 as an electrode active material FIG. For charge and discharge of a sodium secondary battery using the sodium manganese titanium nickel composite oxide Na _1.0 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ of the present invention obtained in Example 13 as an electrode active material It is a figure which shows the accompanying voltage change.

As a result of intensive studies on a method for producing a sodium manganese titanium-nickel composite oxide having a layered rock salt structure using a raw material compound containing a constituent element as a starting material, the present inventors have found that the layered rock salt structure belonging to the rhombohedral system and since _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5,0.5 <Y + z ≦ 1.0) was found to be possible to produce, and it was found to be a compound having a novel chemical composition having the same structure.

As a result, compared with the sodium manganese oxide system having a known layered rock salt type structure, the positive electrode produced using the sodium manganese titanium nickel composite oxide having the layered rock salt type structure belonging to the rhombohedral system of the present invention as an active material In the sodium secondary battery using the above, the initial capacity exceeding 200 mAh / g and the reversible charge / discharge behavior were confirmed, and the present invention was completed.

Sodium manganese titanium-nickel composite oxide of the present _{invention, Na x Mn y Ti z Ni} 1-y-z O 2 ( except Shikichu the starting compound was prepared by high temperature firing as the starting material containing the constituent elements, 0 <X ≦ 1.0, 0.5 ≦ y <1.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0).
It is a compound characterized by taking a layered rock salt type structure as a characteristic of its crystal structure.
As a more detailed feature of the layered rock salt structure, the crystal system is a compound belonging to the rhombohedral system.
The method for producing the sodium manganese titanium nickel composite oxide is characterized by firing at a high temperature at a temperature of 400 ° C. or higher and 1000 ° C. or lower using a raw material compound containing a constituent element as a starting material.
A more detailed production method is characterized in that the starting material is synthesized using a hydroxide containing one or more of manganese, titanium, and nickel.
Furthermore, this sodium manganese titanium nickel composite oxide can be used as a positive electrode material active material in a storage battery and a sodium secondary battery.

The production method according to the present invention will be described in more detail.
(Sodium manganese titanium-nickel composite oxide _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0 .5, 0.5 <y + z ≦ 1.0))
Sodium manganese titanium-nickel composite oxide _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu of the present invention, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0) is a raw material of sodium metal or at least one of sodium compounds, manganese metal or at least one of manganese compounds, titanium metal, or titanium compounds. at least one, at least _{one, Na x Mn y Ti z Ni} 1-y-z O 2 ( although Shikichu nickel metal or a nickel compound,, 0 <x ≦ 1.0,0.5 ≦ y <1 0.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0) by weighing and mixing so as to have a chemical composition, and heating in an atmosphere in which oxygen gas exists such as in air, Can be manufactured.

Alternatively, as a starting material, sodium, manganese, titanium, using a compound consisting of two or more of _{nickel, Na x Mn y Ti z Ni} 1-y-z O 2 ( although Shikichu, 0 <x ≦ 1. 0, 0.5 ≤ y <1.0, 0 <z ≤ 0.5, 0.5 <y + z ≤ 1.0) Weigh and mix so that there is oxygen gas in the air It can manufacture by heating in the atmosphere to do.

As the sodium raw material, at least one of sodium (metallic sodium) and a sodium compound is used. The sodium compound is not particularly limited as long as it contains sodium. For example, acetates such as CH ₃ COONa, CH ₃ COONa · 3H ₂ O, salts such as NaNO ₃ , hydroxides such as NaOH, Na ₂ Examples thereof include oxides such as O and Na ₂ O ₂ and carbonates such as Na ₂ CO ₃ . Or already sodium titanium oxide such as _{Na 2 TiO 3, Na 2 Ti} 3 O 7, sodium manganese oxides such as NaMnO _2, sodium nickel oxide and going on compounds such as NaNiO ₂ and the like. Among these, CH ₃ COONa, which has high reactivity even at a low temperature of 500 ° C. or lower, is preferable.

As the manganese raw material, at least one of manganese (metallic manganese) and a manganese compound is used. The manganese compound is not particularly limited as long as it contains manganese, and examples thereof include oxides such as MnO, Mn ₂ O ₃ , Mn ₃ O ₄ , and MnO ₂ , and hydroxides such as MnOH and MnOOH. . Among these, manganese hydroxide and the like are preferable.

As the titanium raw material, at least one of titanium (metallic titanium) and a titanium compound is used. The titanium compound is not particularly limited as long as it contains titanium, and examples thereof include oxides such as TiO, Ti ₂ O ₃ and TiO ₂ , salts such as TiCl _{4 and the} like. Or the hydroxide etc. which are already manganese titanium compounds are mentioned. Among these, manganese titanium hydroxide having high reactivity even at a low temperature of 600 ° C. or lower is preferable.

As the nickel raw material, at least one of nickel (metallic nickel) and a nickel compound is used. The nickel compound is not particularly limited as long as it contains nickel, and examples thereof include oxides such as NiO and hydroxides such as NiOH and NiOOH. Or the hydroxide already used as the manganese nickel compound, the hydroxide used as the manganese titanium nickel compound, etc. are mentioned. Among these, manganese titanium nickel hydroxide and the like are preferable because they are highly reactive even at a low temperature of 500 ° C. or lower and hardly generate impurities.

First, a mixture containing these is prepared. The mixing ratio of the respective elements _{are, Na x Mn y Ti z Ni} 1-y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0 0.5, 0.5 <y + z ≦ 1.0) is preferably mixed so as to have a chemical composition. Further, since sodium easily volatilizes during heating, it is better to make the amount slightly excessive, and preferably within the range of 0.5 to 1.1. Moreover, a mixing method is not specifically limited as long as these can be mixed uniformly, For example, what is necessary is just to mix by a wet type or a dry type using well-known mixers, such as a mixer.

The mixture is then fired. The firing temperature can be appropriately set depending on the raw materials, but is usually about 400 ° C to 1000 ° C, preferably 450 ° C to 650 ° C. Also, the firing atmosphere is not particularly limited, and it is usually performed in an oxidizing atmosphere or air.

The firing time can be appropriately changed according to the firing temperature and the like. The cooling method is not particularly limited, but may be natural cooling (cooling in the furnace) or slow cooling.

After firing, the fired product may be pulverized by a known method as necessary, and the above firing step may be performed. However, in order to suppress sodium volatilization, it is preferable to perform firing once. Note that the degree of pulverization may be adjusted as appropriate according to the firing temperature and the like.

(Sodium secondary battery)
Sodium secondary battery of the present invention, the sodium manganese titanium-nickel composite oxide _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y < A positive electrode containing 1.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0) as an active material is used as a constituent member. That is, a battery element of a known sodium battery (coin type, button type, cylindrical type, all solid type, etc.) can be employed as it is except that the sodium manganese titanium nickel composite oxide of the present invention is used as the positive electrode material active material. it can. FIG. 1 is a schematic view showing an example in which the sodium secondary battery of the present invention is applied to a coin-type sodium secondary battery. The coin-type battery 1 includes a negative electrode terminal 2, a negative electrode 3, a (separator + electrolyte) 4, an insulating packing 5, a positive electrode 6, and a positive electrode can 7.

In the present invention, the sodium manganese titanium nickel composite oxide active material of the present invention is mixed with a conductive agent, a binder or the like as necessary to prepare a positive electrode mixture, and this is crimped to a current collector. Thus, a positive electrode can be produced. As the current collector, a stainless mesh, an aluminum mesh, an aluminum foil or the like can be preferably used. As the conductive agent, acetylene black, ketjen black or the like can be preferably used. As the binder, tetrafluoroethylene, polyvinylidene fluoride, or the like can be preferably used.

The composition of the sodium manganese titanium nickel composite oxide active material, the conductive agent, the binder and the like in the positive electrode mixture is not particularly limited, but usually the conductive agent is about 1 to 30% by weight (preferably 5 to 25% by weight). ), The binder may be 0 to 30% by weight (preferably 3 to 10% by weight), and the balance may be the sodium manganese titanium nickel composite oxide active material of the present invention.

In the sodium secondary battery of the present invention, the counter electrode with respect to the positive electrode functions as a negative electrode such as metallic sodium, sodium alloy, and carbon-based materials such as graphite and MCMB (mesocarbon microbeads), and occludes and releases sodium. Possible known ones can be employed.

Moreover, in the sodium secondary battery of the present invention, a known battery element may be adopted for the separator, the battery container, and the like.

Furthermore, known electrolyte solutions, solid electrolytes, and the like can be applied as the electrolyte. For example, as the electrolytic solution, an electrolyte such as sodium perchlorate dissolved in a solvent such as propylene carbonate (PC) or ethylene carbonate (EC) can be used.

Hereinafter, examples will be shown to further clarify the features of the present invention. The present invention is not limited to these examples.

(Synthesis of sodium manganese titanium nickel composite oxide Na _0.57 Mn _0.51 Ti _0.22 Ni _0.26 O ₂ )
An atomic weight of sodium acetate (CH ₃ COONa) powder having a purity of 99% or more and manganese titanium nickel hydroxide powder (Mn: Ti: Ni = 0.50: 0.25: 0.25) obtained by a coprecipitation method The ratio of Na: Mn: Ni: Ti was 0.7: 0.50: 0.25: 0.25. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer (trade name: RINT2550V, manufactured by Rigaku), it was found to be a rhombohedral single phase having good crystallinity. . The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.289 nm ± 0.001 nm
c = 1.485 nm ± 0.002 nm

Furthermore, when the chemical composition of the obtained compound was analyzed by ICP emission analysis (trade name VISTA-Pro, manufactured by VARIAN), Na _0.57 Mn _0.51 Ti _0.22 Ni _0.26 O ₂ was analyzed. It became clear that it was a composition formula.

(Synthesis of sodium manganese titanium composite oxide Na _0.56 Mn _0.53 Ti _0.47 O ₂ )
A manganese titanium hydroxide powder obtained by coprecipitation in advance with a composition ratio of sodium acetate (CH ₃ COONa) powder of purity 99% or more and manganese titanium having a composition of Mn: Ti = 0.51: 0.49. It measured so that it might become Na: M (M = Mn, Ti) = 0.7: 1.0 by atomic weight ratio. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was revealed that none of the obtained compounds was an almost single phase belonging to the rhombohedral system although the crystallinity was not so high. The powder X-ray diffraction pattern at this time is shown in FIG.

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the chemical composition formula was Na _0.56 Mn _0.53 Ti _0.47 O ₂ .

(Synthesis of sodium manganese titanium composite oxide Na _0.64 Mn _0.70 Ti _0.30 O ₂ )
A manganese titanium hydroxide powder having a composition ratio of sodium acetate (CH ₃ COONa) having a purity of 99% or more and manganese titanium having a composition of Mn: Ti = 0.67: 0.33 and obtained in advance by a coprecipitation method. It measured so that it might become Na: M (M = Mn, Ti) = 0.7: 1.0 by atomic weight ratio. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was revealed that none of the obtained compounds was an almost single phase belonging to the rhombohedral system although the crystallinity was not so high. The powder X-ray diffraction pattern at this time is shown in FIG.

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the chemical composition formula was Na _0.64 Mn _0.70 Ti _0.30 O ₂ .

(Synthesis of sodium manganese titanium composite oxide Na _0.59 Mn _0.80 Ti _0.20 O ₂ )
A manganese titanium hydroxide powder obtained by coprecipitation in advance with a composition ratio of sodium acetate (CH ₃ COONa) powder having a purity of 99% or more and manganese titanium having a composition of Mn: Ti = 0.77: 0.23. It measured so that it might become Na: M (M = Mn, Ti) = 0.7: 1.0 by atomic weight ratio. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was revealed that none of the obtained compounds was an almost single phase belonging to the rhombohedral system although the crystallinity was not so high. The powder X-ray diffraction pattern at this time is shown in FIG.

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the chemical composition formula was Na _0.59 Mn _0.80 Ti _0.20 O ₂ .

(Synthesis of sodium manganese titanium composite oxide Na _0.59 Mn _0.90 Ti _0.10 O ₂ )
A manganese titanium hydroxide powder having a composition ratio of sodium acetate (CH ₃ COONa) having a purity of 99% or more and manganese titanium having a composition of Mn: Ti = 0.89: 0.11 and obtained in advance by a coprecipitation method. It measured so that it might become Na: M (M = Mn, Ti) = 0.7: 1.0 by atomic weight ratio. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was revealed that none of the obtained compounds was an almost single phase belonging to the rhombohedral system although the crystallinity was not so high. The powder X-ray diffraction pattern at this time is shown in FIG.

Furthermore, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the chemical composition formula was Na _0.59 Mn _0.90 Ti _0.10 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.56 Ti _0.24 Ni _0.20 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) powder and the same manganese titanium hydroxide (Mn: Ti: Ni = 0.77: 0.23) at an atomic weight ratio of Na: Mn: Ni: Ti = 1.0: 0.56: 0. 20: 0.24 was weighed. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.289 nm ± 0.001 nm
c = 1.679 nm ± 0.001 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that it was a composition formula of Na _1.0 Mn _0.56 Ti _0.24 Ni _0.20 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) Powder and the same manganese titanium hydroxide (Mn: Ti: Ni = 0.77: 0.23) in terms of atomic weight ratio Na: Mn: Ni: Ti = 1.0: 0.61: 0. 24: Weighed to 0.15. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.289 nm ± 0.001 nm
c = 1.678 nm ± 0.001 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that it was a composition formula of Na _1.0 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.67 Ti _0.23 Ni _0.10 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) powder and the same manganese titanium hydroxide (Mn: Ti: Ni = 0.77: 0.23) at an atomic weight ratio of Na: Mn: Ni: Ti = 1.0: 0.67: 0. 23: Weighed to be 0.10. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.288 nm ± 0.001 nm
c = 1.678 nm ± 0.002 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the composition formula was Na _1.0 Mn _0.67 Ti _0.23 Ni _0.10 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.72 Ti _0.23 Ni _0.05 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) powder and the same manganese titanium hydroxide (Mn: Ti: Ni = 0.77: 0.23) at an atomic weight ratio of Na: Mn: Ni: Ti = 1.0: 0.72: 0. Weighed to be 23: 0.05. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.287 nm ± 0.001 nm
c = 1.672 nm ± 0.002 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the composition formula was Na _1.0 Mn _0.72 Ti _0.23 Ni _0.05 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.0.90 Ti _0.05 Ni _0.05 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) The powder and the same manganese hydroxide were weighed so that the atomic weight ratio was Na: Mn: Ni: Ti = 1.0: 0.90: 0.05: 0.05. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.286 nm ± 0.001 nm
c = 1.675 nm ± 0.005 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that it was a composition formula of Na _1.0 Mn _0.90 Ti _0.05 Ni _0.05 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.80 Ti _0.10 Ni _0.10 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) The powder and the manganese hydroxide were weighed so that the atomic weight ratio was Na: Mn: Ni: Ti = 1.0: 0.80: 0.10: 0.10. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.286 nm ± 0.001 nm
c = 1.673 nm ± 0.004 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that it was a composition formula of Na _1.0 Mn _0.80 Ti _0.10 Ni _0.10 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _1.00 Mn _0.0.70 Ti _0.15 Ni _0.15 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) The powder and the manganese hydroxide were weighed so that the atomic weight ratio was Na: Mn: Ni: Ti = 1.0: 0.70: 0.15: 0.15. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.288 nm ± 0.001 nm
c = 1.679 nm ± 0.002 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that it was a composition formula of Na _1.0 Mn _0.70 Ti _0.15 Ni _0.15 O ₂ .

(Synthesis of sodium manganese titanium nickel composite oxide Na _0.7 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ )
Sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O) powder having a purity of 99% or more and manganese titanium nickel hydroxide (Mn: Ti: Ni = 0.50: 0.25) obtained by coprecipitation method : 0.25) Powder and the same manganese titanium hydroxide (Mn: Ti: Ni = 0.77: 0.23) at an atomic weight ratio of Na: Mn: Ni: Ti = 0.7: 0.61: 0. 24: Weighed to 0.15. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that it was a substantially single phase of a layered rock salt structure belonging to a rhombohedral system having good crystallinity. The powder X-ray diffraction pattern at this time is shown in FIG. In addition, when the lattice constant was obtained by the least square method using each index and the spacing between the surfaces, the following values were obtained, and it was confirmed from the lattice constant that the layered rock salt structure had a new chemical composition.
a = 0.288 nm ± 0.001 nm
c = 1.678 nm ± 0.002 nm

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that it was a composition formula of Na _0.7 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ .

(Sodium secondary battery)
Sodium manganese titanium composite oxide Na _0.59 Mn _0.90 Ti _0.10 O ₂ obtained in Example 5 was used as an active material, acetylene black as a conductive agent, and tetrafluoroethylene as a binder in a weight ratio. An electrode is prepared by blending so as to be 45:45:10, and a 1M solution in which sodium perchlorate is dissolved in a propylene carbonate (PC) solvent using sodium metal as a counter electrode is used as an electrolytic solution. A sodium secondary battery (coin-type cell) having the structure shown in FIG. The battery was produced according to a known cell configuration / assembly method.

The manufactured sodium secondary battery was subjected to a constant current charge / discharge test under a temperature density of 25 mA at a current density of 30 mA / g and a cutoff potential of 4.2 V to 1.5 V. It was found that it was possible to charge and discharge at 4 V with an initial charge capacity of 82 mAh / g and an initial discharge capacity of 178 mAh / g. The voltage change accompanying the first charge / discharge reaction is shown in FIG. In addition, it was confirmed that by setting the upper limit charging voltage to 4.5 V, the capacity could be further increased, and the discharge capacity exceeded 200 mAh / g. From the above, it was revealed that Na _0.59 Mn _0.90 Ti _0.10 O _{2 of} the present invention is useful as a positive electrode material active material for a high-capacity sodium secondary battery.

(Sodium secondary battery)
Sodium manganese titanium nickel composite oxide Na _0.7 Mn _0.61 Ti _0.24 Ni _0.15 O ₂ obtained in Example 13 was used as an active material, acetylene black as a conductive agent, and tetrafluoroethylene as a binder. Were mixed so that the weight ratio would be 45:45:10, an electrode was prepared, and a 1M solution in which sodium perchlorate was dissolved in a propylene carbonate (PC) solvent using sodium metal as the counter electrode was used as the electrolyte. A sodium secondary battery (coin-type cell) having the structure shown in FIG. 1 was prepared, and its charge / discharge characteristics were measured. The battery was produced according to a known cell configuration / assembly method.

About the produced sodium secondary battery, when a constant current charging / discharging test was conducted under the temperature condition of 25 ° C. with a current density of 30 mA / g and a cutoff potential of 4.5V-1.5V, an average discharge potential of 2. It was found that charging and discharging can be repeated at 9 V with a charge capacity of about 170 mAh / g and a discharge capacity of about 150 mAh / g. FIG. 7 shows voltage changes associated with charge / discharge reactions in the second and third cycles. Compared with Example 14, the capacity was slightly reduced by replacing nickel, but it was found that the operating voltage could be higher, and the effect of nickel replacement became clear. From the above, it was revealed that Na _0.7 Mn _0.61 Ti _0.24 Ni _0.15 O _{2 of} the present invention is useful as a positive electrode material active material for a high-capacity sodium secondary battery.

(Comparative Example 1)
(Synthesis of sodium manganese oxide)
Sodium acetate (CH ₃ COONa) powder having a purity of 99% or more and manganese hydroxide powder obtained by the coprecipitation method were weighed so that the atomic weight ratio was Na: Mn = 0.7: 1.0. These were mixed in a mortar, filled in an alumina crucible, and baked at 500 ° C. in air for 12 hours using an electric furnace. Thereafter, it was naturally cooled in an electric furnace to obtain a starting material.

When the crystal structure of the obtained compound was examined by a powder X-ray diffractometer, it was found that although the crystallinity was not so high, it was an almost single phase belonging to the rhombohedral system. The powder X-ray diffraction pattern at this time is shown in FIG.

Further, when the chemical composition of the obtained compound was analyzed by ICP emission analysis, it was revealed that the chemical composition formula was Na _0.47 MnO ₂ .

DESCRIPTION OF SYMBOLS 1 Coin type sodium secondary battery 2 Negative electrode terminal 3 Negative electrode 4 Solid electrolyte 5 Insulation packing 6 Positive electrode 7 Positive electrode can

Claims (6)

_{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5,0.5 <y + z A sodium manganese titanium-nickel composite oxide having a chemical composition of ≦ 1.0). _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5,0.5 <y + z A sodium manganese titanium-nickel composite oxide having a chemical composition of ≦ 1.0) and a crystal structure of a layered rock salt type structure. _{Na x Mn y Ti z Ni 1} -y-z O 2 ( although Shikichu, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5,0.5 <y + z ≦ 1.0) and a crystal structure is a layered rock salt structure belonging to a rhombohedral system. As a starting material, it is synthesized by mixing sodium acetate and a hydroxide containing one or more of manganese, titanium and nickel at a predetermined atomic ratio and firing at a high temperature of 400 ° C. to 1000 ° C. _{Na x Mn y Ti z Ni 1} -y-z O 2 ( except Shikichu to, 0 <x ≦ 1.0,0.5 ≦ y <1.0,0 <z ≦ 0.5,0.5 The manufacturing method of the sodium manganese titanium nickel composite oxide which has a chemical composition of <y + z <= 1.0). Manganese, titanium, hydroxide containing one or more _{nickel, Na x Mn y Ti z Ni} 1-y-z O 2 as described in claim 4 is a hydroxide obtained in advance coprecipitation (Wherein, sodium manganese titanium nickel having a chemical composition of 0 <x ≦ 1.0, 0.5 ≦ y <1.0, 0 <z ≦ 0.5, 0.5 <y + z ≦ 1.0) A method for producing a composite oxide. In the sodium secondary battery containing a positive electrode, a negative electrode, a separator, and electrolyte, the positive electrode which contains the sodium manganese titanium nickel composite oxide of any one of the said Claim 1 to 3 as an electrode active material of a positive electrode is used. Sodium secondary battery.

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