JP2009227505A - Manganese oxide, electrode active material for battery, those producing methods and secondary battery using electrode active material for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manganese oxide which is excellent in a charge and discharge cycle for a long term, where high capacity can be expected and which is important as an inexpensive electrode material for a battery, an electrode active material for the battery, those producing methods and a secondary battery using the electrode active material for the battery. <P>SOLUTION: The manganese oxide has a chemical composition represented by general formula: Na<SB>x</SB>Ca<SB>y</SB>Mn<SB>9-z</SB>Ti<SB>z</SB>O<SB>18</SB>(wherein, composition range is 0<x<9; 0<y<1.8; and 0≤z≤5) and contains sodium, calcium, manganese, titanium, and oxygen as main ingredients. There are also provided the electrode active material for the battery, those producing methods, and the secondary battery using the electrode active material for the battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a manganese oxide, a battery electrode active material, a method for producing the same, and a secondary battery using the battery electrode active material.

  Currently, in Japan, many manganese oxides are used for electrodes in portable game machines, alkaline batteries for cameras, lithium batteries, or lithium secondary batteries mounted on portable electronic devices such as mobile phones and laptop computers. Used as a material. In the future, in addition to the demand for portable electronic devices so far, the importance of batteries as an emergency backup power source and distributed power source is increasing.

  This lithium secondary battery uses a positive electrode having a lithium-containing transition metal composite oxide as an active material and a material capable of inserting and extracting lithium, such as lithium metal, lithium alloy, metal oxide, and carbon. The main component is a negative electrode and a separator or solid electrolyte containing a non-aqueous electrolyte.

Among these constituent elements, the layered rock salt type lithium cobalt oxide (LiCoO ₂ ), the layered rock salt type lithium nickel oxide (LiNiO ₂ ), the spinel type lithium manganese oxide (LiMnM) are considered as the positive electrode active material. ₂ O ₄ ).

In particular, in a battery in which a lithium cobalt oxide LiCoO ₂ positive electrode active material and a carbon material are used as a negative electrode, a voltage close to 4 V is possible, and the charge / discharge capacity (the amount of lithium that can be desorbed and inserted from the positive electrode) is also large. Lithium cobalt oxide positive electrodes are widely used in current lithium secondary batteries.

However, the cobalt of LiCoO ₂ is a rare metal, which causes a rise in the price of lithium secondary batteries due to the rising price of cobalt. In addition, the battery industry accounts for about 20% of global cobalt production, and is expected to be unable to meet future demand growth.

On the other hand, LiNiO ₂ uses nickel, which is cheaper than cobalt, and is advantageous over lithium cobalt oxide in terms of price, and the battery capacity can be higher than lithium cobalt oxide. Therefore, it is considered as an effective alternative material for LiCoO ₂ .

However, a lithium secondary battery using LiNiO ₂ as a positive electrode material has a risk of decomposition, heat generation, ignition and the like when held at a high temperature due to the instability of the positive electrode active material in a charged state. There are many.

On the other hand, spinel-type lithium manganese oxide LiMn ₂ O ₄ has a disadvantage that its capacity is small compared to lithium cobalt oxide and lithium nickel oxide, but uses manganese which is cheaper than cobalt and nickel, and It is also excellent in terms of safety during charging. For this reason, it has been attracting attention as a battery material for portable game machines and automobiles where safety is important.

  However, this spinel type lithium manganese oxide has a problem that the battery capacity is remarkably reduced when the battery is repeatedly charged and discharged, that is, the charge / discharge cycle characteristics are poor. Furthermore, there has been a problem of high temperature storage deterioration that the battery capacity is remarkably reduced when the battery is stored at a high temperature of 60 ° C. or higher for a long period of time.

  In the future, it is expected that rechargeable secondary batteries such as lithium secondary batteries and capacitors will require large-sized, long-life batteries such as automotive power supplies, large-capacity backup power supplies, and stationary power supplies. Therefore, there has been a need for an electrode active material that contributes to a long life utilizing resource-rich manganese oxide.

Therefore, Na ₄ Mn ₉ O ₁₈ type materials having a tunnel structure in which the stability of the crystal structure is higher than that of the spinel structure, charge / discharge can be performed at a high potential, and a high capacity is possible have been studied. (See Patent Documents 1 to 4, Non-Patent Documents 1 and 2)

  The above material can be produced by exchanging sodium for lithium by an ion exchange synthesis method, and has attracted attention as an electrode material for a lithium secondary battery having a low cost and a high potential and a high capacity.

  Further, it has been clarified that the capacity can be further increased by replacing a part of manganese with titanium.

  However, in a lithium secondary battery using the above-mentioned material as a positive electrode, cycle deterioration due to charge / discharge is remarkable, and it is a problem that a high capacity in an initial cycle cannot be maintained for a long time.

In addition, regarding the sodium manganese oxide of the above material, a compound Na _1.1 Ca _1.8 Mn ₉ O ₁₈ in which sodium is substituted with calcium has been reported. There is no disclosure about the application of this calcium-substituted product to a secondary battery electrode active material. (Non Patent Literature 3)
JP 2005-259362 A JP 2005-263583 A JP 2005-268127 A Japanese Patent Application No. 2007-524578 J. et al. Akimoto, J. et al. Awaka, Y. et al. Takahashi, N .; Kijima, M .; Tabuchi, A .; Nakashima, H .; Sakabe, K .; Tatsumi, Electrochemical and Solid-State Letters, 8, A554-A557 (2005) J. et al. Awaka, J. et al. Akimoto, H. et al. Hayagawa, Y .; Takahashi, N .; Kijima, M .; Tabuchi, H .; Sakabe, K .; Tatsumi, Journal of Power Sources, 174, 1218-1223 (2007) N. Floros, C.I. Michel, M.M. Hervieu, B.H. Raveau, Journal of Solid State Chemistry, 162, 34-41 (2001)

  The present invention solves the problems of the existing positive electrode materials as described above, is excellent in long-term charge / discharge cycle, can be expected to have a high capacity, and is an important manganese oxide and battery electrode as a low-cost battery electrode material An active material, a manufacturing method thereof, and a secondary battery using the electrode active material for a battery.

As a result of intensive studies, the present inventors have found that a new compound Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8) in a system in which calcium is added as a constituent element. And 0 ≦ z ≦ 5), and its chemical composition, crystal structure, and production method are clarified, and Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x <9). , 0 <y <1.8 and 0 ≦ z ≦ 5) were produced as a secondary battery, and an excellent initial discharge capacity and good cycle characteristics were confirmed. Thus, the present invention has been completed.

That is, this invention takes the structure of (1)-(6) shown below.
(1) As a general formula, Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) is taken, and sodium Manganese oxide characterized by containing calcium, manganese, titanium and oxygen as main components.
(2) As a general formula, Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) has a chemical composition, A manganese oxide having an orthorhombic crystal lattice and having a tunnel structure occupied by sodium and calcium ions of Na ₄ Mn ₄ Ti ₅ O ₁₈ type.
(3) Manganese oxidation having a chemical composition of Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) as a general formula Electrode active material for battery, including products.
(4) The method comprising a step of synthesizing by a high-temperature firing at 600 ° C. to 1300 ° C. in air using a compound composed of sodium, calcium, manganese, titanium, and oxygen as a starting material. Manufacturing method of manganese oxide.
(5) A process for synthesizing a battery electrode active material according to (3), comprising a step of synthesizing by a high-temperature firing at 600 ° C. to 1300 ° C. in air using a compound composed of sodium, calcium, manganese, titanium and oxygen as a starting material Production method.
(6) A secondary battery comprising two electrodes used as a positive electrode and a negative electrode and an electrolyte, wherein the battery active material according to (3) is used as a constituent member of the electrode.

According to the present invention, manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) can be produced. In addition, by using this manganese oxide as an active material for an electrode material, a secondary battery having excellent characteristics can be obtained.

The manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention is characterized by its crystal structure. As a compound having an orthorhombic crystal lattice and having a tunnel structure occupied by sodium and calcium ions of Na ₄ Mn ₄ Ti ₅ O ₁₈ type.
Furthermore, the new compound Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) is an electrode material for batteries. It can be used as an active material.

Among the present inventions, the production method of Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) includes sodium, calcium. And a compound composed of manganese, titanium, and oxygen as a starting material, and synthesized by high-temperature firing at 600 ° C. to 1300 ° C. in air.

In addition, an electrode containing Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention as an active material is provided. The alkaline secondary battery used as a constituent member is a secondary battery that has a high capacity and little deterioration associated with a charge / discharge cycle and can be expected to have a long life.

One-dimensional tunnel structure of manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention As shown in FIG. 1, a crystal structure having two types of tunnel spaces of different sizes by a skeletal structure constructed by connecting (Mn, Ti) O ₅ and (Mn, Ti) O ₆ polyhedra. It is characterized by being. Because of this crystal structure, it is possible to occlude a large amount of alkali ions in the tunnel, and since a one-dimensional conduction path is secured, the movement of ions in the tunnel direction is easy, and calcium Has the feature of stabilizing the tunnel structure.

  The production method according to the present invention will be described in more detail.

(Synthesis of manganese oxide)
Among the present invention, manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) is sodium as a raw material. At least one of the compounds, at least one of the calcium compounds, at least one of the manganese compounds, and at least one of the titanium compounds are weighed and mixed so that the ratio is freely selected within the above composition range, and air It can manufacture by heating in the atmosphere in which oxygen gas exists, such as inside.

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, and examples thereof include oxides such as Na ₂ O and NaNO ₃ , salts such as Na ₂ CO ₃ and NaNO ₃ , and hydroxides such as NaOH. It is done. Among these, Na ₂ CO ₃ is particularly preferable.

As the calcium raw material, at least one of calcium (metallic calcium) and a calcium compound is used. The calcium compound is not particularly limited as long as it contains calcium, and examples thereof include oxides such as CaO, salts such as CaCO ₃ and Ca (NO ₃ ) ₂ , and hydroxides such as Ca (OH) _2. Can be mentioned. Of these, CaCO ₃ is particularly 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 Mn ₃ O ₄ , Mn ₂ O ₃ and MnO ₂ , salts such as MnCO ₃ and MnCl ₂ , Mn (OH) Examples thereof include hydroxides such as ₂ and oxide hydroxides such as MnOOH. Among these, Mn ₂ O _{3 and the} like are particularly 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 . Of these, TiO ₂ is particularly preferable.

Alternatively, a composite compound composed of a plurality of constituent elements in advance among sodium, calcium, manganese, and titanium may be used as a raw material. For example, a sodium manganese complex compound, a sodium titanium complex compound, a manganese titanium complex compound, a calcium titanium complex compound, or the like can be used as a starting material. Specifically, complex oxides such as NaMnO ₂ , NaTiO ₂ , MnTiO ₃ and CaTiO ₃ , salts such as complex carbonates, complex acetates and complex oxalates, complex hydroxides and complex oxide hydroxides Etc. Among these, manganese titanium composite oxide hydroxide is particularly preferable.

First, a mixture containing these is prepared. The mixing ratio of the sodium raw material, the calcium raw material, and the manganese raw material is the Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5). It is desirable to mix with a chemical composition freely selected so as to be within the composition range of Moreover, since sodium easily volatilizes during heating and the amount of sodium in the product is often less than the charged composition, it is preferable to add the sodium amount in excess of several percent to several tens percent in mol%.

  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 set according to the composition of the mixture and the like, but is usually about 600 ° C to 1300 ° C, preferably 700 ° C to 1100 ° C. Also, the firing atmosphere is not particularly limited, and it may be usually carried out in an oxidizing atmosphere or an air atmosphere. The firing time can be appropriately changed according to the firing temperature. Although the cooling method is not particularly limited, usually, natural cooling (cooling in the furnace) or slow cooling may be performed.

  After firing, the fired product may be pulverized by a known method as necessary, and the above firing step may be further performed. That is, in the method of the present invention, it is preferable that the mixture is fired, cooled and pulverized at least once. Note that the degree of pulverization may be adjusted as appropriate according to the firing temperature and the like.

(Secondary battery)
The battery of the present invention contains a manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) active material The electrode to be used is used as a constituent member. That is, the active material Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention is used as one of electrode materials. Except for use, battery elements of known secondary batteries (coin type, button type, cylindrical type, all solid type, etc.) can be employed as they are.
FIG. 2 is a schematic view showing an example in which the secondary battery of the present invention is applied to a coin-type lithium secondary battery. The coin-type secondary 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 above-described Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) is necessary for the active material. In accordance with the above, an electrode mixture can be prepared by blending a conductive agent, a binder and the like, and an electrode can be produced by pressure-bonding it to a current collector. As the current collector, a stainless mesh, 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.

_{Na x Ca y Mn 9-z} Ti z O 18 in the electrode mixture material (composition range: 0 <x <9,0 <y <1.8, and 0 ≦ z ≦ 5) active material, conductor, binder, Although there is no particular limitation on the blending, etc., the conductive agent is usually about 1 to 30% by weight (preferably 5 to 25% by weight) and the binder is 0 to 30% by weight (preferably 3 to 10% by weight) And the remainder may be an active material of Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5). .

  In the secondary battery of the present invention, as the counter electrode with respect to the electrode, for example, a metal lithium, lithium alloy, metal sodium, or other known material that occludes lithium or sodium, or a carbon material that can occlude lithium is adopted. be able to.

  Moreover, what is necessary is just to employ | adopt a well-known battery element for a separator, a battery container, etc. in the battery of this invention.

  Furthermore, known electrolyte solutions, solid electrolytes, and the like can be applied as the electrolyte. For example, in the case of use as a lithium secondary battery, an electrolyte such as lithium perchlorate or lithium hexafluorophosphate is used as an electrolytic solution, such as ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC ), Those dissolved in a solvent such as diethyl carbonate (DEC) 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 Manganese Oxide Na _3.6 Ca _0.2 Mn ₉ O ₁₈ )
Sodium carbonate (Na ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), and manganese oxide (MnO ₂ ) were weighed so that the molar ratio of Na: Ca: Mn was 3.6: 0.2: 9. After mixing these uniformly in a mortar, the mixture was filled in an alumina crucible (JIS standard product SSA-S) and heated in air at 1000 ° C. for 10 hours using an electric furnace. Then, naturally allowed to cool in the electric furnace, by grinding the resulting fired body _was obtained new compound having a chemical composition comprising _{Na 3.6 Ca 0.2 Mn 9 O 18} .

It is clear that the obtained sample is a single phase of a tunnel structure belonging to the orthorhombic system and the space group Pbam having good crystallinity by an X-ray powder diffractometer (trade name RINT2500V, manufactured by Rigaku). became. The powder X-ray diffraction pattern of the obtained Na _3.6 Ca _0.2 Mn ₉ O ₁₈ is shown in FIG.

  Further, the particle morphology and chemical composition of the powder sample were examined with a scanning electron microscope (JEOL SEM-EDX, trade name JSM5400) with an energy dispersive elemental analyzer. As a result, the sample was composed of columnar primary particles with a length of about 1 to 5 μm, and calcium was detected from the chemical analysis spectrum of each particle, and it was confirmed that calcium could be uniformly substituted in the sample. It was done. FIG. 4 shows a scanning electron micrograph of the sample.

(Secondary battery)
The Na _3.6 Ca _0.2 Mn ₉ O ₁₈ thus obtained was used as an electrode active material, acetylene black as a conductive agent, and tetrafluoroethylene as a binder so that the weight ratio was 20: 5: 1. An electrode is prepared by mixing with lithium metal, and lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1: 1) using lithium metal as a counter electrode. A lithium secondary battery having the structure shown in FIG. 2 was prepared using the 1M solution as an electrolyte, and its charge / discharge characteristics were tested. The battery was produced according to a known cell configuration / assembly method.

  The manufactured lithium secondary battery was subjected to a charge / discharge test at a current density of 30 mA / g and a cut-off potential of 4.8-1.0 V under a temperature condition of 25 ° C., with an initial discharge capacity of about 80 mAh / g. , It has been found that it has a flat discharge portion in the vicinity of 3.0 V and can be reversibly charged and discharged. The voltage change accompanying charging / discharging is shown in FIG.

(Synthesis of Manganese Oxide Na _3.0 Ca _0.5 Mn ₉ O ₁₈ )
Sodium carbonate (Na ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), and manganese oxide (MnO ₂ ) were weighed so that the molar ratio of Na: Ca: Mn was 3.0: 0.5: 9. After mixing these uniformly in a mortar, the mixture was filled in an alumina crucible (JIS standard product SSA-S) and heated in air at 1000 ° C. for 10 hours using an electric furnace. Then, naturally allowed to cool in the electric furnace, by grinding a sintered body _obtained, to obtain a new compound having a chemical composition comprising _{Na 3.0 Ca 0.5 Mn 9 O 18} .

It is clear that the obtained sample is a single phase of a tunnel structure belonging to the orthorhombic system and the space group Pbam having good crystallinity by an X-ray powder diffractometer (trade name RINT2500V, manufactured by Rigaku). became. FIG. 6 shows the powder X-ray diffraction pattern of the obtained Na _3.0 Ca _0.5 Mn ₉ O ₁₈ .

  Further, the particle morphology and chemical composition of the powder sample were examined with a scanning electron microscope (JEOL SEM-EDX, trade name JSM5400) with an energy dispersive elemental analyzer. As a result, the sample was composed of columnar primary particles with a length of about 1 to 5 μm, and calcium was detected from the chemical analysis spectrum of each particle, and it was confirmed that calcium could be uniformly substituted in the sample. It was done. FIG. 7 shows a scanning electron micrograph of the sample. From the above, it was revealed that the manganese oxide of the present invention is a system having a composition range in the calcium substitution amount y.

The manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention is a one-dimensional tunnel. Due to the characteristics of the crystal structure that it has a structure, it has higher structural stability than the current spinel-type lithium manganese oxide, is advantageous for smooth occlusion / release of alkali ions such as lithium, and has charge / discharge cycle characteristics. It is an excellent material from the viewpoint. Therefore, it has high practical value as an electrode active material for secondary batteries such as lithium secondary batteries.

  Also, the manufacturing method does not require a special apparatus, and the raw material to be used is low in price, so that a high value-added material can be manufactured at a low cost.

Furthermore, the manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention is used as an active material. The secondary battery applied to the material is a secondary battery that has a high capacity and can be used for a long charge / discharge cycle.

Schematic showing the crystal structure of the manganese oxide Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) of the present invention. FIG. It is a schematic diagram which shows one example (coin-type lithium secondary battery) of a secondary battery. 2 is a powder X-ray diffraction pattern of the manganese oxide Na _3.6 Ca _0.2 Mn ₉ O ₁₈ of the present invention obtained in Example 1. FIG. 2 is a scanning electron micrograph showing the particle morphology of the manganese oxide Na _3.6 Ca _0.2 Mn ₉ O ₁₈ of the present invention obtained in Example 1. FIG. It is a figure which shows the charging / discharging characteristic of the secondary battery of this invention obtained in Example 1. FIG. 2 is a powder X-ray diffraction pattern of the manganese oxide Na _3.0 Ca _0.5 Mn ₉ O ₁₈ of the present invention obtained in Example 2. FIG. 4 is a scanning electron micrograph showing the particle morphology of the manganese oxide Na _3.0 Ca _0.5 Mn ₉ O ₁₈ of the present invention obtained in Example 2. FIG.

Explanation of symbols

a calcium b sodium 1 coin-type lithium secondary battery 2 negative electrode terminal 3 negative electrode 4 separator + electrolyte 5 insulating packing 6 positive electrode 7 positive electrode can

Claims (6)

As a general formula, Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8 and 0 ≦ z ≦ 5) is taken, and sodium, calcium, Manganese oxide characterized by containing manganese, titanium and oxygen as main components. While taking a chemical composition of Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8 and 0 ≦ z ≦ 5) as a general formula, orthorhombic crystal A manganese oxide having a crystal lattice of a system and having a tunnel structure occupied by sodium and calcium ions of Na ₄ Mn ₄ Ti ₅ O ₁₈ type. Including manganese oxide having a chemical composition of the general formula Na _x Ca _y Mn _9-z Ti _z O ₁₈ (composition range: 0 <x < _9, 0 <y <1.8, and 0 ≦ z ≦ 5) Battery electrode active material.   3. The manganese oxidation according to claim 1, comprising a step of synthesizing by a high-temperature firing at 600 ° C. to 1300 ° C. in air using a compound composed of sodium, calcium, manganese, titanium, and oxygen as a starting material. Manufacturing method.   The manufacturing method of the battery electrode active material of Claim 3 including the process of synthesize | combining by the high-temperature baking of 600 to 1300 degreeC in the air by using the compound comprised from sodium, calcium, manganese, titanium, and oxygen as a starting material.   The secondary battery which consists of two electrodes used as a positive electrode and a negative electrode, and electrolyte, Comprising: The secondary battery using the electrode active material for batteries of Claim 3 as a structural member of an electrode.