JP2004348983A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery using ion radical and/or O<SB>2</SB><SP>2-</SP>ion radical and/or O<SP>-</SP>ion radical as active oxygen species for a redox reaction. <P>SOLUTION: The secondary battery is provided with a positive electrode having a positive electrode active substance layer containing a compound expressed in a composition formula: Li<SB>y</SB>Ca<SB>12</SB>Al<SB>14-x</SB>Si<SB>x</SB>O<SB>33+x</SB>/<SB>2</SB>(provided, 0≤x≤4, 0≤y≤30) having a structure subsuming active oxygen species of O<SB>2</SB><SP>-</SP>, O<SB>2</SB><SP>2-</SP>, and O<SP>-</SP>in addition to O<SP>2-</SP>in high density in a skeleton structure, a negative electrode having a negative electrode active substance layer containing a compound expressed in a composition formula: Ca<SB>12</SB>Al<SB>14-x</SB>Si<SB>x</SB>O<SB>33+x</SB>/<SB>2</SB>(provided, 0≤x≤4) having a structure subsuming active oxygen species of O<SP>2-</SP>, O<SB>2</SB><SP>2-</SP>and O<SP>-</SP>in addition to O<SP>2-</SP>in high density in a skeleton structure, and nonaqueous electrolyte solution. This will be a 3V-class secondary battery in a battery system using an active substance material not containing transition metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reversible electrode material, a method for producing a reversible electrode using the same, and a secondary battery using the reversible electrode. More specifically, the present invention relates to a structure in which active oxygen species are included at a high concentration. Having the composition formula Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(Where 0 ≦ x ≦ 4) mayenite-like compound (hereinafter simply referred to as mayenite).
) As a new type of secondary battery using as an active material.
The present invention provides a new secondary battery based on a completely new basic principle utilizing the above mayenite as an active material in the field of secondary batteries, which are expected to spread and develop as large next-generation technologies following fuel cells. Useful as an offer.
[0002]
[Prior art]
Conventionally, with the miniaturization of personal computers, video cameras, mobile phones, and the like, in the field of information-related devices and communication devices, lithium-ion secondary batteries have been put into practical use as power supplies for these devices, and have become widespread. . In general, a lithium secondary battery generally includes a positive electrode using a lithium transition metal composite oxide as a positive electrode active material, a negative electrode using metal lithium, a carbon material, or the like as a negative electrode active material, and a lithium salt as a supporting salt. And an electrolytic solution dissolved in a solvent. This battery is a secondary battery that repeats a battery reaction in which lithium desorbed from the positive electrode is occluded in the negative electrode during charging, and lithium discharged from the negative electrode is occluded in the positive electrode during discharging, and lithium is used as a carrier. It is a rocking chair type secondary battery.
[0003]
In this lithium secondary battery, metallic lithium or a carbon material used as a negative electrode active material has a low reaction potential with lithium, and has a high operating voltage because a nonaqueous electrolytic solution is used as an electrolytic solution. It has the advantage of high energy density and is rapidly expanding its use as a power source for small portable devices. At present, as a positive electrode material of a lithium ion secondary battery, lithium cobalt oxide (LiCoO₂  ) Materials are used. However, since this lithium cobalt oxide contains cobalt, which is a rare metal, the use of this material is one of the factors of high material cost of the lithium secondary battery.
Therefore, for example, lithium manganese oxide (LiMn) is used as a cathode material that is inexpensive and has few resource problems.₂  O₄) Has attracted attention and has been partially commercialized. Furthermore, practical application of a positive electrode material using iron, which is a metal element that is more abundant, less toxic, and less expensive than manganese, is desired. For example, lithium ferrite (LiFeO)₂) Has been studied for its potential as an electrode material. However, lithium ferrite obtained by firing or hydrothermally treating an iron source such as iron oxide and a lithium source such as lithium carbonate at a high temperature hardly charges or discharges and has no activity as a lithium secondary battery. (For example, see Non-Patent Document 1).
[0004]
However, all of the above batteries use a change in the valence of a transition metal, and no other battery system utilizing a redox reaction has been found, and development thereof has been desired. The present inventors have sought a secondary battery using active oxygen for a redox reaction instead of a transition metal. Until now, there is no secondary battery using active oxygen for the redox reaction. The reason is that a favorable active material that can stably contain active oxygen in a crystal structure and that can reversibly occlude and desorb carriers such as lithium ions has not been found.
[0005]
[Non-patent document 1]
K. Ado, M .; Tabuchi, H .; Kobayashi, H .; Kageyama, O .; Nakamura, Y .; Inaba, R .; Kanno, M .; Takagi and Y. Takeda, J .; Electochem. Soc. , 144, [7], L177, (1997)
[0006]
[Problems to be solved by the invention]
Under such circumstances, the present inventors have conducted intensive studies and studies with the aim of developing a new type of secondary battery using a new active material instead of a transition metal in view of the above-mentioned problems of the prior art. As a result of repeated experiments, we gained the knowledge that some of the mayenite-like composite oxides contained active oxygen in their crystal structures and could be an active material capable of absorbing and desorbing lithium. As a result, the composition formula Ca containing the active oxygen species in the crystal₁₂Al_14-xSi_xO_{33 + x / 2}(However, the mayenite-like compound represented by 0 ≦ x ≦ 4) has a property that lithium is inserted at 0.5 V or less and desorbed at 3.5 V, and the present invention has been completed.
That is, an object of the present invention is to provide a new battery configuration capable of forming a new concept secondary battery using active oxygen for the Redox reaction.
Another object of the present invention is to provide a novel secondary battery formed using the active material.
[0007]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems includes the following technical means.
(1) O in the skeleton structure^2-Besides O₂ ⁻And O₂ ^2-  And O⁻A secondary battery characterized in that an oxide having a structure in which active oxygen species are included in a high concentration is used as an active material, and a redox reaction is carried out by these active oxygen.
(2) Composition formula Li_y  Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(Where 0 ≦ x ≦ 4, 0 ≦ y ≦ 30) and a positive electrode having a positive electrode active material layer containing a compound represented by the following formula:^2-Besides O₂ ⁻And O₂ ^2-  And O⁻Having a structure in which a high concentration of active oxygen species is included in Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(2) The secondary battery according to the above (1), comprising a negative electrode having a negative electrode active material layer containing a compound represented by (0 ≦ x ≦ 4) and a non-aqueous electrolyte.
(3) Composition formula Ca₁₂Al_14-xSi_x  O_{33 + x / 2}Wherein lithium is electrochemically inserted into a compound represented by the formula (0 ≦ x ≦ 4) using a lithium compound soluble in a non-aqueous organic solvent as a supporting salt._y  Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(Provided that 0 ≦ x ≦ 4, 0 ≦ y ≦ 30).
(4) Composition formula Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(0 ≦ x ≦ 4) and a lithium compound, and further heat-treating at 300 ° C. to 800 ° C. in the air, an oxidizing atmosphere or a reducing atmosphere, and then removing the remaining lithium compound by a solvent washing treatment. Formula Li_y  Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(Provided that 0 ≦ x ≦ 4, 0 ≦ y ≦ 30).
(5) Composition formula Li_y  Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(Where 0 ≦ x ≦ 4, 0 ≦ y ≦ 30), for a lithium-ion secondary battery comprising a Li—Ca—Al—Si-based oxide having a cubic structure. Positive electrode material.
(6) Composition formula Ca₁₂Al_14-xSi_x  O_{33 + x / 2}A negative electrode material for a lithium ion secondary battery, represented by the formula (0 ≦ x ≦ 4) and comprising a Ca—Al—Si-based oxide having a cubic structure.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail.
The present invention relates to a method for preparing O^2-Besides O₂ ⁻  And O₂ ^2-  And O⁻  A secondary battery characterized in that an oxide having a structure in which active oxygen species are included in a high concentration is used as an active material, and a redox reaction is carried out by these active oxygens. Composition formula Ca containing seed in crystal₁₂Al_14-xSi_x  O_{33 + x / 2}(Where 0 ≦ x ≦ 4) is a secondary battery using a mayenite-like compound represented by the formula: Li_y  Ca₁₂Al_14-xSi_x  O_{33 + x / 2}(Where 0 ≦ x ≦ 4, 0 ≦ y ≦ 30), a positive electrode having a positive electrode active material layer containing a lithium-containing mayenite-like compound, and the above-mentioned mayenite-like compound (composition formula Ca₁₂Al_14-xSi_x  O_{33 + x / 2}The present invention relates to a secondary battery including a negative electrode having a negative electrode active material layer containing (0 ≦ x ≦ 4) and a non-aqueous electrolyte.
[0009]
In the present invention, mayenite is preferably produced, for example, as follows. In the present specification, “mayenite” is defined as meaning a mayenite-like compound having the above composition formula.
(1) Production of mayenite
(A) Mayenite
In the present invention, mayenite is hydrogarnet (Ca₃Al₂  (SiO₄  )_3-x  (OH)_4x(Where 0 ≦ x ≦ 3)) at 300 ° C. to 1100 ° C. in air or oxygen. Hydrogarnet, which is a precursor of mayenite, includes, for example, a silica source (kaolin, silica, amorphous silica, diatomaceous earth, silica sand, quartz, etc.) and an alumina source (kaolin, alumina sol, boehmite, aluminum hydroxide, aluminum oxide, etc.). Etc.) and a mixture of a calcium source (eg, slaked lime, quicklime, gypsum, etc.) or a mixture of the above-mentioned alumina source and a calcium source in a temperature range of 80 ° C. to 200 ° C. by hydrothermal treatment. In this case, when hydrogarnet is manufactured at a temperature of 80 ° C. or less, there is a problem that the reaction rate is low and the crystallinity of the obtained material is low. In this case, the pressure in the container becomes high, and a special container is required, which is not industrial.
[0010]
(B) Mayenite loaded with a transition metal or noble metal oxide
The hydrogarnet powder is mixed and stirred with an aqueous solution of a nitrate or acetate of a transition metal or a noble metal, then evaporated to dryness on a hot plate at 110 ° C., and further heated at 600 ° C. or more for 3 hours. Thus, a hydrogarnet carrying an oxide of a transition metal or a noble metal is obtained. By firing this at 800 ° C. to 1100 ° C. in air or oxygen, mayenite can be produced.
[0011]
(C) Transition metal or noble metal substituted mayenite
1) Production of chromium-substituted mayenite
Calcium nitrate tetrahydrate is added to distilled water, and chromium nitrate nonahydrate, amorphous silica powder and aluminum hydroxide are mixed (so that the pH becomes 13 or more by adding an aqueous sodium hydroxide solution). adjust). This mixture was put in an autoclave, kept at 200 ° C. for 3 days, cooled, taken out of the sample, filtered and dried to obtain a chromium-substituted hydrogarnet powder. This can be manufactured by firing at 400 ° C. for 10 hours in air or oxygen.
[0012]
2) Production of iron-substituted mayenite
Calcium oxide is added to distilled water, aluminum hydroxide and amorphous silica powder are mixed with the suspension, and iron nitrate nonahydrate is further mixed (an aqueous solution of sodium hydroxide is added to adjust pH = 13). Adjust so that it is above). The mixture is put in an autoclave, kept at 200 ° C. for 3 days, cooled, taken out of the sample, filtered and dried to obtain iron-substituted hydrogarnet powder. This can be manufactured by firing at 400 ° C. for 10 hours in air or oxygen. In addition, mayenite produced by the above production method may contain a small amount of calcium oxide during conversion from hydrogarnet, but in the present invention, these impurity phases are contained within a range that does not significantly affect the charge / discharge characteristics. May be included.
[0013]
(2) Production of lithium-containing mayenite
In the present invention, as a method for producing lithium-containing mayenite, a known ceramic synthesis method such as an electrochemical reaction method, a firing method, or a hydrothermal reaction method can be preferably used. Hereinafter, first, production by an electrochemical reaction method will be illustrated, and then, as an example of a known ceramic synthesis method, a production method by a firing method will be described. However, it is not limited to the following method.
[0014]
(A) Production of lithium-containing mayenite by electrochemical reaction method
The production of lithium-containing mayenite by an electrochemical reaction method is characterized in that the mayenite described in the above (1) is opposed to lithium metal via a separator and electrode-oxidized in, for example, an organic solvent containing a Li salt. Specifically, in the present invention, a conductive material and a binder are mixed with a mayenite powder to prepare a paste-like mixture, and for example, the mixture is applied to the surface of a metal foil current collector. Then, an electrode is produced, and the electrode is oxidized in a container in which this electrode and a lithium metal are provided facing the electrode. The conductive material is for ensuring the electrical conductivity of the positive electrode, and is preferably, for example, a material obtained by mixing one or more of carbon material powders such as carbon black, acetylene black, and graphite. Can be used. The binder plays a role of binding the active material particles and the conductive material particles, and is preferably, for example, a fluorine-containing resin such as Teflon (registered trademark), polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber. And thermoplastic resins such as polypropylene and polyethylene.
[0015]
The positive electrode mixture can also be prepared by adding a solvent for the purpose of viscosity adjustment or the like, depending on the convenience of coating, and in that case, an organic solvent such as N-methyl-2-pyrrolidone may be used. Can be. As the current collector, it is desirable to use a substance which is electrochemically stable to the positive electrode reaction, and preferably, for example, aluminum or the like can be used. The positive electrode formed by coating the metal foil current collector is sheet-shaped, but the sheet-shaped positive electrode can have various thicknesses depending on the shape of the battery to be manufactured. In addition, various sizes can be obtained by means such as cutting. If necessary, a material pressed by a means such as a press may be used to increase the density of the positive electrode mixture.
[0016]
(B) Production of lithium-containing mayenite by firing method
In the production of the lithium-containing mayenite by the firing method, the mayenite described in the above (1) is dispersed in distilled water or a mixed solution of water-alcohol (for example, ethanol and methanol), and a lithium compound such as lithium hydroxide is dispersed therein. , And the molar ratio (Li / Ca) of lithium to other metal amounts is about 1 to 3; the resulting solution and precipitate are evaporated to dryness; the resulting residue is fired in an oxidizing atmosphere. It is characterized by doing.
[0017]
Examples of the lithium compound used in the above firing method include water-soluble compounds such as chlorides, nitrates, sulfates, acetates, and hydroxides of these metals. Alternatively, these metal source materials may be either anhydrous or hydrated. Each water-soluble compound may be used alone or in combination of two or more. In the firing method, it is necessary to adjust the molar ratio (Li / Ca) of the charged lithium amount to the other metal amount, and the value is usually about 1 to 3, preferably about 1.5 to 2.5. If it is less than 1.5, a desired composition of lithium-containing mayenite may not be obtained, and if it is more than 2.5, there is a problem that mayenite is decomposed to form a lithium-aluminum composite oxide. .
[0018]
As an atmosphere for performing the firing, for example, an oxidizing atmosphere such as air or a reducing atmosphere such as hydrogen can be exemplified. The firing temperature is usually about 200C to 1000C. If the temperature is lower than 300 ° C., the reaction may not proceed sufficiently, and if the temperature is higher than 800 ° C., the mayenite structure may be decomposed.
The firing time is about 1 to 100 hours, and if it is 5 hours or less, the reaction may be insufficient, and if it is 100 hours, there is a problem that crystals grow, the material has a small surface area and the electrode reaction is slow, and it is preferable. Is about 5 to 20 hours. After firing, if necessary, the product may be pulverized, and firing may be repeated under the same conditions as described above. When the above-mentioned calcination method is used, not only a mayenate containing 50% or more of lithium can be obtained, but also a mayenite doped with lithium in an amount of less than 50% can be obtained.
[0019]
(3) Li secondary battery
The lithium secondary battery of the present invention is a lithium secondary battery using the above-described lithium-containing mayenite as a positive electrode active material and mayenite as a negative electrode active material, and is a rocking chair type secondary battery using lithium as a carrier. The main components of the configuration are a positive electrode using the above-mentioned lithium-containing mayenite as an active material, a negative electrode using mayenite as an active material, and an electrolytic solution.
[0020]
(A) Positive electrode
The electrode manufactured by the method described in the above (2)-(a) can be used as it is as a positive electrode. In the case of the lithium-containing mayenite synthesized by the production method described in the above (2)-(b), a conductive material and a binder are mixed with this powder to prepare a paste-like positive electrode mixture. The positive electrode mixture can be applied to the surface of the metal foil current collector to form an electrode. The conductive material is for ensuring the electrical conductivity of the positive electrode, and is preferably, for example, a material obtained by mixing one or more of carbon material powders such as carbon black, acetylene black, and graphite. Can be used. The binder plays a role of binding the active material particles and the conductive material particles, and is preferably, for example, a fluorine-containing resin such as Teflon (registered trademark), polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber. And thermoplastic resins such as polypropylene and polyethylene.
[0021]
The positive electrode mixture can also be prepared by adding a solvent for the purpose of viscosity adjustment or the like depending on the convenience at the time of coating, and in that case, for example, an organic solvent such as N-methyl-2-pyrrolidone is used. Can be used. As the current collector, it is desirable to use a substance that is electrochemically stable to the positive electrode reaction, and for example, aluminum or the like can be used.
The positive electrode formed by coating the metal foil current collector has a sheet shape, and the sheet-shaped positive electrode can have various thicknesses depending on the shape of the battery to be manufactured. Also, it can be made into various sizes by means such as cutting. If necessary, a material pressed by a means such as a press may be used to increase the density of the positive electrode mixture.
[0022]
(B) negative electrode
The negative electrode is prepared by mixing a conductive material and a binder into the above-mentioned mayenite powder to be a negative electrode active material to prepare a paste-like negative electrode mixture. Can be formed by coating. The conductive material is for ensuring the electrical conductivity of the negative electrode. For example, preferably, one or a mixture of two or more kinds of powdered carbon materials such as carbon black, acetylene black, and graphite is used. Can be used. The binder plays a role of binding the active material particles and the conductive material particles, and is preferably, for example, a fluorine-containing resin such as Teflon (registered trademark), polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber. And thermoplastic resins such as polypropylene and polyethylene. The negative electrode mixture can also be prepared by adding a solvent for the purpose of viscosity adjustment or the like, depending on the convenience of coating, and in this case, for example, an organic solvent such as N-methyl-2-pyrrolidone is used. Can be used. As the current collector, it is desirable to use a substance which is electrochemically stable to the negative electrode reaction, and for example, copper or the like can be used. The negative electrode formed by coating on the metal foil current collector has a sheet shape, and the sheet-shaped negative electrode can have various thicknesses depending on the shape of the battery to be manufactured. Also, it can be made into various sizes by means such as cutting. If necessary, a material pressed by a means such as a press may be used to increase the density of the negative electrode mixture.
[0023]
(C) Electrolyte
The electrolytic solution is a liquid containing lithium as a carrier in an ionic state, and is obtained by dissolving a lithium salt as a supporting salt in a solvent. In the lithium secondary battery of the present invention, the battery can be constituted by either a non-aqueous electrolyte using an organic solvent or an aqueous electrolyte using water as a solvent. When a non-aqueous electrolyte is used, as a lithium salt serving as a supporting salt, for example, LiBF₄  , LiPF₆  , LiClO₄  , LiCF₃  SO₃  , LiAsF₆  Etc. can be used. As the organic solvent, an aprotic organic solvent can be used. For example, a mixed solvent of one or more of cyclic carbonate, chain carbonate, cyclic ester, cyclic ether or chain ether is used. be able to. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate.
[0024]
Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.Examples of the cyclic ester include gamma butyrolactone and gamma valerolactone.Examples of the cyclic ether include tetrahydrofuran and 2-methyl Examples of chain ethers include tetrahydrofuran and the like, and dimethoxyethane, ethylene glycol dimethyl ether, and the like, respectively. Among these, any one type can be used alone, or two or more types can be mixed and used. The supporting salt concentration in the non-aqueous electrolyte is desirably 0.8 to 1.5M. This is because at a concentration of 0.8 M or less, the lithium ion conductivity is low, and at a concentration of 1.5 M or more, the supporting salt becomes supersaturated, and the supporting salt precipitates in the solvent to adversely affect battery characteristics. .
[0025]
(D) Other components
The lithium secondary battery of the present invention may be manufactured by forming an electrode body with the above-described positive electrode and the above-mentioned negative electrode facing each other, and inserting this electrode body into a battery case together with an electrolytic solution in a container. When facing the positive electrode and the negative electrode, a separator is interposed between the two. The separator separates the positive electrode and the negative electrode and holds the electrolytic solution.When a non-aqueous electrolytic solution is used, preferably, for example, a thin microporous film of polyethylene, polypropylene, or the like, a nonwoven fabric, paper, or the like is used. In the case of an aqueous electrolyte, for example, a nonwoven fabric, paper, or the like can be used. In addition, the shape and size of the lithium secondary battery of the present invention are not particularly limited, and may be various types such as a cylindrical type, a stacked type, a coin type, and a card type.
[0026]
An appropriate battery case may be used according to the shape of the battery to be manufactured. The battery case may be provided with a positive electrode external terminal and a negative electrode external terminal, and a part of the battery case may be of a type which also serves as a positive electrode external terminal and a negative electrode external terminal. Regardless of which shape, type, etc. is adopted, the above-mentioned electrode body is housed in a battery case, and electrically connected between the positive electrode and the negative electrode to the positive electrode external terminal and the negative electrode external terminal respectively, and the electrolytic solution is discharged. The lithium secondary battery is completed by injecting the battery, sealing the battery case and separating the battery system from the outside.
As described above, the lithium secondary battery of the present invention and the method of manufacturing the same have been described. However, the above-described embodiment is merely an embodiment of the present invention. It goes without saying that the present invention can be implemented in various forms based on the embodiments and various modifications and improvements based on the knowledge of those skilled in the art.
[0027]
【Example】
Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.
In the following examples, lithium-containing mayenite and mayenite were manufactured, and a positive electrode active material and a negative electrode active material were used to produce a lithium secondary battery, and a charge / discharge test was performed on the secondary battery. Thereby, the secondary battery was evaluated.
[0028]
(1) Example 1
(A) Production of mayenite
0.84 g of aluminum oxide, 0.39 g of amorphous silica, and 60 ml of distilled water were mixed with 1.39 g of calcium oxide. The suspension thus prepared was placed in an autoclave having a total volume of 100 ml, kept at 200 ° C. for 10 hours while stirring (30 rpm), cooled to room temperature, taken out of the sample, filtered, and dried to obtain a hydrogarnet powder. Obtained. The thus obtained hydrogarnet was fired at 800 ° C. in air to produce mayenite.
[0029]
(B) Production of lithium-containing mayenite
70 parts by weight of the mayenite produced in (a) above were mixed with 25 parts by weight of Ketjen black as a conductive material and 5 parts by weight of Teflon (registered trademark) as a binder to prepare a mixture. Was press-formed on the surface of an aluminum foil current collector having a thickness of 22 μm to prepare a sheet having a thickness of the positive electrode mixture of 50 μm, and then a disk-shaped electrode formed by punching the sheet into a diameter of 15 mmφ. . A metal lithium having a thickness of 0.1 mm and a diameter of 15 mm was opposed to the electrode, and a non-woven fabric having a thickness of 100 μm was used as a separator sandwiched between the electrode and the electrode. The electrolyte solution is 1 M LiPF₆  Was dissolved in a solvent in which EC (ethylene carbonate) and DEC (diethyl carbonate) were mixed at a volume ratio of 3: 7. A cell in which these are sandwiched between Teflon (registered trademark) plates is produced, and 0.1 mA / cm up to 4.5 V.²  And then washed with DEC (diethyl carbonate) to produce lithium-containing mayenite.
[0030]
(C) Production of lithium secondary battery
A lithium secondary battery was manufactured using the lithium-containing mayenite of (b) above as a positive electrode active material and the mayenite of (a) above as a negative electrode active material. The electrodes described in the above (2) to (a) were used as the positive electrode. Mayenite was used for the negative electrode facing the positive electrode. 70 parts by weight of mayenite, 25 parts by weight of Ketjen black as a conductive material and 5 parts by weight of Teflon (registered trademark) as a binder were mixed to prepare a mixture, and the mixture was mixed with a copper foil having a thickness of 22 μm. A sheet in which the thickness of the positive electrode mixture was 50 μm was produced by pressure molding on the surface of the current collector. A nonwoven fabric having a thickness of 100 μm was used for the separator sandwiched between the positive electrode and the negative electrode. The lithium secondary battery was completed by incorporating the above-described positive electrode, negative electrode, and separator into a coin-type battery case (2016 type), impregnating the electrolyte, and then sealing the battery case. In addition, what melt | dissolved 1 M LiPF6 in the solvent which mixed EC (ethylene carbonate) and DEC (diethyl carbonate) at a volume ratio of 3: 7 was used for the electrolytic solution.
[0031]
(2) Example 2
(A) Production of iron-substituted mayenite
1.6 g of aluminum hydroxide and 0.65 g of amorphous silica powder were added to a suspension obtained by stirring 22 ml of distilled water and 1.8 g of calcium oxide, followed by stirring and mixing. To this, 0.55 g of iron nitrate nonahydrate and 30 ml of distilled water were added, and sufficiently stirred and mixed. Thereafter, 30 ml of a 3N aqueous sodium hydroxide solution was added to adjust the pH of the solution to 13 or more. The suspension thus prepared was put in an autoclave having a total volume of 100 ml, kept at 200 ° C. for 3 days while stirring (30 rpm), washed with water and dried to obtain a hydrogarnet powder. The obtained hydrogarnet was fired in air at 800 ° C. to produce iron-substituted mayenite.
[0032]
(B) Production of lithium-containing iron-substituted mayenite
A mixture was prepared by mixing 70 parts by weight of the iron-substituted mayenite produced in (a) above with 25 parts by weight of Ketjen black as a conductive material and 5 parts by weight of Teflon (registered trademark) as a binder. The mixture was pressure-formed on the surface of an aluminum foil current collector having a thickness of 22 μm to form a sheet in which the thickness of the positive electrode mixture was 50 μm. Then, a disk-shaped electrode obtained by punching this sheet into a diameter of 15 mmφ was used. Produced. A metal lithium having a thickness of 0.1 mm and a diameter of 15 mm was opposed to the electrode, and a non-woven fabric having a thickness of 100 μm was used as a separator sandwiched between the electrode and the electrode. The electrolyte is 1M LiPF₆  Was dissolved in a solvent in which EC (ethylene carbonate) and DEC (diethyl carbonate) were mixed at a volume ratio of 3: 7. A cell in which these were sandwiched between Teflon (registered trademark) plates was prepared, and 0.1 mA / cm up to 4.5 V.²  And then washed with DEC (diethyl carbonate) to produce lithium-containing iron-substituted mayenite.
[0033]
(C) Production of lithium secondary battery
A lithium secondary battery was manufactured in the same manner as in Example 1, except that lithium-containing iron-substituted mayenite was used as the positive electrode active material.
[0034]
(3) Example 3
(Charge / discharge test and evaluation of lithium secondary battery)
A charge / discharge test was performed on the lithium secondary battery. The charge / discharge test was conducted at a current density of 0.25 mA / cm up to a charge end voltage of 3.0 V.²  And a current density of 0.25 mA / cm up to a discharge end voltage of 0.2 V.²  The charge / discharge cycle of discharging at a constant current is repeated. As a result of the charge / discharge test, FIG. 1 shows a charge / discharge curve of the lithium secondary battery manufactured in Example 1 in the first cycle (a curve showing a relationship between battery terminal voltage and capacity per positive electrode active material). Is shown. As can be seen from the charge / discharge curve, the charge capacity was 293 mAh / g, and the discharge capacity was 256 mAh / g. Although not shown, the capacity after the second cycle was substantially the same as that of the first cycle. Judging from these results, it was concluded that in the lithium secondary battery of the present invention, a secondary battery capable of reversibly charging and discharging a considerable capacity can be constituted by using an active material containing no transition metal. Can be The lithium secondary battery manufactured in this example is a completely new type rocking chair type secondary battery in which active oxygen contained in the crystal structure of mayenite is redox.
[0035]
【The invention's effect】
As described in detail above, the present invention relates to a secondary battery using a mayenite-like compound as an active material, and the secondary battery of the present invention includes active oxygen as described above in a crystal structure. Using this as a redox, reversible insertion and extraction of lithium is possible, and a rocking chair type secondary battery using lithium as a carrier can be realized. Further, since the lithium secondary battery does not include an expensive transition metal in the active material, a significant reduction in manufacturing cost can be expected. Further, since the main component of the active material is composed of oxides of calcium, aluminum, and silicon, there is an effect that there is no need to collect the battery.
[Brief description of the drawings]
FIG. 1 shows a charge / discharge curve at the first cycle of a secondary battery manufactured in an example.

Claims (6)

An oxide having a structure in which active oxygen species such as O ₂ ⁻ or O ₂ ²⁻ or O ⁻ in addition to O ²⁻ are included in the skeleton structure in a high concentration is used as an active material, and a redox reaction is performed for these activities. A secondary battery characterized by being carried by oxygen. Compositional formula _{Li y Ca 12 Al 14-x} Si x O 33 + x / 2 ( provided that 0 ≦ x ≦ 4,0 ≦ y ≦ 30) a positive electrode having a positive electrode active material layer containing a compound represented by, _{O 2} in addition to ^{O 2-} on the backbone structure ^- or _O ^{2 2-or} O ^- composition formula having a hull contact structure active oxygen species to high concentrations of _{Ca 12 Al 14-x Si x} O 33 + x / 2 ( The secondary battery according to claim 1, comprising a negative electrode having a negative electrode active material layer containing a compound represented by 0 ≦ x ≦ 4) and a non-aqueous electrolyte. To the compound represented by the composition formula _{Ca 12 Al 14-x Si x} O 33 + x / 2 ( provided that 0 ≦ x ≦ 4), as a supporting salt soluble lithium compound in a non-aqueous organic solvent, an electrochemically lithium compositional formula _{Li y Ca 12 Al 14-x} Si x O 33 + x / 2 , wherein the insert (where, 0 ≦ x ≦ 4,0 ≦ y ≦ 30 at a) manufacturing method of the compound represented by. Composition formula _{Ca 12 Al 14-x Si x} O 33 + x / 2 ( provided that 0 ≦ x ≦ 4) and added lithium compound, further in the atmosphere after heat-treated at 300 ° C. to 800 ° C. in an oxidizing atmosphere or a reducing atmosphere, the solvent Table a composition and removing the lithium compound remaining formula _{Li y Ca 12 Al 14-x} Si x O 33 + x / 2 ( provided that 0 ≦ x ≦ 4,0 ≦ y ≦ 30) by the cleaning process For producing a compound to be prepared. Compositional formula _{Li y Ca 12 Al 14-x} Si x O 33 + x / 2 ( provided that, 0 ≦ x ≦ 4,0 ≦ y ≦ 30) is represented by, Li-Ca-Al-Si having a cubic structure A positive electrode material for a lithium ion secondary battery, comprising a system oxide. Expressed by a composition formula _{Ca 12 Al 14-x Si x} O 33 + x / 2 ( provided that 0 ≦ x ≦ 4), lithium-ion secondary characterized in that it consists of Ca-Al-Si-based oxide having a cubic structure Anode material for secondary battery.

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