JP5643182B2 - Lithium-air secondary battery and method for producing air electrode thereof - Google Patents

Description

  The present invention relates to a lithium air secondary battery having a low charging voltage and excellent cycle characteristics.

  Metal-air batteries have a theoretical energy density that far surpasses lithium-based batteries such as lithium ion batteries. Among these, zinc-air primary batteries have a large discharge capacity of about 300 mAh / g, and are mainly used for hearing aids and the like. However, since only a voltage of about 1 V can be obtained as compared with a lithium battery using a non-aqueous electrolyte, it is considered difficult to use widely.

  In recent years, electrochemical reduction (discharge) / generation (charge) of oxygen is used as the positive electrode reaction system in the same manner as zinc-air batteries, and lithium is combined with zinc as the negative electrode, and non-aqueous as the electrolyte. Attempts to produce a lithium-air secondary battery exhibiting a high voltage of 2 to 3 V have been made by using an electrolyte, and a large discharge capacity of 1000 mAh / g or more has been obtained in the first discharge.

  However, if the cycle is repeated due to the fact that the voltage at the time of charging is as high as 4 V or more, decomposition of the electrolyte occurs, and the reversibility of deposition and decomposition of the discharge product (lithium oxide) is insufficient. There is a problem that the capacity is significantly reduced. Therefore, attempts have been made to increase the activity of the electrode by adding a catalyst to the positive electrode for the lithium-air secondary battery.

In Non-Patent Document 1, a lithium-air secondary battery using a positive electrode to which Pt or various metal oxides are added as a catalyst is manufactured and a charge / discharge test is performed. When MnO ₂ is added as a metal oxide catalyst, the initial discharge capacity is 1000 mAh / g, indicating a capacity of 600 mAh / g even after 50 cycles. In addition, when Fe ₂ O ₃ is added, the initial discharge capacity is 2700 mAh / g, and after 10 cycles, 75 mAh / g, and when Fe ₃ O ₄ is added, the initial discharge capacity is about 1200 mAh / g, after 10 cycles. A capacity of 800 mAh / g is shown. However, the capacity reduction due to the cycle is remarkable, and it is considered that further improvement of the cycle characteristics is necessary for practical use as a secondary battery.

An O2 cathode for rechargeable lithium batteries: The effect of a catalyst '', A. Debart, J. Bao, G. Armstrong, P. G. Bruce, Journal of Power Sources, Vol. 174, P. 1177-1182 (2007).

  As described above, the conventional lithium-air secondary battery has a problem that the charging voltage is high and the cycle is difficult.

  The purpose of the present invention is to promote the decomposition of precipitates generated during discharge by mixing a highly active catalyst with the positive electrode, which is considered to be important for reducing the charging voltage of the lithium air secondary battery, and is very excellent. A lithium-air secondary battery having cycle characteristics is provided.

In order to solve the above-mentioned problem, the invention of the lithium air secondary battery according to claim 1 of the present invention comprises a positive electrode comprising carbon, a catalyst and a binder, and a substance capable of occluding and releasing metallic lithium or lithium ions. Lithium air comprising a non-aqueous or aqueous electrolyte solution arranged between the positive electrode and the negative electrode so that one surface of the positive electrode is in contact with air and the other surface is in contact with the non-aqueous electrolyte. In the battery, a brown millerite oxide (A ₂ B ₂ O ₅ ) is mixed as the positive electrode catalyst.

  The invention according to claim 2 of the present invention is the brown millerite type produced by using at least one of A = Ca, Sr, B = Mn and Fe as the brown millerite type oxide. An oxide is mixed with the positive electrode.

The invention according to claim 3 of the present invention is the brown millelite in which A = Ca, B = Mn is used as the brown millelite type oxide, and a part of the Mn is replaced with Fe, Co, Ni. A light-type oxide (Ca ₂ Mn _2−x M _x O ₅ , M = Fe, Co, Ni) is mixed with the positive electrode.

In the invention according to claim 4 of the present invention, the crystallite diameter of the brown millerite type oxide is 400 to 500 mm, and the specific surface area determined by the BET method by N ₂ adsorption is 40 to 50 m. It is characterized in that a brown millerite type oxide of ² / g is mixed with the positive electrode.

In order to solve the above-mentioned problem, a method for producing a lithium-air secondary battery according to claim 5 of the present invention includes a step of producing a positive electrode by mixing carbon, a catalyst, and a binder, and metallic lithium or lithium. A step of producing a negative electrode using a substance capable of occluding and releasing ions; and between the positive electrode and the negative electrode so that one surface of the positive electrode is in contact with air and the other surface is in contact with a non-aqueous electrolyte. A step of disposing a non-aqueous or aqueous electrolyte solution, wherein the catalyst of the positive electrode is mixed with a brown millerite oxide (A ₂ B ₂ O ₅ ).

  According to the present invention, by mixing a highly active catalyst with the positive electrode, good reversibility of the discharge product can be obtained, and the charging voltage is lowered, so that a lithium air secondary battery having excellent cycle characteristics is provided. can do.

It is the figure which showed the XRD pattern of the brown millerite type oxide which is an oxide catalyst of the lithium air secondary battery which concerns on this invention. It is sectional drawing of the lithium air battery cell of the lithium air secondary battery which concerns on this invention. It is a figure which shows the discharge curve of the lithium air secondary battery by Examples 1-7 of this invention, and the comparative example 1. FIG. It is a figure shown with the discharge curve of the lithium air secondary battery by Examples 7-9 and Comparative Example 2 of this invention. It is a table | surface which shows the discharge capacity of the lithium air secondary battery by Example 1-9 of this invention, and the comparative example 1 and 2, the crystallite diameter of manganese oxide, and a specific surface area.

  An outline of the lithium air secondary battery according to the present invention will be described.

The positive electrode of the lithium-air secondary battery according to the present invention is composed of carbon, a catalyst, and a binder in order to advance an electrochemical redox reaction of oxygen, which is a positive electrode active material, and includes carbon powder, catalyst powder, and polytetrafluoroethylene. A mixture with a binder powder such as (PTFE) is pressure-molded on a support such as a breathable metal mesh, or the above mixture is dispersed in a solvent such as an organic solvent to form a slurry. It is produced using means such as coating on a metal mesh and drying. One side of the produced positive electrode is exposed to the atmosphere, and the other side is in contact with the electrolyte. Moreover, in order to increase the strength of the electrode and prevent leakage of the electrolytic solution, it is possible to produce an electrode having more excellent stability by performing not only cold pressing but also hot pressing. Here, the discharge reaction on the positive electrode can be expressed by the following equation.
2Li ⁺ + O ₂ + 2e ⁻ → Li ₂ O ₂ (1) or 2Li ⁺ + 1 / 2O ₂ + 2e ⁻ → Li ₂ O (2)

The lithium ions in the above formula have moved from the negative electrode to the positive electrode surface via the electrolyte. Further, oxygen is taken into the positive electrode from the atmosphere. The discharge reaction Li ₂ O ₂ generated by, or, Li ₂ O is deposited on the positive electrode, discharge reaction at the time when all the positive electrode reaction sites coating is completed. At the time of charging, a reaction opposite to the discharge reaction occurs, and the charging reaction is completed when all the discharge products generated at the time of decomposition are decomposed.

  As the carbon as the positive electrode material, ketjen black, acetylene black, activated carbon, carbon fiber, etc. can be used, but the crystal is not grown, the particle size is small, and there are many reaction sites. It is desirable to use surface area carbon.

As the catalyst as the positive electrode material, a noble metal, a transition metal, or an oxide thereof can be used, but a catalyst material having no crystallite grown, a small particle size, and a high surface area is used. It is desirable. As a result of intensive studies on the charge / discharge characteristics of a lithium-air secondary battery produced using a positive electrode mixed with a metal composite oxide as the catalyst, the inventors have found that the brown millerite oxide A ₂ B ₂ O It has been found that when ₅ is mixed with the positive electrode as a catalyst, the charging voltage is lowered and the cycle characteristics are improved. It has been found that excellent properties can be obtained by using a brown millelite type oxide obtained when A = Ca, Sr, B = Mn, Fe, Co, and Ni.

Further, the inventors of the present invention, as the catalyst material, particularly when A = Ca and B = Mn, Brown Millerite type oxide (Ca ₂ Mn _2-x M) in which a part of Mn is substituted with Fe, Co, and Ni. _{x O 5, M = Fe,} Co, was found to exhibit more excellent characteristics by using a Ni).

Further, the inventors have found that the electrode characteristics are remarkably improved when the crystallite diameter of the oxide is 400 to 500 mm and the specific surface area obtained by the BET method by N ₂ adsorption is 40 to 50 m ² / g. .

  As for the synthesis method of the catalyst material, any conventionally known synthesis method such as a dry method or a wet method can be used, and there is no particular limitation.

  As the binder, in addition to the PTFE powder, a PTFE dispersion or a polyvinylidene fluoride (PVdF) powder or dispersion may be used.

As the negative electrode, a metal lithium or a negative electrode made of a substance capable of occluding and releasing lithium ions (carbon, Si, Sn, Li _2.6 Co _0.4 N) can be used. However, as a negative electrode material, a compound such as carbon which does not contain lithium first needs to be chemically or electrochemically changed into a compound such as C ₆ Li containing lithium in advance before producing a battery.

  The non-aqueous electrolyte may be any non-aqueous electrolyte capable of moving lithium ions, and an organic electrolyte or ionic liquid can be used.

As the organic electrolyte, a metal salt such as LiClO ₄ or LiPF ₆ dissolved in an organic solvent such as propylene carbonate (PC), ethylene carbonate (EC) or dimethyl carbonate (DMC), or a mixed solvent thereof is used. can do.

  Various conventionally known materials can be used for battery constituent materials such as separators and battery cases, and there is no particular limitation.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

[Example 1]
Calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98) so that the molar ratio of Ca ions to Mn ions (NCa: NMn) is 1: 1 in 200 cc of ion exchange water. 0.05% (11.99 g) and manganese nitrate hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) powder (purity: 98.0%) 0.05 mol (14.64 g) By heat-treating a powder obtained after evaporating and drying at 250 ° C. for 5 hours, a mixture of the dissolved aqueous solution and an aqueous solution in which 20.32 g of malic acid is dissolved in 200 cc of ion-exchange water at 800 ° C. Brown millelite type oxide Ca ₂ Mn ₂ O ₅ was produced.

FIG. 1 shows an XRD pattern of the produced brown millerite oxide.
In FIG. 1, the positive electrode composed of carbon, an oxide catalyst, and a binder is prepared by mixing an oxide catalyst, carbon powder, and polytetrafluoroethylene (PTFE) powder in a weight ratio of 5: 3: 2, roll forming, A sheet-like electrode having a thickness of 0.5 mm was prepared and cut into a circle having a diameter of 23 mm.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table of FIG. 5, in Example 1, the crystallite diameter was 599 mm, and the specific surface area was 11 m ² / g.

  The negative electrode was produced by cutting out a metal lithium foil having a thickness of 600 μm into a circle having a diameter of 15 mm.

In FIG. 2, the schematic of the cylindrical cell structure of the lithium air secondary battery which concerns on this invention is shown.
In FIG. 2, a cylindrical cell structure 200 of a lithium-air secondary battery includes a positive electrode connector (made of Teflon) 201, an electrode case 202, a positive electrode 203, a separator 204, a metal lithium negative electrode 205, and a negative electrode connector. (Manufactured by SUS) 206, a negative electrode support (manufactured by SUS) 207, an O-ring 208, and a negative electrode terminal 209. The diameter of the circular air hole for taking air into the positive electrode 203 is 16 mm.

  A positive electrode 203 made of carbon, a catalyst, and a binder is placed on one side of an electrode case 202 whose surface is coated with Teflon (no contact with the positive electrode), and the positive electrode 203 is fixed by fitting a Teflon fastener 201. did. Next, an electrolyte solution is injected into the opposite side of the positive electrode of the electrode case 202, a separator 204 is inserted, and a metal lithium negative electrode 205 cut out in a circular shape is pressure-bonded to a negative electrode connector 206 together with a negative electrode support 207. The separator 204 is inserted so as to be sandwiched between the electrode cases 202. Further, the O-ring 208 is attached to the electrode case 202, and the negative electrode terminal 209 is fitted. As the electrolytic solution, a solution in which lithium hexafluorophosphate (LiPF6) was dissolved in a propylene carbonate (PC) solvent at a concentration of 1 mol / l was used.

This battery was subjected to a charge / discharge test at a current density of 0.1 mA / cm ² (standardized by the area of the positive electrode exposed to the atmosphere) at a discharge end voltage of 2.0 V and a charge end voltage of 4.5 V. The capacity was described as the capacity per unit weight of carbon (mAh / g) contained in the positive electrode for the subsequent comparison.

FIG. 3 shows an initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 3, for Example 1, a discharge capacity of 2052 mAh / g and a discharge average voltage of 2.56 V were shown.

[Example 2]
Calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98) so that the molar ratio of Ca ions to Fe ions (NCa: NFe) is 1: 1 in 200 cc of ion exchange water .5%) 0.05 mol (11.99 g) and iron nitrate nonahydrate (Fe (NO ₃ ) ₃ .9H ₂ O) powder (purity: 99.9%) 0.05 mol (20.22 g) By heat-treating a powder obtained after evaporating and drying at 250 ° C. for 5 hours, a mixture of the dissolved aqueous solution and an aqueous solution in which 20.32 g of malic acid is dissolved in 200 cc of ion-exchange water at 800 ° C. Brown millelite type oxide Ca ₂ Fe ₂ O ₅ was produced. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated from the XRD pattern by the Scherrer method. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table of FIG. 5, in Example 2, the crystallite diameter was 542 mm and the specific surface area was 16 m ² / g.

FIG. 3 shows an initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 3, for Example 2, the discharge capacity was 1982 mAh / g and the discharge average voltage was 2.54V.

[Example 3]
0.05 mol of strontium nitrate (Sr (NO ₃ ) ₂ ) powder (purity: 98.0%) so that the molar ratio of Sr ions to Mn ions (NCa: NMn) is 1: 1 in 200 cc of ion exchange water (10.80 g) and a mixed aqueous solution in which 0.05 mol (14.64 g) of manganese nitrate hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O) powder (purity: 98.0%) is dissolved, and 200 cc The powder obtained after evaporating to dryness at 250 ° C. a mixture of an aqueous solution in which 20.32 g of malic acid was dissolved in the ion-exchanged water was heat-treated at 800 ° C. for 5 hours, whereby brown millelite type oxide Sr ₂ Mn ₂ O ₅ was produced. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated from the XRD pattern by the Scherrer method. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table shown in FIG. 5, in Example 3, the crystallite diameter was 794 mm, and the specific surface area was 8.6 m ² / g.

FIG. 3 shows an initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 3, for Example 3, the discharge capacity was 1819 mAh / g and the discharge average voltage was 2.53V.

[Example 4]
0.05 mol of strontium nitrate (Sr (NO ₃ ) ₂ ) powder (purity: 98.0%) in 200 cc ion-exchanged water so that the molar ratio of Sr ions to Fe ions (NCa: NFe) is 1: 1. (10.80 g) and a mixed aqueous solution in which 0.05 mol (20.22 g) of iron nitrate nonahydrate (Fe (NO ₃ ) ₃ .9H ₂ O) powder (purity: 99.9%) is dissolved, and 200 cc The powder obtained after evaporating to dryness at 250 ° C. a mixture of an aqueous solution in which 20.32 g of malic acid was dissolved in the ion-exchanged water was heat-treated at 800 ° C. for 5 hours, whereby brown millelite type oxide Sr ₂ Fe ₂ O ₅ was prepared. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table shown in FIG. 5, in Example 4, the crystallite diameter was 612 mm, and the specific surface area was 11 m ² / g.

FIG. 3 shows an initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 3, for Example 4, the discharge capacity was 1833 mAh / g and the discharge average voltage was 2.46V.

In Example 1, cycle characteristics better than those in Examples 2 to 4 are obtained. This is considered to be because the reversibility of the charge / discharge reaction was further improved and the charge / discharge efficiency was improved by adding the brown millerite type oxide Ca ₂ Mn ₂ O ₅ to the positive electrode.

[Example 5]
In 200 cc of ion exchange water, 0.05 mol (11.99 g) of calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98.5%), manganese nitrate hexahydrate ( 0.045 mol (13.18 g) of Mn (NO ₃ ) ₂ .6H ₂ O) powder (purity: 98.0%), cobalt nitrate tetrahydrate (Co (NO ₃ ) ₂ .4H ₂ O) powder ( Purity: 98.0%) was dissolved in 0.005 mol (1.48 g) of a mixed aqueous solution (manganese and cobalt molar ratio 9: 1), and 20.32 g of malic acid was dissolved in 200 cc of ion-exchanged water. A brown millelite type oxide catalyst in which 10 mol% of manganese oxide is replaced with cobalt by heat-treating the powder obtained after evaporating and drying the mixture of aqueous solutions at 250 ° C. for 5 hours at 800 ° C. Production It was. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table shown in FIG. 5, in Example 5, the crystallite diameter was 769 mm, and the specific surface area was 9.2 m ² / g.

FIG. 3 shows an initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 3, for Example 5, a discharge capacity of 2219 mAh / g and a discharge average voltage of 2.70 V were shown.

[Example 6]
In 200 cc of ion exchange water, 0.05 mol (11.99 g) of calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98.5%), manganese nitrate hexahydrate ( 0.045 mol (13.18 g) of Mn (NO ₃ ) ₂ · 6H ₂ O) powder (purity: 98.0%), nickel nitrate hexahydrate (Ni (NO ₃ ) ₂ · 6H ₂ O) powder ( 20:32 g of malic acid was dissolved in 200 cc of ion-exchanged water in a mixed aqueous solution (purity: 99.0%) dissolved in 0.005 mol (1.47 g) (manganese / nickel molar ratio 9: 1). A brown millelite type oxide catalyst in which 10% of manganese oxide is replaced with nickel by heat-treating the powder obtained after evaporating and drying the mixture of aqueous solutions at 250 ° C. for 5 hours at 800 ° C. Produced. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N2 adsorption. As a result, as shown in the table shown in FIG. 5, in Example 6, the crystallite diameter was 806 mm and the specific surface area was 8.5 m ² / g.

FIG. 3 shows an initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 3, for Example 6, the discharge capacity was 2338 mAh / g and the discharge average voltage was 2.71V.

[Example 7]
In 200 cc of ion exchange water, 0.05 mol (11.99 g) of calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98.5%), manganese nitrate hexahydrate ( 0.045 mol (13.18 g) of Mn (NO ₃ ) ₂ · 6H ₂ O) powder (purity: 98.0%), iron nitrate nonahydrate (Fe (NO ₃ ) ₃ · 9H ₂ O) powder ( Purity: 99.9%) was dissolved in 0.005 mol (2.02 g) of a mixed aqueous solution (manganese / iron molar ratio 9: 1), and 20.32 g of malic acid was dissolved in 200 cc of ion-exchanged water. The powder obtained after evaporating and drying the mixture of the aqueous solutions at 250 ° C. is subjected to heat treatment at 800 ° C. for 5 hours, whereby a brown millerite oxide catalyst Ca ₂ Mn _1.8 in which 10% of manganese is replaced with iron is obtained. Fe _0.2 O ₅ was produced. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table of FIG. 5, in Example 7, the crystallite diameter was 579 mm, and the specific surface area was 14 m ₂ / g.

The initial charge / discharge curves of the lithium air battery produced in this example are shown in FIGS.
3 and 4, Example 7 showed a discharge capacity of 2503 mAh / g and a discharge average voltage of 2.72V.

In Example 7, cycle characteristics better than those in Examples 1 to 6 were obtained. This is considered to be because the reversibility of the charge / discharge reaction was further improved and the charge / discharge efficiency was improved by adding the brown millerite oxide Ca ₂ Mn _1.8 Fe _0.2 O ₅ to the positive electrode.

[Example 8]
In 200 cc of ion exchange water, 0.05 mol (11.99 g) of calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98.5%), manganese nitrate hexahydrate ( 0.045 mol (13.18 g) of Mn (NO ₃ ) 2.6H ₂ O) powder (purity: 98.0%), iron nitrate nonahydrate (Fe (NO ₃ ) ₃ · 9 H ₂ O) powder ( Purity: 99.9%) was dissolved in 0.005 mol (2.02 g) of a mixed aqueous solution (manganese / iron molar ratio 9: 1), and 20.32 g of malic acid was dissolved in 200 cc of ion-exchanged water. A brown millerite type oxide catalyst in which 10% of manganese oxide is replaced with iron by heat-treating the powder obtained after evaporating and drying the mixture of aqueous solutions at 250 ° C. at 650 ° C. for 5 hours. Produced. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table of FIG. 5, in Example 8, the crystallite diameter was 486 mm, and the specific surface area was 25 m ² / g.

FIG. 4 shows the initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 4, for Example 8, the discharge capacity was 2765 mAh / g, and the discharge average voltage was 2.71V.

[Example 9]
In 200 cc of ion exchange water, 0.05 mol (11.99 g) of calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ .4H ₂ O) powder (purity: 98.5%), manganese nitrate hexahydrate ( 0.045 mol (13.18 g) of Mn (NO ₃ ) ₂ · 6H ₂ O) powder (purity: 98.0%), iron nitrate nonahydrate (Fe (NO ₃ ) ₃ · 9H ₂ O) powder ( Purity: 99.9%) was dissolved in 0.005 mol (2.02 g) of a mixed aqueous solution (manganese / iron molar ratio 9: 1), and 20.32 g of malic acid was dissolved in 200 cc of ion-exchanged water. A brown millelite-type oxide catalyst in which 10% of manganese oxide is replaced with iron by heat-treating the powder obtained after evaporating and drying a mixture of aqueous solutions at 250 ° C. for 5 hours at 500 ° C. Produced. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite diameter of the produced oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table of FIG. 5, in Example 9, the crystallite diameter was 433 mm, and the specific surface area was 42 m ² / g.

FIG. 4 shows the initial charge / discharge curve of the lithium-air battery produced in this example.
In FIG. 4, for Example 9, the discharge capacity was 3082 mAh / g and the discharge average voltage was 2.72V.

  In Examples 7 to 9, all of the batteries exhibited a large discharge capacity and good cycle characteristics were obtained. However, a catalyst material having a smaller crystallite diameter and a larger specific surface area has a larger discharge capacity and a smaller charge / discharge overvoltage. It has become. This is because the catalyst dispersion state in the positive electrode has improved, so that not only carbon but also the catalyst becomes a reaction site, and a catalyst material with a smaller crystallite diameter and a larger specific surface area has produced more reaction sites. It is done. In addition, it is considered that the precipitation / decomposition of the discharge product is facilitated by the catalyst, the overvoltage is reduced, and good cycle characteristics are exhibited.

  This is considered to have exhibited good characteristics because the conditions for producing a high-performance positive electrode for a lithium-air battery in the present invention were satisfied.

[Comparative Example 1]
A lithium air battery in which the brown millerite type oxide produced in Example 1 and a commercially available manganese oxide (M _n O ₂ powder) were mixed as a catalyst with the positive electrode was compared. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite size of the oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table shown in FIG. 5, in Comparative Example 1, the crystallite diameter was 925 mm and the specific surface area was 0.8 m ² / g.

  The discharge curve of the lithium air battery produced in this comparative example is shown in FIG. Along with the discharge capacity of the battery, the crystallite diameter and specific surface area of the manganese oxide are shown in the table shown in FIG.

  The above comparative example has worse cycle characteristics than any of Examples 1-9. This is considered to be because the brown millelite type oxide catalyst is more likely to promote the precipitation and decomposition of the discharge product during charge and discharge. In addition, it is considered that the catalyst material having a small crystallite and a large specific surface area increases the reaction site on the positive electrode and further promotes the reactivity of precipitation and decomposition reaction of the reaction product accompanying charge / discharge. .

[Comparative Example 2]
A lithium air battery in which the brown millerite type oxide produced in Example 9 and a high surface area manganese oxide (Mn ₂ O ₃ powder) were mixed with the positive electrode as a catalyst was compared. Other battery fabrication and measurement methods were performed in the same manner as in Example 1.

The crystallite size of the oxide was calculated by the Scherrer method from the XRD measurement results. The specific surface area was calculated by the BET method using N ₂ adsorption. As a result, as shown in the table of FIG. 5, in Comparative Example 2, the crystallite diameter was 129 kg, and the specific surface area was 80 m ² / g.

  The discharge curve of the lithium air battery produced in this comparative example is shown in FIG. Table 1 shows the crystallite diameter and specific surface area of the manganese oxide together with the discharge capacity of the battery.

  Although the above comparative example had a large initial discharge capacity, the cycle characteristics were worse than those of Examples 1-9. This is probably because the surface area was too large (because the crystallites were too small) and the stability of the catalyst deteriorated.

  As described above, according to the present invention, a high-performance lithium-air secondary battery can be manufactured and used as a drive source for various electronic devices.

DESCRIPTION OF SYMBOLS 201 Positive electrode joint 202 Electrode case 203 Carbon positive electrode 204 Separator 205 Metal lithium negative electrode 206 Negative electrode joint 207 Negative electrode support 208 O-ring 209 Negative electrode terminal

Claims (5)

A positive electrode made of carbon, a catalyst, and a binder;
A negative electrode made of a material capable of occluding and releasing metallic lithium or lithium ions,
The positive electrode of one side air, as the other side is in contact with the non-aqueous electrolyte, the lithium air battery constructed by placing a non-aqueous electrolytic solution between the positive electrode and the negative electrode,
The catalyst of the positive electrode is a brown millerite type oxide (A ₂ B ₂ O ₅ ) , and the A ₂ B ₂ O ₅ is at least 1 each of A = Ca, Sr, B = Mn, Fe, Co, and Ni. Lithium-air secondary battery characterized by using two. The brownmillerite type oxide, A = Ca, Sr, B = Mn, according to claim 1, characterized in that the brownmillerite type oxide that is prepared by using at least one of each of Fe Lithium air secondary battery. The brownmillerite type oxide, A = Ca, using B = Mn, a portion of the Mn Fe, Co, brownmillerite type oxide was replaced by _{Ni (Ca 2 Mn 2-x} M x O _5, M = Fe, Co, lithium-air secondary cell according to claim 1, characterized in that a Ni). The brown millerite type oxide has a crystallite diameter of 400 to 500 mm, and
Lithium-air secondary cell according to any one of claims 1 to 3, wherein the specific surface area determined by BET method using N ₂ adsorption is 40 to 50 m ² / g. Mixing carbon, a catalyst, and a binder to produce a positive electrode;
Producing a negative electrode using a material capable of occluding and releasing metallic lithium or lithium ions;
The positive electrode of one side air, as the other side is in contact with the non-aqueous electrolyte, comprising the steps of placing a non-aqueous electrolytic solution between the positive electrode and the negative electrode,
The catalyst of the positive electrode is a brown millelite type oxide (A ₂ B ₂ O ₅ ) , and the A ₂ B ₂ O ₅ is at least 1 each of A = Ca, Sr, B = Mn, Fe, Co, and Ni. A method for producing a lithium-air secondary battery, characterized by using two .

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