JP6315708B2 - Lithium-air secondary battery, method for producing lithium-air secondary battery, and apparatus equipped with lithium-air secondary battery - Google Patents

Description

  The present invention relates to a lithium air secondary battery, a method for producing a lithium air secondary battery, and an apparatus including the lithium air secondary battery.

  The metal-air battery has a theoretical energy density far exceeding that of a lithium ion battery using a non-aqueous electrolyte. For this reason, research on metal-air batteries is underway on a worldwide scale. Examples of metal-air batteries currently being studied include primary batteries such as lithium-air primary batteries, zinc-air primary batteries, zinc-chlorine primary batteries, zinc-bromine primary batteries, lithium-air secondary batteries, zinc-air secondary batteries, There are secondary batteries such as a zinc-chlorine secondary battery and a zinc-bromine secondary battery.

  As a metal-air battery in practical use, for example, there is a zinc-air primary battery. Zinc-air primary batteries have a large discharge capacity of about 300 mAh / g, and are therefore mainly used for hearing aids. However, since the voltage of the zinc-air primary battery is only about 1V, there is a problem that it is difficult to use it widely like a lithium ion battery.

  In recent years, as with the zinc-air battery, electrochemical reduction (discharge) and generation (charge) of oxygen are used as the positive electrode reaction system, lithium metal is used as the negative electrode, and a nonaqueous electrolyte is used as the electrolyte. Attempts have been made to produce a lithium-air secondary battery that exhibits a high voltage of 2 to 3 V.

  According to the trial, the lithium-air secondary battery can obtain a large discharge capacity of 1000 mAh / g or more in the first discharge. However, because the voltage during charging (charging voltage) is high, decomposition of the non-aqueous electrolyte occurs and the reversibility of discharge product (lithium oxide) deposition and decomposition is insufficient, When the cycle is repeated, the discharge capacity is significantly reduced.

  In order to solve the above-mentioned problem in the lithium air secondary battery, attempts have been made to increase the activation of the electrode by adding a catalyst to the positive electrode for the lithium air secondary battery. For example, Non-Patent Document 1 reports the results of conducting a charge / discharge test by adding platinum or various metal oxides as a catalyst to the positive electrode of a lithium-air secondary battery.

According to Non-Patent Document 1, when MnO ₂ is added as a catalyst, the initial discharge capacity is 1000 mAh / g, and the capacity after 50 cycles is reported to be 600 mAh / g. Further, according to Non-Patent Document 1, it is reported that when Fe ₂ O ₃ is added as a catalyst, the initial discharge capacity is 2700 mAh / g, and the capacity after 10 cycles is 75 mAh / g. According to Non-Patent Document 1, it is reported that when Fe ₃ O ₄ is added as a catalyst, the initial discharge capacity is about 1200 mAh / g and the capacity after 10 cycles is 800 mAh / g. .

A. Debart, J .; Bao, G.M. Armstrong, P.M. G. Bruce, “An O 2 cathode for rechargeable lithium batteries: The effect of a catalyst”, Journal of Power Sources, Vol. 174, P.I. 1177-1182 (2007)

  However, the conventional lithium-air secondary battery has a problem that the charging voltage is high as described above. In addition, the lithium-air secondary battery described in Non-Patent Document 1 has a significant capacity reduction due to the charge / discharge cycle, so that it is necessary to further improve cycle characteristics for practical use as a secondary battery. was there.

  The present invention has been made in view of the above problems, and provides a lithium-air secondary battery having a low charging voltage and excellent cycle characteristics, a method for producing a lithium-air secondary battery, and an apparatus including the lithium-air secondary battery. The task is to do.

  The lithium-air secondary battery according to the present invention comprises a catalyst, one surface is in contact with air, the other surface is in contact with a nonaqueous electrolyte, and at least one of metallic lithium and lithium ions. A lithium-air secondary battery comprising a non-aqueous electrolyte disposed between the positive electrode and the negative electrode. And a cyanide compound.

  Thus, this invention contains the cyanide compound as a catalyst contained in a positive electrode. Since the cyanide compound has high activity, it is possible to obtain good reversibility of precipitates (discharge products) generated during discharge, that is, to promote decomposition of the discharge products. Therefore, according to the present invention, the charging voltage can be lowered and the decomposition of the electrolytic solution can be suppressed, so that the cycle characteristics can be improved.

  In the lithium air secondary battery according to the present invention, the cyan compound is preferably at least one of copper cyanide, sodium cyanide, potassium cyanide, and silver cyanide.

  Thus, since this invention contains the specific cyanide compound as a catalyst used for a positive electrode, while being able to lower a charging voltage more, it can be made more excellent in cycling characteristics.

  The lithium-air secondary battery according to the present invention is preferably a powder body obtained by heat-treating the cyanide compound at 100 to 400 ° C.

  In this way, moisture in the cyanide is dehydrated by the heat treatment, preventing deterioration of battery performance due to moisture mixing, and the weight is reduced, so more cyanide is included even at the same compounding amount. Can do. Accordingly, the charging voltage can be further reduced and the cycle characteristics can be further improved.

  A method for producing a lithium-air secondary battery according to the present invention comprises a positive electrode comprising a catalyst, having one surface in contact with air and the other surface in contact with a non-aqueous electrolyte, and metal lithium and lithium ions. A negative electrode comprising a substance capable of inserting and extracting at least one of the above, a non-aqueous electrolyte disposed between the positive electrode and the negative electrode, and a lithium containing a cyanide compound as the catalyst A manufacturing method for manufacturing an air secondary battery, comprising: a dispersion preparing step of preparing a dispersion by dispersing the cyanide compound in a volatile solvent; and evaporating and drying the dispersion to a predetermined shape. And a first positive electrode manufacturing step of manufacturing a positive electrode by molding.

  If it does in this way, the lithium air secondary battery concerning this invention which comprises the positive electrode containing the cyanide compound as a catalyst can be manufactured.

  A method for producing a lithium-air secondary battery according to the present invention comprises a positive electrode comprising a catalyst, having one surface in contact with air and the other surface in contact with a non-aqueous electrolyte, and metal lithium and lithium ions. A negative electrode comprising a substance capable of inserting and extracting at least one of the above, a non-aqueous electrolyte disposed between the positive electrode and the negative electrode, and a lithium containing a cyanide compound as the catalyst A manufacturing method for manufacturing an air secondary battery, comprising: a dispersion preparation step in which the cyanide compound is dispersed in a volatile solvent to prepare a dispersion; and the dispersion is applied onto a positive electrode current collector and dried. And the second positive electrode manufacturing step of manufacturing the positive electrode by repeating 2 to 5 times.

  Even in this case, the lithium-air secondary battery according to the present invention including the positive electrode containing the cyanide compound as the catalyst can be produced. In addition, since the lithium air secondary battery manufactured by this manufacturing method is manufactured by laminating the positive electrode, a new three-phase interface is formed between the layers. Therefore, the charging voltage can be further reduced and the cycle characteristics can be further improved.

  In the method for producing a lithium-air secondary battery according to the present invention, it is preferable that the cyanide compound is at least one of copper cyanide, sodium cyanide, potassium cyanide, and silver cyanide.

  If it does in this way, the lithium air secondary battery containing the specific cyanide compound as a catalyst used for a positive electrode can be manufactured. For this reason, the manufactured lithium-air secondary battery can further reduce the charging voltage and have more excellent cycle characteristics.

  In the method for producing a lithium-air secondary battery according to the present invention, the cyan compound is preferably a powder obtained by heat treatment at 100 to 400 ° C.

  If it does in this way, the lithium air secondary battery containing the cyanide heat-processed at 100-400 degreeC as a catalyst used for a positive electrode can be manufactured. For this reason, the manufactured lithium-air secondary battery can further reduce the charging voltage and have more excellent cycle characteristics.

  The apparatus according to the present invention includes the lithium-air secondary battery according to the present invention.

  Since the apparatus according to the present invention includes the lithium-air secondary battery according to the present invention, the charging voltage is low and the cycle characteristics can be excellent.

  ADVANTAGE OF THE INVENTION According to this invention, the charging voltage is low and can provide the apparatus provided with the manufacturing method of the lithium air secondary battery which was excellent in cycling characteristics, the lithium air secondary battery, and the lithium air secondary battery.

It is a schematic sectional drawing explaining the example of 1 structure of the lithium air secondary battery which concerns on this embodiment. It is a flowchart explaining the manufacturing method of the lithium air secondary battery which concerns on this embodiment. No. It is a graph which shows the first time charge / discharge curve of the lithium air secondary battery which concerns on 1-5. The horizontal axis indicates capacity (Capacity; mAh / g), and the vertical axis indicates voltage (Voltage; V). In the figure, “a” indicates No. using NaCN as the catalyst of the positive electrode. 1 represents a charge / discharge curve of the lithium air secondary battery according to FIG. 2 represents a charge / discharge curve of the lithium-air secondary battery according to FIG. 3 represents a charge / discharge curve of the lithium air secondary battery according to No. 3, wherein “d” is a No. 3 using AgCN. 4 represents a charge / discharge curve of the lithium-air secondary battery according to No. 4, wherein “e” is a No. 1 catalyst using no catalyst. 5 shows a charge / discharge curve of the lithium-air secondary battery according to FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a lithium-air secondary battery, a method for producing a lithium-air secondary battery, and an apparatus including a lithium-air secondary battery according to the present invention will be described in detail with reference to the drawings as appropriate.

[Lithium air secondary battery]
(Basic configuration of lithium-air secondary battery)
First, with reference to FIG. 1, the lithium air secondary battery 10 which concerns on this embodiment is demonstrated.
A lithium air secondary battery 10 shown in FIG. 1 includes, for example, a positive electrode connector 1, an electrode case 2, a positive electrode 3, a separator 4, a negative electrode 5, a negative electrode connector 6, a negative electrode support 7, an O-ring 8, and a negative electrode terminal 9. It is configured to include. In addition, although the lithium air secondary battery 10 which concerns on this embodiment shown in FIG. 1 has shown the example comprised as a cylindrical cell, it is not limited to this, A square type, a button type, a coin type, a flat type, etc. The desired shape can be obtained.

  The positive electrode connector 1, the negative electrode connector 6, the negative electrode support 7, and the negative electrode terminal 9 have conductivity such as Fe, Ni, Ti, Au, or an alloy mainly composed of any one selected from these. It is preferable to make it with the material which has. When it is desired to reduce the manufacturing cost, the positive electrode connector 1, the negative electrode connector 6, the negative electrode support 7, and the negative electrode terminal 9 are preferably manufactured using, for example, Fe or an Fe alloy. SUS (Special Use Stainless steel) It is more preferable to produce using stainless steel for use). Moreover, when it is desired to obtain high conductivity, the positive electrode connector 1, the negative electrode connector 6, the negative electrode support 7, and the negative electrode terminal 9 are preferably manufactured using, for example, Au or an Au alloy.

  As shown in FIG. 1, the positive electrode connector 1, the electrode case 2, and the negative electrode connector 6 are preferably a cylindrical body or an annular body. The inner diameters of the positive electrode connector 1 and the negative electrode connector 6 forming a cylindrical body or an annular body can be set as appropriate, and can be set to 16 mm, for example. In addition, in order to fix the positive electrode 3 and the separator 4 inside the electrode case 2, it has the stopper 2a extended in the direction where an internal diameter becomes small. Specifically, the positive electrode 3 is fixed by the positive electrode connector 1 and the stopper 2a, and the separator 4 is fixed by the negative electrode support 7 and the stopper 2a.

The positive electrode connector 1 enables contact between the positive electrode 3 and air by the inner hole 1a.
Inside the negative electrode support 7, the negative electrode 5 is disposed so as to contact the separator 4, and further, one end surface of the negative electrode connector 6 is disposed so as to contact the negative electrode 5. The other end surface of the negative electrode connector 6 is in contact with the negative electrode terminal 9 together with the negative electrode support 7.
The positive electrode 3 and the negative electrode 5 will be described later.

  The electrode case 2 can be formed of a metal such as SUS or a fluororesin. When the electrode case 2 is formed of metal, it is preferable that the entire surface is coated with a fluororesin or the like except for a portion that contacts the positive electrode 3 such as the stopper 2a. By coating the surface of the electrode case 2 with a fluororesin or the like and performing an insulation treatment, it is possible to prevent a short circuit during battery production.

  The separator 4 is preferably provided so that the positive electrode 3 and the negative electrode 5 do not come into contact with each other and can be impregnated with the non-aqueous electrolyte NE. Specifically, the separator 4 is preferably a porous film having a microporous structure. The separator 4 is a single material selected from, for example, polyethylene, polypropylene, poly-4-methyl-1-pentene, polyphenylene ether, polyamide, polyimide, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, and the like. It is more preferable to use a porous film using the above resin or a mixture of two or more.

  The non-aqueous electrolyte NE may be any non-aqueous electrolyte that can move lithium ions, and an organic electrolyte or ionic liquid can be used.

Examples of the organic electrolyte include LiClO ₄ , LiPF ₆ , LiBF ₄ , lithium bis (trifluoromethanesulfonyl) amide (LiN (CF ₃ SO ₂ ) ₂ ), LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ( CF ₃ SO ₂ ) ₃ and other metal salts such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1 , 2-diethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and other organic solvents, or Can be dissolved in the mixed solvent. Also, vinylene carbonate (VC) can be added to the organic electrolyte.

  Examples of the ionic liquid include at least one of an imidazolium cation, a pyridinium cation, an aliphatic cation, a phosphonate cation, and an iodine cation, and a halogen anion. A combination of at least one of an ion, a boron-based anion, and a phosphorus-based anion can be used.

Specifically, as the non-aqueous electrolyte NE, a solution obtained by dissolving LiPF ₆ in propylene carbonate (PC) at a concentration of 1 mol / L can be preferably used.

The nonaqueous electrolytic solution NE may be present in the form of a polymer electrolyte or a gel electrolyte.
For example, polyethylene oxide may be used as the polymer electrolyte.
For the gel electrolyte, for example, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyurethane, polyacrylate, cellulose, or the like may be used.

  The electrode case 2 can be made of a material that is usually used as an exterior material of a metal-air battery, such as a metal can, a resin, or a laminate pack.

  In the electrode case 2 and the negative electrode terminal 9, grooves 2b and 9a having a circular cross section and a circular shape when viewed from the front are formed at positions corresponding to each other. The electrode case 2 and the negative electrode terminal 9 are formed by sandwiching an O-ring 8 between the groove portions 2b and 9a. The O-ring 8 is preferably made of, for example, nitrile rubber, fluorine rubber, ethylene propylene rubber, silicone rubber, acrylic rubber, hydrogenated nitrile rubber, or the like. When the O-ring 8 is formed of these materials, the non-aqueous electrolyte NE is unlikely to be altered or corroded, and the leakage of the non-aqueous electrolyte NE is prevented and the function as a lithium-air secondary battery is maintained for a long time. Can be.

  Further, the lithium air secondary battery 10 is configured by disposing at least the non-aqueous electrolyte NE between the positive electrode 3 and the negative electrode 5. More specifically and preferably, the non-aqueous electrolyte NE is a section formed by the positive electrode 3, the separator 4 and the stopper 2 a, and a section formed by the stopper 2 a, the electrode case 2, the separator 4 and the negative electrode support 7. A section formed by the negative electrode connector 6, the negative electrode support 7 and the negative electrode terminal 9, and a section formed by the electrode case 2, the negative electrode terminal 9, the negative electrode support 7 and the O-ring 8 are also filled. These sections are connected to each other through a through hole not shown in FIG. Therefore, the nonaqueous electrolytic solution NE can freely flow through these sections through the through holes.

(Positive electrode and negative electrode)
As shown in FIG. 1, the positive electrode 3 is in contact with air on one surface fixed by the positive electrode connector 1, and is in contact with the non-aqueous electrolyte NE on the other surface. In the present invention, the positive electrode 3 contains a cyanide compound as a catalyst. The positive electrode 3 contains carbon that functions as a conductive material. The positive electrode 3 has a plurality of holes (nanoscale holes) formed by using carbon and having a size that prevents the nonaqueous electrolyte solution NE from leaking. The positive electrode 3 can use oxygen in the air as a positive electrode active material through the hole. Therefore, in the positive electrode 3, an electrochemical redox reaction of oxygen, which is a positive electrode active material, proceeds. In addition, the discharge reaction on the positive electrode 3 can be expressed as the following formula (1) or (2).

2Li ⁺ + O ₂ + 2e ⁻ → Li ₂ O ₂ (1)

2Li ⁺ +1/2 (O ₂ ) + 2e ⁻ → Li ₂ O (2)

Lithium ions (Li ⁺ ) in the above formulas (1) and (2) have moved from the negative electrode 5 to the surface of the positive electrode 3 through the nonaqueous electrolytic solution NE. Oxygen (O ₂ ) is taken into the positive electrode 3 from the atmosphere. When the Li ₂ O ₂ or Li ₂ O produced by this discharge reaction is deposited on the positive electrode 3 and all the reaction sites on the positive electrode 3 are covered, the discharge reaction is completed. At the time of charging, a reaction opposite to the discharge reaction occurs, and charging is terminated when all of the discharge products generated at the time of decomposition are decomposed.

  The cyan compound contained in the positive electrode 3 is preferably at least one of, for example, copper cyanide (CuCN), sodium cyanide (NaCN), potassium cyanide (KCN), and silver cyanide (AgCN). That is, any one of these can be used, and two or more can be used together. As the catalyst in the present invention, it is preferable to use copper cyanide from the viewpoint of lowering the charging voltage and improving the cycle characteristics.

The cyan compound is preferably heat-treated. The heat treatment is preferably performed at 100 to 400 ° C., for example. In this way, the moisture in the catalyst is dehydrated by the heat treatment, the battery performance can be prevented from deteriorating due to the mixing of moisture, and the mass can be reduced, so that more cyan compounds can be included. . Therefore, it can be made more excellent in cycle characteristics. The heat treatment temperature is more preferably 200 ° C. In this case, since the heat treatment is performed at a relatively low temperature, the crystallinity is hardly affected, the dispersibility of the catalyst in the positive electrode 3 is maintained, and the effect of the catalyst can be exhibited over a wide range. Therefore, the cycle characteristics can be further improved.
The heat treatment conditions are not limited to those described above. The heat treatment only needs to be able to dehydrate moisture in the cyanide compound, and can be performed at a temperature lower than 100 ° C. or higher than 400 ° C. The heat treatment time can be, for example, about 1 to 12 hours, but it is sufficient that the moisture in the cyanide compound can be dehydrated. The heat treatment time may be less than 1 hour, or more than 12 hours. It can also be. The heat treatment is preferably performed in an inert gas atmosphere such as argon or helium. The catalyst contained in the positive electrode 3 has, for example, at least one characteristic of a crystallite diameter of 400 to 500 mm and a specific surface area determined by a BET method by N ₂ adsorption of 40 to 50 m ² / g or more. Is preferred. When such a catalyst is used, a lithium air secondary battery excellent in cycle characteristics can be provided more reliably.

Examples of carbon contained in the positive electrode 3 include carbon black, ketjen black, acetylene black, activated carbon, carbon fiber, channel black, furnace black, and mesoporous carbon. It is desirable to use high surface area carbon having a small particle size and many reaction sites. The carbon contained in the positive electrode 3 has, for example, a crystallite diameter calculated from the Scherrer equation in X-ray diffraction measurement of 15 mm or less, and a specific surface area determined by the BET method by N ₂ adsorption is 750 m ² / The total pore volume determined by the mercury intrusion method is 4.0 ml / g or more and 5.5 ml / g or less, and the ratio of the primary pore volume to the total pore volume is 30% or more and 45% or less. It is preferable that the contact angle has at least one feature of 95 ° to 115 °. When such carbon is used, a lithium-air secondary battery excellent in cycle characteristics can be provided more reliably.

The positive electrode 3 can contain the binder and volatile solvent used in the manufacturing process in addition to the above-described carbon and catalyst.
As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine resins such as fluorine rubber, polypropylene, polyethylene, polyacrylonitrile, styrene butadiene rubber (SBR), and the like can be used.
Examples of the volatile solvent include organic solvents such as N-methyl-2-pyrrolidone (NMP) and acetone. However, the volatile solvent is not limited to these as long as it is used for the production of a positive electrode of an air metal battery. It can be used without being done.

  In the positive electrode 3 in the present invention, the mixing ratio of the catalyst, carbon, and binder described above is catalyst: carbon: binder, and may be, for example, 5: 3: 2 (mass ratio), but is not limited thereto. Any ratio can be used as long as the desired effect of the present invention is achieved.

The positive electrode 3 is preferably provided with a positive electrode current collector (not shown in FIG. 1) adjacent to the positive electrode 3. The positive electrode current collector is preferably disposed on the surface in contact with air, but can also be disposed between the positive electrode 3 and the non-aqueous electrolyte NE. The positive electrode 3 can also be formed so as to cover the surface of the positive electrode current collector.
The positive electrode current collector is not particularly limited as long as it is a porous structure such as carbon paper or a metal mesh, a network structure, a fiber, or a nonwoven fabric. Among these, as the positive electrode current collector, for example, a metal mesh formed from SUS, nickel, aluminum, iron, titanium, or the like is preferably used. A metal foil having an oxygen supply hole can also be used as the positive electrode current collector.

The negative electrode 5 includes a substance that can occlude and release at least one of metallic lithium and lithium ions. Examples of such a substance include carbon, Si, Sn, Li _2.6 Co _0.4 N, and the like. Of these, carbon that does not contain lithium ions as a negative electrode material is first chemically or electrochemically chemically changed to a lithium-containing compound (for example, C ₆ Li) before manufacturing the battery. It is preferable to leave.

Arbitrary additives etc. can be added to the positive electrode 3 and the negative electrode 5 as needed.
For example, a catalyst other than the above-described catalyst, a noble metal, an organic material, or the like can be added to the positive electrode 3. Examples of the catalyst other than the above-described catalyst include cobalt oxide and cerium oxide. Examples of the noble metal include Pt, Pd, Au, and Ag. Examples of the organic material include metal phthalocyanines such as cobalt phthalocyanine, Fe porphyrin, and the like.
Moreover, negative electrode active materials, such as an alloy containing a lithium atom, an oxide, nitride, or sulfide, can be added to the negative electrode 5, for example. Examples of the alloy having a lithium atom include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy. Examples of the metal oxide having a lithium atom include lithium titanium oxide. Examples of the metal nitride containing a lithium atom include lithium cobalt nitride, lithium iron nitride, and lithium manganese nitride.

  In the lithium air secondary battery 10 according to the present embodiment described above, since the positive electrode 3 contains a cyanide compound as a catalyst, it is possible to promote decomposition of precipitates generated during discharge. Therefore, the lithium air secondary battery 10 can reduce the charging voltage, and can suppress the decomposition of the non-aqueous electrolyte NE. As a result, the lithium air secondary battery 10 can obtain very excellent cycle characteristics.

With reference to FIG. 1, the manufacturing method (assembly method) of the lithium air secondary battery 10 which concerns on this embodiment is demonstrated.
The lithium air secondary battery 10 according to the present embodiment can be manufactured as follows, for example.
First, the positive electrode 3 is put into one opening of the electrode case 2 and pushed into the stopper 2a to be arranged. Then, the positive electrode 3 is fixed by fitting the positive electrode connector 1 into one opening.
Next, the non-aqueous electrolyte NE is injected into the other opening of the electrode case 2 and the separator 4 is inserted. Further, the negative electrode 5 cut out in a circular shape is pressure-bonded to the negative electrode connector 6.
Then, the pressure-bonded negative electrode 5 and negative electrode connector 6 are inserted into the other opening of the electrode case 2 together with the negative electrode support 7, and the separator 4 is sandwiched and fixed by the stopper 2a.
Next, the O-ring 8 is attached to the electrode case 2 and the negative electrode terminal 9 is fitted and fixed.
By doing in this way, the lithium air secondary battery 10 can be produced.

[Method for producing lithium-air secondary battery]
Next, with reference to FIG. 2, the manufacturing method of the lithium air secondary battery 10 which concerns on this embodiment is demonstrated. In addition, the same code | symbol is attached | subjected about the element same as the lithium air secondary battery 10 demonstrated with reference to FIG. 1, and the overlapping description about the said element is abbreviate | omitted.

FIG. 2 shows a flowchart for manufacturing the positive electrode 3 among the manufacturing methods of the lithium-air secondary battery.
As shown in FIG. 2, the present manufacturing method includes a dispersion preparation step S2 and a positive electrode manufacturing step (a “first positive electrode manufacturing step” or a “second positive electrode manufacturing step” defined in the claims). Equivalent) S3, and these steps are performed in this order. In the present invention, it is preferable that a heat treatment step S1 is included before the dispersion preparation step S2. Steps other than these steps (for example, a step of manufacturing the negative electrode 5, the electrode case 2, the separator 4, etc.) can be performed in the same manner as in the case of manufacturing a general lithium-air secondary battery.
In the present invention, before the heat treatment step S1, before the dispersion preparation step S2, between the heat treatment step S1 and the dispersion preparation step S2, between the dispersion preparation step S2 and the positive electrode production step S3, and at the positive electrode production step. Other optional steps can be performed after S3. Hereinafter, a positive electrode manufacturing method including a heat treatment step S1, a dispersion preparation step S2, and a positive electrode manufacturing step S3, which are preferable embodiments, will be described.

(Heat treatment process)
The heat treatment step S1 is a step of heat treating the cyanide compound used in the dispersion preparation step S2. The heat treatment is performed, for example, at 100 to 400 ° C., more preferably 200 ° C., and preferably for about 1 to 12 hours. Moreover, it is preferable to perform heat processing in inert gas atmosphere, such as argon and helium. Since these conditions have already been described, description thereof is omitted here. By performing the heat treatment, moisture in the cyanide compound is dehydrated, so that it is possible to prevent the battery performance from being deteriorated due to moisture mixing, and since the mass is light, more cyanide compound can be included even in the same blending amount. . Accordingly, the charging voltage can be further reduced and the cycle characteristics can be further improved. The heat treatment step S1 is preferably performed, but is an optional step that may not be performed.

(Dispersion preparation process)
The dispersion preparation step S2 is a step of preparing a dispersion by dispersing a cyanide compound in a volatile solvent. The dispersion is preferably prepared so that the mixing ratio of the catalyst, carbon, and binder is catalyst: carbon: binder, for example, 5: 3: 2 (mass ratio). This dispersion preparation step S2 is an essential step.

(Positive electrode manufacturing process)
In this invention, the following 1st positive electrode manufacturing process or 2nd positive electrode manufacturing process is mentioned as positive electrode manufacturing process S3. In addition, this positive electrode manufacturing process S3 is an essential process.

(First positive electrode manufacturing process)
The first positive electrode manufacturing step is a step of manufacturing the positive electrode 3 by evaporating and drying the dispersion and then forming the dispersion into a predetermined shape.
The dispersion can be evaporated and dried by known means such as natural drying, warm air drying, freeze drying, and vacuum drying. If it does in this way, the volatile solvent in a dispersion liquid is volatilized, and about 0.05-0.5-mm-thick sheet-like solid substance can be obtained.
The positive electrode 3 can be formed into a predetermined shape by, for example, punching the above-described sheet-like solid with a punching machine or cutting with a cutting machine.

(Second positive electrode manufacturing process)
On the other hand, the second positive electrode manufacturing step is a step of manufacturing the positive electrode 3 by repeatedly applying the dispersion liquid on the positive electrode current collector and drying it 2 to 5 times. That is, the second positive electrode manufacturing step is different from the first positive electrode manufacturing step in that the dispersion is applied to the positive electrode current collector. Therefore, the positive electrode 3 manufactured by the second positive electrode manufacturing step has a positive electrode current collector in the positive electrode 3 (not shown in FIG. 1) or on at least one surface of the positive electrode 3. As described above, when the positive electrode current collector is provided, current can be effectively supplied to oxygen as the positive electrode active material, and the output of the battery and the like can be improved.

  The positive electrode current collector can be made of a conductive material such as Fe, Ni, Ti, Au, or an alloy thereof, for example, SUS, similarly to the positive electrode connector 1 or the like.

  For example, a gravure coater, roll coater, comma coater, knife coater, air knife coater, curtain coater, flow coater, kiss coater, shower coater, wheeler coater, spin coater, screen printing, applicator It can be carried out with a coating (printing) machine such as a bar coater. The dispersion liquid can be applied to the positive electrode current collector by dipping, spraying, brushing, or the like.

  As described above, the application and drying of the dispersion liquid to the positive electrode current collector is preferably performed by repeating the coating and drying operations 2 to 5 times. If it does in this way, the three-phase interface which nonaqueous electrolyte NE, air, and the positive electrode 3 contact can be formed moderately in the interlayer of the manufactured positive electrode 3. FIG. Therefore, the positive electrode 3 manufactured in this way can further reduce the charging voltage and can have better cycle characteristics. Note that the dispersion liquid may be applied to the positive electrode current collector and dried once.

  When applying the dispersion liquid to the positive electrode current collector and drying a predetermined number of times to obtain the positive electrode 3, it is preferable to finally perform at least one of a cold press and a hot press. The cold press refers to pressing at a temperature of about room temperature, and the hot press refers to pressing by heating to, for example, 80 to 100 ° C. If it does in this way, the intensity | strength of the positive electrode 3 can be raised and the leakage of the non-aqueous electrolyte NE can be prevented. Since the effect can be obtained more reliably by performing hot pressing, it is preferable to perform hot pressing without fail.

  Since the manufacturing method of the lithium air secondary battery described above performs the steps described above, the lithium air secondary battery 10 including a cyanide compound as a catalyst for the positive electrode 3 can be manufactured. In addition, the lithium air secondary battery 10 can be obtained by assembling (manufacturing) the positive electrode 3 manufactured by this method by the above-described assembly method.

[apparatus]
An apparatus (not shown) according to the present invention includes the above-described lithium-air secondary battery 10 according to the present invention as a power source. Examples of the device include a smartphone, a tablet terminal, a mobile phone, a laptop computer, a hearing aid, and other electronic devices that can use a secondary battery. Since the apparatus according to the present invention includes the lithium-air secondary battery 10 according to the present invention as a power source, the charging voltage is low and the cycle characteristics are excellent.

  Next, the lithium-air secondary battery and the method for producing the lithium-air secondary battery of the present invention will be specifically described with reference to examples.

[Example 1]
As the catalyst used for the positive electrode, NaCN (purity 97%), KCN (purity 98%), CuCN (purity 98%), and AgCN (purity 99%) were prepared (all are commercially available powders).
Each of the above-described various cyanide compounds, ketjen black EC600JD, and polytetrafluoroethylene (PTFE) powder as a catalyst, carbon, and binder are mixed at a mass ratio of 5: 3: 2 and roll-molded. A sheet-like electrode having a thickness of 0.5 mm was obtained. Then, this sheet-like electrode was cut into a circle having a diameter of 23 mm. The positive electrodes according to 1-4 were manufactured.
For comparison, No. made of carbon (Ketjen Black EC600JD) and binder (PTFE) without adding a catalyst. 5 was prepared in the same manner as described above (carbon: binder mass ratio 6: 4, no catalyst).

Using the manufactured positive electrode, a cylindrical lithium-air secondary battery shown in FIG. 1 was manufactured as described below.
On the one side of the electrode case 2 whose surface was coated with Teflon (registered trademark) (the part in contact with the positive electrode 3 was not coated) One of the positive electrodes 3 according to 1 to 5 was arranged, and the positive electrode 3 was fixed by fitting the positive electrode connector 1 whose surface was coated with Teflon.
Next, after injecting the non-aqueous electrolyte NE on the opposite side of the positive electrode 3 of the electrode case 2, the separator 4 is inserted, and the negative electrode 5 made of metallic lithium cut out in a circular shape is pressure-bonded to the negative electrode connector 6. Then, the separator 4 was fitted together with the negative electrode support 7 so as to be sandwiched between the electrode cases 2.
Further, an O-ring 8 was attached to the electrode case 2 and a negative electrode terminal 9 was fitted.
Incidentally, the nonaqueous electrolytic solution, propylene carbonate (PC) solvent, was used after dissolving lithium hexafluorophosphate (LiPF ₆₎ at a concentration of 1 mol / L.

No. No. 1 manufactured using the positive electrode 3 according to 1-5. 1 to 5 with a current density of 0.1 mA / cm ² (normalized by the area of the positive electrode 3 exposed to the atmosphere), a discharge end voltage of 2.0 V and a charge end voltage of 4.5 V. The charge / discharge test was conducted under the conditions.
No. Table 1 shows the discharge capacity in each cycle (first time, 20th time, 50th time) of the lithium air secondary batteries according to 1 to 5 together with the type of cyanide compound used as a catalyst. In addition, the capacity | capacitance shown in Table 1 was described with the capacity | capacitance per mass (mAh / g) of the carbon contained in a positive electrode for subsequent comparison.

  As shown in Table 1, No. 1 containing a cyanide compound as the positive electrode catalyst. The lithium air secondary batteries according to No. 1 to No. 4 are No. 1 containing no cyanide compound as a positive electrode catalyst. As compared with the lithium air secondary battery according to No. 5, the cycle characteristics were excellent. Among these, No. 1 containing CuCN as a positive electrode catalyst. The lithium air secondary battery according to No. 3 was most excellent in cycle characteristics.

  In FIG. The initial charge-discharge curve of the lithium air secondary battery which concerns on 1-5 is shown. In the figure, “a” indicates No. using NaCN as the catalyst of the positive electrode. 1 represents a charge / discharge curve of the lithium air secondary battery according to FIG. 2 represents a charge / discharge curve of the lithium-air secondary battery according to FIG. 3 represents a charge / discharge curve of the lithium air secondary battery according to No. 3, wherein “d” is a No. 3 using AgCN. 4 represents a charge / discharge curve of the lithium-air secondary battery according to No. 4, wherein “e” is a No. 1 catalyst using no catalyst. 5 shows a charge / discharge curve of the lithium air secondary battery according to FIG.

  As shown in FIG. The lithium air secondary batteries according to Nos. The charging voltage was lower than that of the lithium air secondary battery according to No. 5.

  From the results shown in Table 1 and FIG. 3, by including a cyanide compound having high activity in generating oxygen as a positive electrode catalyst, the gas diffusivity, conductivity, wettability, etc. of the positive electrode are improved, and discharging during charging As a result of promoting the decomposition of the product, it is considered that the charging voltage is lowered and the cycle characteristics are improved.

[Example 2]
The CuCN used in [Example 1] was heat-treated at 100 ° C., 200 ° C., 300 ° C., and 400 ° C. for 5 hours in an argon atmosphere. Then, using the heat-treated CuCN as a catalyst for the positive electrode, as in [Example 1], No. 1 was used. Lithium air secondary batteries according to 6 to 9 were manufactured.
In Table 2, no. The discharge capacity in each cycle (first time, 20th time, 50th time) of the lithium air secondary battery according to 6 to 9 is shown. The discharge capacity was measured in the same manner as in [Example 1]. For comparison, No. manufactured in [Example 1] was used. The discharge capacity in each cycle of the lithium air secondary battery according to No. 3 is also shown in Table 2.

  As shown in Table 2, no. The lithium air secondary batteries according to Nos. 6 to 9 are No. The cycle characteristics were superior to those of the lithium air secondary battery according to No. 3. Among these, No. 1 was heat-treated at 200 ° C. for 5 hours. The lithium-air secondary battery according to No. 7 was most excellent in cycle characteristics. The reason for this result is considered that the moisture in the catalyst was dehydrated by the heat treatment, and the deterioration of the battery performance due to the mixing of moisture could be prevented. In addition, since the mass was reduced and the heat treatment was performed at a relatively low temperature of 200 ° C. even under the above-mentioned conditions, the dispersibility of the catalyst in the positive electrode was maintained with little influence on the crystallinity, and the effect of the catalyst was wide. It is thought that this was the reason.

[Example 3]
As a catalyst for the positive electrode, No. 2 obtained in [Example 2] with good results. No. 7, CuCN, carbon dispersed in NMP (N-methyl-2-pyrrolidone) as a volatile solvent, stirred and evaporated to dryness at 70 ° C., and polytetrafluoroethylene (PTFE) powder, Mixing was performed at a mass ratio of 5: 3: 2. And it roll-formed using the said mixture, and obtained the sheet-like electrode of thickness 0.5mm. Then, this sheet-like electrode was cut into a circle having a diameter of 23 mm. 10 was produced. And using the said positive electrode, it carried out similarly to [Example 1], and No .. 10 was manufactured.
In Table 3, no. 10 shows the discharge capacity in each cycle (first time, 20th time, 50th time) of the lithium air secondary battery according to FIG. The discharge capacity was measured in the same manner as in [Example 1]. For comparison, the No. manufactured in [Example 2] was used. The discharge capacity in each cycle of the lithium air secondary battery according to No. 7 is also shown in Table 3.

  As shown in Table 3, No. 1 using a positive electrode obtained by dispersing a catalyst in a volatile solvent and then evaporating and drying the volatile solvent. The lithium air secondary battery according to No. 10 was manufactured using no. The cycle characteristics were superior to those of the lithium air secondary battery according to No. 7. Such a result is considered to be because the dispersibility of the catalyst and carbon in the positive electrode is improved, and the effect of the catalyst is spread over a wider range.

[Example 4]
As a catalyst for the positive electrode, No. 2 obtained in [Example 2] with good results. No. 7 CuCN, carbon, and PVdF (polyvinylidene fluoride) dispersion were dispersed in NMP (N-methyl-2-pyrrolidone), which is a volatile solvent, and stirred to prepare a dispersion. And the said dispersion liquid is apply | coated on Ti mesh which is a positive electrode electrical power collector, it is made to dry at 70 degreeC, and No. 11 was produced. Similarly, applying the dispersion and drying at 70 ° C. was repeated 2 to 5 times. Positive electrodes according to 12-15 were produced. In addition, No. The positive electrodes according to 11 to 15 were pressed after being manufactured under predetermined conditions. No. manufactured Nos. 11 to 15 were used in the same manner as in [Example 1]. The lithium air secondary battery which concerns on 11-15 was manufactured.
In Table 4, no. The discharge capacity in each cycle (first time, 20th time, 50th time) of the lithium air secondary battery according to 11-15 is shown. The discharge capacity was measured in the same manner as in [Example 1]. For comparison, No. manufactured in [Example 3] was used. The discharge capacity in each cycle of the lithium air secondary battery according to No. 10 is also shown in Table 4.

  As shown in Table 4, a positive electrode was applied on a positive electrode current collector and dried. The lithium air secondary batteries according to 11 to 15 are No. The lithium-air secondary battery according to No. 10 was superior in cycle characteristics. Among these, No. manufactured by repeating the application of the positive electrode on the positive electrode current collector and drying three times. The lithium air secondary battery according to No. 13 was most excellent in cycle characteristics. Such a result was considered that the application and drying were repeated three times, and by laminating, a new and moderate three-phase interface was formed between the layers, and the performance was improved. It is done.

DESCRIPTION OF SYMBOLS 10 Lithium air secondary battery 1 Positive electrode connector 2 Electrode case 3 Positive electrode 4 Separator 5 Negative electrode 6 Negative electrode connector 7 Negative electrode support body 8 O-ring 9 Negative electrode terminal NE Nonaqueous electrolyte

Claims (8)

A positive electrode comprising a catalyst, wherein one surface is in contact with air and the other surface is in contact with a non-aqueous electrolyte;
A negative electrode comprising a substance capable of occluding and releasing at least one of metallic lithium and lithium ions,
A lithium air secondary battery configured by disposing a non-aqueous electrolyte between the positive electrode and the negative electrode,
A lithium-air secondary battery comprising a cyanide compound as the catalyst.   The lithium-air secondary battery according to claim 1, wherein the cyan compound is at least one of copper cyanide, sodium cyanide, potassium cyanide, and silver cyanide.   The lithium-air secondary battery according to claim 1 or 2, wherein the cyanide compound is a powder body heat-treated at 100 to 400 ° C. A positive electrode comprising a catalyst, wherein one surface is in contact with air and the other surface is in contact with a non-aqueous electrolyte;
A negative electrode comprising a substance capable of occluding and releasing at least one of metallic lithium and lithium ions,
A non-aqueous electrolyte is disposed between the positive electrode and the negative electrode, and a manufacturing method of manufacturing a lithium air secondary battery containing a cyanide compound as the catalyst,
A dispersion preparation step of preparing a dispersion by dispersing the cyanide compound in a volatile solvent;
After evaporating and drying the dispersion, a first positive electrode manufacturing step of forming a positive electrode by forming into a predetermined shape;
The manufacturing method of the lithium air secondary battery characterized by including. A positive electrode comprising a catalyst, wherein one surface is in contact with air and the other surface is in contact with a non-aqueous electrolyte;
A negative electrode comprising a substance capable of occluding and releasing at least one of metallic lithium and lithium ions,
A non-aqueous electrolyte is disposed between the positive electrode and the negative electrode, and a manufacturing method of manufacturing a lithium air secondary battery containing a cyanide compound as the catalyst,
A dispersion preparation step of preparing a dispersion by dispersing the cyanide compound in a volatile solvent;
Applying the dispersion onto the positive electrode current collector and drying it repeatedly 2 to 5 times to produce a positive electrode;
The manufacturing method of the lithium air secondary battery characterized by including.   6. The method for producing a lithium-air secondary battery according to claim 4, wherein the cyanide compound is at least one of copper cyanide, sodium cyanide, potassium cyanide, and silver cyanide.   The method for producing a lithium-air secondary battery according to any one of claims 4 to 6, wherein the cyanide compound is a powder body heat-treated at 100 to 400 ° C.   The apparatus provided with the lithium air secondary battery as described in any one of Claims 1-3.

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