JP2013026148A - Positive electrode for nonaqueous electrolyte lithium air secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode for a nonaqueous electrolyte lithium air secondary battery, capable of providing high coulomb efficiency (charge capacity/discharge capacity), and a method for manufacturing the positive electrode for the nonaqueous electrolyte lithium air secondary battery.SOLUTION: A positive electrode for a nonaqueous electrolyte lithium air secondary battery contains a carbon material. The carbon material is fired after acid treatment, and has an acid amount of 0.04 mmol/g or more. There is also provided a method for manufacturing the positive electrode for the nonaqueous electrolyte lithium air secondary battery.

Description

  The present invention relates to a positive electrode of a non-aqueous electrolyte lithium-air secondary battery and a method for manufacturing the same, and more specifically, by including a specific carbon material, high coulomb efficiency [ratio of initial charge capacity to discharge capacity (charge capacity) / Discharge capacity). The present invention relates to a positive electrode of a non-aqueous electrolyte lithium-air secondary battery and a method for manufacturing the same.

In recent years, the dischargeable electric capacity is large and it is easy to reduce the size and weight, and since oxygen is used from the outside, there are few resource restrictions and the environmental load is small compared to the commonly used lithium secondary battery. Water electrolyte lithium-air batteries have attracted attention and various studies have been conducted.
This non-aqueous electrolyte lithium-air battery is a battery using oxygen from the outside as a positive electrode active material, and has a positive electrode, a non-aqueous electrolyte, a separator, a negative electrode, and an oxygen diffusion layer as main components.

And in such a non-aqueous electrolyte lithium-air battery, one of the main constituents whose functions are significantly different from those of conventional lithium secondary batteries is the positive electrode, and the non-aqueous electrolyte lithium-air battery Various studies have been made on these positive electrodes.
However, in the air battery using the positive electrode of the non-aqueous electrolyte lithium-air battery according to the prior art, the coulomb efficiency is low and the secondary battery cannot be formed.
On the other hand, the carbon material contained in the positive electrode has a carbon skeleton and usually has pores on the surface, and studies have been made on improving its performance.

  For example, Patent Document 1 includes a nanoparticle-containing composite porous body including a porous body having a solid skeleton portion and pores as a porous body that can be used for a catalyst or an air battery, and further an organic aggregate such as a dendrimer. A nanoparticle-containing composite porous body is described. As a specific example, a carbon precursor gel composed of a polyphenol-based polymer as a solid skeleton portion of the porous body and a nanoparticle-containing composite porous body containing a polyamidoamine dendrimer are heat-treated at a temperature of 600 ° C. or more to remove the dendrimer. In addition, the carbon precursor is carbonized and an example of obtaining a composite porous body composed of a carbon porous body with specific values of apparent density, specific surface area, and pore diameter is shown. Not shown.

  Patent Document 2 discloses a cathode (positive electrode) for a metal-air battery, a first layer containing carbon particles not in contact with an acid, a first organic polymer, and carbon particles in contact with oxygen. A cathode is described comprising a second layer comprising a second organic polymer, wherein the first layer and the second layer are in alternating contact. As specific examples, the cathode, zinc particles, an aqueous solution of potassium hydroxide as an electrolyte, and a hole for taking in air are formed by using carbon particles obtained by heating carbon particles, nitric acid, and water under stirring. An example of obtaining a metal-air battery using a removable sheet is shown. However, zinc / air batteries are basically considered to belong to primary batteries in terms of performance.

  Patent Document 3 discloses a step of forming a liquid-containing precursor containing particulate carbon and a polymer emulsion, a step of generating droplets of a precursor aerosol from the liquid-containing precursor, and a small amount of the precursor aerosol. A method of producing particles comprising a polymer phase is described, comprising the step of heating the droplet to remove liquid from the droplet to form the particle. And it is shown that the said microparticles | fine-particles are fine particle materials, such as an electrode catalyst powder for energy device manufacture, such as a zinc-air battery and a fuel cell.

  Patent Document 4 describes a secondary air battery having oxygen as a positive electrode active material, iron and iron ions as a negative electrode active material, and having an acidic electrolyte solution. As a specific example, a secondary air battery using an acidic carbon fine powder as an acidic additive in an electrolytic solution is shown.

  Further, Patent Document 5 includes one or more transition metals of Co, Ni, and Fe, and the transition metal is supported on a carbon material as a support at a loading amount of 10 wt% to 40 wt%. Describes a lithium-air battery including a positive electrode having a catalyst having a particle diameter of 2.5 nm to 20 nm as an oxygen redox catalyst, a negative electrode having a negative electrode active material, and an ionic conductor. As a specific example, there is shown an example in which cobalt formate and a carbon material are heat-treated at 300 ° C. in a nitrogen stream to obtain a carbon material carrying 5% by weight of cobalt nanoparticles.

  Furthermore, Patent Document 6 discloses a metal-air secondary battery having an air electrode layer containing a conductive material, an air electrode having an air electrode current collector, a negative electrode layer, a negative electrode, and a nonaqueous electrolyte. A metal-air secondary battery using acicular carbon having an average aspect ratio of 10 or more is described as the conductive material. As a specific example, a metal-air secondary battery using vapor grown carbon fiber (VGCF) having an average aspect ratio of 100 is shown.

International Patent Publication No. 2004-110930 JP 2005-510929 A JP 2008-173635 A JP 2010-140736 A JP 2010-176907 A JP 2010-287390 A

However, a positive electrode of a non-aqueous electrolyte lithium-air secondary battery that can provide high coulomb efficiency (charge capacity / discharge capacity) even when a positive electrode of a non-aqueous electrolyte lithium-air battery is manufactured by applying these conventional techniques is obtained. It is not possible.
Accordingly, an object of the present invention is to provide a positive electrode of a non-aqueous electrolyte lithium-air secondary battery that can provide high coulomb efficiency (charge capacity / discharge capacity).
Moreover, the objective of this invention is providing the manufacturing method of the positive electrode of the said nonaqueous electrolyte lithium air secondary battery.

As a result of intensive studies aimed at achieving the above object, the present inventors have used a carbon material according to the prior art as a positive electrode material, so that discharge deposits (Li ₂ O ₂ ) are decomposed during charging. However, as a result of further finding out that the coulomb efficiency is low and it is difficult to make a secondary battery, the present invention has been completed.
The present invention is a positive electrode of a non-aqueous electrolyte lithium-air secondary battery containing a carbon material, wherein the carbon material is fired after acid treatment and has an acid amount greater than 0.04 mmol / g. The present invention relates to the positive electrode.

Further, the present invention is a method for producing a positive electrode of a non-aqueous electrolyte lithium air secondary battery containing a carbon material,
A step of acid-treating the porous carbon material, and a step of firing (also referred to as heat treatment) the obtained acid-treated carbon material,
It relates to the said method using the material obtained by the method containing this.
The acid amount in the present invention indicates the acid amount (mmol) per 1 g of the carbon material determined by the measurement method described in detail in the column of Examples described later.
In the present invention, the acid treatment means contacting the porous oxygen material with an acid.
Moreover, what was baked after the acid treatment in the present invention means that the acid-treated carbon material has been heat-treated.

ADVANTAGE OF THE INVENTION According to this invention, the positive electrode of the nonaqueous electrolyte lithium air secondary battery which can give high coulomb efficiency [ratio (charge capacity / discharge capacity) of the initial charge capacity and discharge capacity] can be obtained.
Further, according to the present invention, it is possible to easily obtain a positive electrode of a non-aqueous electrolyte lithium-air secondary battery that can provide high coulomb efficiency (charge capacity / discharge capacity).
In this specification, high Coulomb efficiency means that the Coulomb efficiency is 85% or more.

FIG. 1 is a graph showing the relationship between the firing temperature at the time of preparation of a carbon material, the coulombic efficiency of the battery, and the discharge capacity in a non-aqueous electrolyte lithium-air secondary battery using positive electrodes obtained in Examples and Comparative Examples. is there. FIG. 2 is a graph showing the relationship between the acid amount of the carbon material and the Coulomb efficiency of the battery in the non-aqueous electrolyte lithium-air secondary battery using the positive electrode obtained in Examples and Comparative Examples. FIG. 3 is a graph showing the relationship between the firing temperature at the time of preparation of the carbon material used in the positive electrode obtained in Examples and Comparative Examples and the acid amount of the carbon material. FIG. 4 is a schematic diagram for explaining an electrode structure of a non-aqueous electrolyte lithium-air secondary battery. FIG. 5 is a copy of a cross-sectional SEM photograph showing a state after charging in the positive electrode of the non-aqueous electrolyte lithium-air secondary battery. FIG. 6 is a schematic diagram for explaining the principle of the Coulomb efficiency of the non-aqueous electrolyte lithium-air secondary battery. FIG. 7 is a schematic view showing a carbon material manufacturing process in the embodiment of the manufacturing method of the present invention. FIG. 8 is a schematic diagram showing a process for producing a positive electrode using a carbon material in an embodiment of the production method of the present invention. FIG. 9 shows a schematic diagram of an evaluation air battery to which a positive electrode of a non-aqueous electrolyte lithium-air secondary battery is applied.

In particular, in the present invention, the following embodiments can be mentioned.
1) The positive electrode, wherein the acid amount is more than 0.04 mmol / g and less than 2 mmol / g.
2) The positive electrode further containing a binder.
3) The said manufacturing method baked at the temperature of 150 to 600 degreeC.
4) The said manufacturing method with which the said baking is performed in inert atmosphere.
5) The said manufacturing method with which the said acid treatment is performed by the contact of an inorganic acid and a porous carbon material.
6) The said manufacturing method further including the process of carrying out the temporary baking of the said acid-treated carbon material in air | atmosphere.

  In the present invention, the positive electrode of the non-aqueous electrolyte lithium-air secondary battery containing a carbon material is such that the carbon material is fired after acid treatment and the acid amount is greater than 0.04 mmol / g. A positive electrode of a non-aqueous electrolyte lithium-air secondary battery that can provide high coulomb efficiency can be obtained.

The positive electrode of the non-aqueous electrolyte lithium air secondary battery containing the carbon material, for example, as the carbon material,
A step of acid-treating the porous carbon material, and a step of firing the acid-treated carbon material,
It can obtain by using the material obtained by the method containing.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
From FIG. 1, the carbon material that can be used for the positive electrode of the air battery and can give a coulomb efficiency of 85% or more is obtained by firing an acid-treated carbon material, and the coulombic efficiency tends to decrease as the firing temperature increases. It is understood that even an acid-treated carbon material that is not fired has low Coulomb efficiency. Although the theoretical elucidation that the carbon material only treated with acid in FIG. 1 shows low Coulomb efficiency has not been made, it is considered that the trace amount of water remaining in the pores has an adverse effect on one.

Further, in the air battery positive electrode according to the embodiment of the present invention, as shown in FIG. 2, as the carbon material contained in the positive electrode, an acid-treated carbon material is baked and the acid value is 0.04 mmol / It is understood that it is necessary to achieve a Coulomb efficiency of 85% or more to be more than g, and that the coke efficiency is low if the acid value is more than 0.04 mmol / g and not fired.
Also, from FIG. 3, in order to obtain a carbon material having an acid amount greater than 0.04 mmol / g by firing the acid-treated carbon material, a temperature of 150 ° C. or more and less than 600 ° C. is suitable as the firing temperature. Is understood.

The theoretical elucidation of obtaining an air battery exhibiting high Coulomb efficiency with the positive electrode of the non-aqueous electrolyte lithium secondary battery containing the carbon material of the present invention has not yet been sufficiently made, but can be considered as follows.
First, in the nonaqueous electrolyte lithium secondary battery, as shown in FIG. 4, the product Li ₂ O ₂ is deposited on the electrode. Then generates a Li ₂ O ₂ as a product during discharge on the three-phase interface of the cathode and the electrolyte solution and the air phase, decompose the reaction product Li ₂ O ₂ during charge proceeds. For this reason, battery characteristics depend on the three-phase interface.
And in the positive electrode of the nonaqueous electrolyte lithium battery using the conventional carbon material, as shown in FIG. 5 and FIG. 6, the discharge deposit (Li ₂ O ₂ ) is not decomposed during charging, and the Coulomb efficiency is lowered. However, it was difficult to make a secondary battery.
In contrast, when a carbon material that has been baked after acid treatment in the present invention and has a higher acid content than 0.04 mmol / g is used, the COOH group causes Li exchange during oxidation in the battery reaction. Since COOH groups are present close to each other, the growth of discharge precipitates is suppressed, and the discharge precipitates can be generated in a highly dispersed state, which is considered to increase the Coulomb efficiency.

For example, as shown in FIG. 7, the carbon material in the embodiment of the present invention is a step of acid-treating a porous carbon material, and a step of firing the acid-treated carbon material at a temperature of usually 150 ° C. or higher and lower than 600 ° C. ,
Obtained by a method comprising:
The calcination temperature is preferably 175 ° C. or more and less than 600 ° C., particularly 200 ° C. or more and less than 600 ° C., among which 200 ° C. or more and 500 ° C. or less, and more preferably 200 ° C. or more and 400 ° C. or less.

The acid treatment can be usually performed by contacting an inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid and the porous carbon material in a state where the porous carbon material is dispersed in water. The contact between the inorganic acid and the porous carbon material can be performed at a temperature of room temperature to 100 ° C, preferably 50 ° C to less than 100 ° C. The contact time may be about 0.1 to 10 hours. The inorganic acid may be 0.5 to 2 mol / L in water in which the porous carbon material is dispersed as the concentration of the inorganic acid.
By the acid treatment of the carbon material, COOH or COO-M ⁺ [M: carbon material such as alkali metal such as lithium, sodium and potassium, alkaline earth metal such as magnesium and calcium, etc. It is considered that a residual component of the activation element] is generated.
After the acid treatment, the acid-treated carbon material is usually washed with water to remove the remaining acid.

The firing step can be suitably performed in an inert atmosphere, such as an Ar, N ₂ , or He atmosphere. Moreover, although the said baking process can change with temperature, it is normally 10 minutes or more, Preferably it is about 0.5 to 10 hours, It can carry out especially about 0.5 to 5 hours.
The amount of acid on the surface of the carbon material can be adjusted by the firing (heat treatment) step.
The reason for the change in the acid amount due to the firing is that the higher the temperature, the more the COOH group bonded to the carbon material is detached from the carbon material, and the COOH group is added to the carbon material by heating at a temperature around 200 ° C. .
The step of calcining the acid-treated carbon material in the atmosphere may be further added to the step.
By the acid treatment step and the firing step, a carbon material having at least a part of the porous property of the porous carbon material as a starting material and having the acid amount is obtained.

In the positive electrode of the present invention, it is essential to use a carbon material that is baked after the acid treatment and has a specific acid amount, and is usually obtained, for example, by mixing with a binder (binder).
For example, as shown in FIG. 8, the positive electrode of the present invention includes the carbon material, binder, and solvent if necessary, such as acetone, NMP having a boiling point of 200 ° C. or less, ethanol, ethanol, propanol, etc. Can be obtained by a process including mixing, roll pressing, pre-drying, cutting, and final drying.
Further, if necessary, a catalyst can be further added to the positive electrode of the present invention.

Examples of the porous carbon material which is the starting material of the carbon material in the present invention include a carbon material having a carbon skeleton and having pores on the surface. For example, a carbon element-containing compound such as a hydrocarbon is carbonized by heat treatment. And carbon particles having a hydrophobic property and having an average particle size of about 4 to 20 μm. The porous carbon material may be surface-treated but is preferably not surface-treated.
Examples of the porous carbon material include ketjen black, vulcan black, print tex, black pearl, activated carbon, acetylene black, denka black, carbon black and the like. For example, a ketjen having a specific surface area of 1270 m ² / g. Chain black EC600JD (manufactured by Lion), Ketjen black such as 800 m ² / g ketjen black EC300J (manufactured by Lion), Vulcan XC-72 (made by Cabot) having a specific surface area of 214 m ² / g, Super P ( Activated carbon) and the like may be used alone or in combination.

Examples of the binder include known materials such as PTFE, PVdF, and SBR.
Said binder may be included in the total amount of all components in an amount of 1-40% by weight, in particular 5-30% by weight.

The positive electrode of the non-aqueous electrolyte lithium-air battery of the present invention includes, for example, a current collector, such as a porous structure, such as carbon paper, carbon cloth, a metal mesh, or a non-porous body, such as a metal foil. It can be obtained by applying a slurry in which a material and a binder are dispersed in a solvent, drying, and cutting.
Further, when applying the slurry, a doctor blade method, an ink jet method or the like can be used.

  The air battery using the positive electrode of the non-aqueous electrolyte lithium-air battery according to the present invention uses, for example, a negative electrode, a separator containing a non-aqueous electrolyte, and a plurality of oxygen diffusion layer members using the positive electrode of the air battery. It can be obtained by laminating together with a fixing member in which oxygen holes are sealed.

The negative electrode may include a negative electrode layer having a negative electrode active material containing a metal as a negative electrode material species.
As the negative electrode material type, Li is preferably used because a battery having a high energy density such as Li, Na, K, Mg, Ca, Al, Zn, and Fe can be obtained.
In the case of Li, examples include Li metal, Li carbonaceous material, Li oxide, Li sulfide, and Li nitride.
The negative electrode can be prepared by a technique known per se by using a current collector, for example, any metal foil such as SUS or Ni.

The separator may include an electrolyte.
Examples of the separator include polyethylene (PE), polypropylene (PP), PP / PE / PP 1-layer to 3-layer porous membranes, nonwoven fabrics such as resin nonwoven fabrics and glass fiber nonwoven fabrics.
The electrolyte is for conducting metal ions between the negative electrode layer and the positive electrode layer. This electrolyte is a non-aqueous electrolyte that exhibits ionic conductivity in accordance with the negative electrode metal species.
Particularly, in the separator, since the positive electrode of the air battery of the present invention can provide a high discharge capacity, the electrolyte can contain an ionic liquid, and can usually contain a lithium salt together with the ionic liquid.

Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO _4, and LiAsF ₆ ; and LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _{3 and the} like.
In addition, examples of the ionic liquid include substances that are composed of only ionic molecules in which cations and anions are combined and that are liquid at room temperature (15 ° C. to 25 ° C.).

  Examples of the cation species of the ionic liquid include 2-ethylimidazolium, 3-propylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1,3-dimethylimidazolium, and the like. Imidazolium; ammonium such as diethylmethylammonium, tetrabutylammonium, cyclohexyltrimethylammonium, methyltri-n-octylammonium, triethyl (2-methoxyethoxymethyl) ammonium, benzyldimethyltetradecylammonium, benzyltrimethylammonium; and other alkylpyridiniums , Dialkylpyrrolidinium, tetraalkylphosphonium, trialkylsulfonium and the like.

Examples of the anionic species of the ionic liquid include halide anions such as Cl ⁻ , Br ⁻ and I ⁻ ; boride anions such as BF ₄ ⁻ , B (CN) ₄ ⁻ and B (C ₂ O ₄ ) ₂ ⁻ ; CN) ₂ N ⁻ , [N (CF ₃ ) ₂ ] ⁻ , [N (SO ₂ CF ₃ ) ₂ ] ^{− and the} like amide anions or imide anions; RSO ₃ ⁻ (hereinafter R is an aliphatic hydrocarbon group or aromatic Sulfate anion or sulfonate anion such as RSO ₄ ⁻ , R ^f SO ₃ ⁻ (hereinafter R ^f represents a fluorinated halogenated hydrocarbon group), R ^f SO ₄ ^−, etc .; Phosphate anions such as R ^f ₂ P (O) O ⁻ , PF ₆ ⁻ , R ^f ₃ PF ₃ ^— ; antimony anions such as SbF ₆ ; and others such as lactate, nitrate ion, trifluoroacetate, etc. The

The oxygen diffusion layer is laminated on the positive electrode and has a function of diffusing oxygen taken from the outside through oxygen holes into the positive electrode, and may be composed of, for example, an oxygen permeable membrane.
The oxygen permeable membrane preferably has a porosity of 5% to 60%. When the porosity is less than 5%, the pore space in which oxygen molecules can diffuse becomes insufficient, and the oxygen transmission rate is significantly reduced. When the porosity is larger than 60%, the strength of the film is remarkably lowered. A more optimal porosity range may be 8% or more and 50% or less.

  The oxygen diffusion layer is made of a polymer material such as polyethylene, polypropylene, poly-4-methyl-1-pentene, poly-3-methyl-1-butene, polystyrene, polymethyl methacrylate, polyvinyl chloride, nylon 6, nylon 66. , Polycarbonate, polyvinyl alcohol, polybutylene terephthalate, polyphenylene sulfide, polytetrafluoroethylene, cellulose, cellulose acetate, polyimide, and the like, which can be preferably formed from polytetrafluoroethylene.

  The form of the fixing member is not particularly limited as long as it is provided with holes. For example, the fixing member may take the form of a fibrous member, a nonwoven fabric, and a foamed material made of a metal or a carbon material. it can. Among these, it is preferable to use a fixing member composed of carbon paper or a metal mesh. From the viewpoint of easily controlling the size and distribution of holes, a metal mesh (for example, expanded metal or punching metal) is preferable. It is more preferable to use a fixing member constituted by, for example. Moreover, the fixing member provided in the positive electrode of the air battery of the present invention may be made of an insulating material. However, from the viewpoint of making it possible to provide a positive electrode for a high-performance air battery by improving the electronic conductivity, a fixing member made of a conductive material may be provided.

The fixing member is provided with a plurality of oxygen holes (also referred to as air holes) for taking oxygen into the positive electrode.
The oxygen holes are usually in the range of 0.1 to 3 mm in diameter, preferably in the range of 0.3 to 1 mm, for example, a plurality of through holes having a diameter of 0.5 mm as many as possible, for example, about 5 to 10 pieces. A through hole may be provided in the fixing member.

The non-aqueous electrolyte lithium-air battery can be manufactured by laminating and stacking the above-described members, but even if a water-repellent film is laminated to prevent the introduction of moisture from the outside. Good.
In the air battery, the introduced oxygen may be oxygen in dry air, but may be pure oxygen.

Examples of the present invention will be described below.
The following examples are for illustrative purposes only and are not intended to limit the invention.
In each of the following examples, the measurement of the carbon material and the evaluation of the battery were performed by the measurement methods described below. In addition, the following measurement is an illustration and the measuring method considered by those skilled in the art to be equivalent can be used similarly.

Measurement of acid amount Weigh 0.5 g of sample (n = 2), add 20 mL of 0.1 N NaOH aqueous solution, add ultrasonic waves for 20 minutes, filter (filter paper: No. 5C), take 5 mL, 40 mL of pure water was used as a solvent, and neutralization titration was performed with 0.1 M HCl using an automatic titrator.
Automatic titrator conditions: Standard File (Acid-Ba, mV-HCl)

Charge / Discharge Evaluation Method Charge / Discharge Tester: Nagano Charge / Discharge Device (BTS2004H)
Current density: 0.05 mA / cm ²
Discharge start voltage: 2.0V
Charge starting voltage: 3.8V
Measurement temperature: 60 ° C

Example 1
Super P (manufactured by TIMCAL, characteristics: hydrophobic, average particle size: 5 μm) was used as the porous carbon material, and acid treatment was performed at 70 ° C. for 1 hour with 1 mol / L nitric acid according to the process shown in FIG. Next, after rinsing with water, the obtained acid-treated carbon material was calcined at 120 ° C. for 12 hours (temperature increase rate: 10 ° C./min) in an air atmosphere, and then at 200 ° C. for 2 hours in an Ar atmosphere ( (Temperature increase rate: 10 ° C./min)
The acid amount of the carbon material fired after the acid treatment was measured. The acid amount was 1.06 mmol / g. In addition, the specific surface area measured by the conventional method about the obtained carbon material was 101 m < ² > / g, and it was confirmed that it is a porous carbon material.

Using the obtained carbon material fired after the acid treatment, the carbon material (90% by mass) and the binder (PTFE, 10% by mass) are mixed and pelletized according to the process shown in FIG. Produced.
Using the positive electrode obtained, a discharge evaluation cell having a cross-sectional structure shown in FIG. 9 was produced under the following cell conditions.
Negative electrode: metallic lithium (thickness: 200 μm, φ15 mm)
Electrolyte: PP13-TFSA / 0.32 mol / kg Li-TFSA
Separator: Polypropylene nonwoven fabric (JH1004N)
Cell: F-type cell (Hokuto Denko)
Container: Glass desiccator with gas replacement cock (500 mL)
Gas: Oxygen, Argon Evaluation was performed using the obtained discharge evaluation cell. The obtained results are shown together with other results in FIG. 1, FIG. 2, and FIG.

Comparative Example 1
The amount of acid was measured for the carbon material that was dried at room temperature without firing after the acid treatment. The acid amount was 0.90 mmol / g.
A positive electrode was produced in the same manner as in Example 1 except that the carbon material that was not subjected to the firing treatment after the acid treatment was used.
A discharge evaluation cell was fabricated in the same manner as in Example 1 except that the obtained positive electrode was used.
Evaluation was performed using the obtained discharge evaluation cell. The obtained results are shown together with other results in FIG. 1 and FIG.

Example 2
Acid treatment and calcination were performed in the same manner as in Example 1 except that the calcination temperature was changed from 200 ° C. to 400 ° C. (temperature increase rate: 10 ° C./min).
The acid amount of the carbon material fired after the acid treatment was measured. The acid amount was 0.08 mmol / g.
A positive electrode was produced in the same manner as in Example 1 except that the carbon material fired after the acid treatment was used.
A discharge evaluation cell was fabricated in the same manner as in Example 1 except that the obtained positive electrode was used.
Evaluation was performed using the obtained discharge evaluation cell. The obtained results are shown together with other results in FIG. 1, FIG. 2, and FIG.

Comparative Examples 2-3
Example except that the temperature of the main firing was changed from 200 ° C. to 600 ° C. (temperature increase rate: 10 ° C./min) (Comparative Example 2) or 800 ° C. (temperature increase rate: 10 ° C./min) (Comparative Example 3) In the same manner as in No. 1, acid treatment and baking were performed.
The acid amount of the carbon material fired after the acid treatment was measured. The acid amount was less than 0.01 mmol / g.
A positive electrode was produced in the same manner as in Example 1 except that the carbon material fired after the acid treatment was used.
A discharge evaluation cell was fabricated in the same manner as in Example 1 except that the obtained positive electrode was used.
Evaluation was performed using the obtained discharge evaluation cell. The obtained results are shown together with other results in FIG. 1, FIG. 2, and FIG.

From FIG. 1 and FIG. 2, when the acid-treated carbon material is calcined as the carbon material contained in the positive electrode and the acid value is more than 0.04 mmol / g, it is possible to achieve a Coulomb efficiency of 85% or more. It has been shown.
Further, FIG. 3 shows that a carbon material having an acid amount greater than 0.04 mmol / g can be easily obtained by firing the acid-treated carbon material at 200 ° C. or 400 ° C.

  With the positive electrode of the present invention, a high Coulomb efficiency of 85% or more [the ratio between the initial charge capacity and the discharge capacity (charge capacity / discharge capacity) is shown. The positive electrode of the non-aqueous electrolyte lithium-air secondary battery can be obtained.

Claims (8)

  A positive electrode of a non-aqueous electrolyte lithium-air secondary battery containing a carbon material, wherein the carbon material is fired after acid treatment and has an acid amount greater than 0.04 mmol / g. The positive electrode.   The positive electrode according to claim 1, wherein the acid amount is greater than 0.04 mmol / g and less than 2 mmol / g.   Furthermore, the positive electrode of Claim 1 or 2 containing a binder. A method for producing a positive electrode of a non-aqueous electrolyte lithium air secondary battery containing a carbon material, the carbon material,
A step of acid-treating the porous carbon material, and a step of firing the obtained acid-treated carbon material,
Said method using the material obtained by the method containing this.   The manufacturing method according to claim 4, wherein baking is performed at a temperature of 150 ° C. or higher and lower than 600 ° C.   The method according to claim 4 or 5, wherein the firing is performed in an inert atmosphere.   The manufacturing method according to any one of claims 4 to 6, wherein the acid treatment is performed by contact between an inorganic acid and a porous carbon material.   The manufacturing method of any one of Claims 4-7 which further includes the process of pre-baking the said acid-treated carbon material in air | atmosphere.