JP6813852B2 - Positive electrode for aluminum secondary battery and aluminum secondary battery - Google Patents

Description

The present invention relates to a novel positive electrode that can be used in an aluminum secondary battery, and an aluminum secondary battery that includes the positive electrode.

Aluminum has a high electric capacity per unit volume and mass, and in particular, has a theoretical energy density equivalent to about four times that of lithium on a volume basis. In addition, it has a large elemental abundance ratio and can be easily obtained at low cost. Therefore, if aluminum or an aluminum alloy can be used as the negative electrode of the battery, a battery having a high energy density can be realized at low cost. For this reason, aluminum secondary batteries are one of the promising batteries in the future.

Patent Document 1 discloses an aluminum secondary battery in which an aluminum halide-based ionic liquid is used as an electrolytic solution and activated carbon or the like is used as a positive electrode in order to improve charging efficiency, but materials that can be used as a positive electrode are limited. There was also a problem that the positive electrode capacity was not sufficient.

Japanese Unexamined Patent Publication No. 2014-222609

The present invention is intended to provide a positive electrode for an aluminum secondary battery capable of enhancing discharge voltage, discharge capacity, Coulomb efficiency and cycle characteristics, and an aluminum secondary battery using the positive electrode.

As a result of diligent studies to solve the above problems, the present inventors have observed significant deterioration of the positive electrode, which is considered to be caused by insertion of anions between the graphite layers, when graphite is used for the positive electrode, and the deterioration is the positive electrode. We have found that this can be prevented by using a nanocarbon material as an active material and using a predetermined binder, and further studies have been carried out to complete the present invention.

That is, the present invention
[1] A positive electrode for an aluminum secondary battery, which comprises an active material which is a nanocarbon material and a binder which is stable to Lewis acid.
[2] The binder is at least one selected from the group consisting of a polyether polymer, a polymer which is an alginic acid or an alginic acid derivative, a polymer which is a polyamic acid derivative, and a polymer which is a cellulose derivative. [1] The positive electrode for an aluminum secondary battery,
[3] The aluminum secondary according to the above [1], wherein the binder is at least one selected from the group consisting of polysulfone, polyethersulfone, alginic acid, sodium alginate, ammonium alginate, propylene glycol alginate, polyimide, and carboxymethyl cellulose. Positive electrode for batteries,
[4] Any of the above [1] to [3], wherein the nanocarbon material is at least one selected from the group consisting of carbon nanotubes, carbon nanohorns, fullerenes, carbon nanofibers, and single-walled or multilayer graphene. The positive electrode for aluminum secondary battery according to item 1.
[5] The aluminum according to any one of the above [1] to [4], wherein the weight ratio of the nanocarbon material to the binder (nanocarbon material: binder) is in the range of 50:50 to 90:10. Positive electrode for secondary battery,
[6] An aluminum secondary battery comprising the positive electrode for an aluminum secondary battery according to any one of the above [1] to [5].
[7] electrolyte AlX ₄ ^- (where, X is Cl, a halogen selected from the group consisting of Br and I, 4 single X contained in one molecule are the same or different.) Include The aluminum secondary battery according to the above [6], which is made of.
[8] The aluminum secondary battery according to the above [6] or [7], wherein the electrolytic solution is an ionic liquid which is a non-aqueous solvent in which the above AlX ₄ ^- is dissolved.
[9] Any one of the above [6] to [8], wherein the cation of the ionic liquid is at least one selected from the group consisting of imidazolium, pyridinium, pyrrolidinium, piperidinium, tetraalkylammonium, pyrazolium, and phosphonium. The aluminum secondary battery according to item 1.
[10] The aluminum secondary battery according to any one of [6] to [9] above, wherein the negative electrode is aluminum or an aluminum alloy.
Regarding.

According to the present invention, it is possible to provide a positive electrode for an aluminum secondary battery capable of increasing the discharge voltage, discharge capacity, and Coulomb efficiency, and an aluminum secondary battery using the positive electrode. Further, the aluminum secondary battery does not require a rare metal and is excellent in terms of resource procurement, and is very useful in recent years when the price of a rare metal is soaring.

Further, according to the present invention, it is possible to provide a positive electrode for an aluminum secondary battery capable of enhancing cycle characteristics and an aluminum secondary battery using the positive electrode. Here, the cycle characteristic refers to the characteristic of a secondary battery whose charge / discharge capacity decreases with repeated charging / discharging. A secondary battery having a small decrease in charge / discharge capacity is a secondary battery having excellent cycle characteristics, and a secondary battery having a large decrease in charge / discharge capacity is a secondary battery having inferior cycle characteristics.

It is a drawing substitute photograph which showed the positive electrode (2) (GNP _{5 μm} : polysulfone = 70:30) used in an Example. It is a drawing substitute photograph which showed the positive electrode (5) (GNP _{5 μm} : sodium alginate = 70:30) used in an Example. It is a schematic diagram of the aluminum secondary battery which concerns on embodiment of this invention. It is a figure which showed the relationship between the discharge capacity and the number of cycles when the charge / discharge test was repeated about the aluminum secondary battery of Example 1 (polysulfone) and Example 6 (polyimide). It is a result of observing the state of the positive electrode surface of the aluminum secondary battery of Example 6 with a scanning electron microscope before the start of the charge / discharge test and at the time of the tenth cycle. It is a figure which showed the relationship between the charge capacity and the discharge capacity, and the number of cycles when the charge / discharge test was performed while changing the discharge rate as shown in Table 6 about the aluminum secondary battery of Example 6.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to this, and various modifications are possible.

The aluminum secondary battery of the present embodiment is provided with a pair of electrodes, and an electrolytic solution exists between the electrodes, and a binder stable to an active material which is a nanocarbon material and Lewis acid is used for the positive electrode thereof. It is characterized by that. Hereinafter, the configuration of the aluminum secondary battery will be described.

<Negative electrode>
The negative electrode is not particularly limited as long as it enables precipitation / melting of aluminum or dealloying / alloying reaction of aluminum ions from an aluminum alloy, but a negative electrode material suitable for such a purpose is, for example, a metal. Examples include aluminum or aluminum alloys such as Al-Mn and Al-Mg.

<Electrolytic solution>
As an electrolytic solution, AlX ₄ ^- (symbol X have the same meanings as defined above.) Can be used an electrolyte comprising a. When the electrolytic solution is used, the halogen reaction can be utilized for the positive electrode reaction. That is, in order to utilize aluminum for the negative electrode reaction, it is necessary to precipitate and dissolve aluminum, but since the redox potential of aluminum is as low as -1.66V based on the standard hydrogen electrode, it is used in a non-aqueous solvent system. The following reactions (1) to (4) are used.

（記号Ｘは、前記と同一意味を有する。）

(The symbol X has the same meaning as described above.)

The redox reaction represented by the formula 1 is an Al precipitation / dissolution reaction, and usually proceeds at a Coulomb efficiency of 100%. This reaction is the negative electrode reaction of the aluminum secondary battery. On the other hand, the redox reaction represented by the formulas 2 to 4 is the positive electrode reaction.

The total reaction formula of the secondary battery system of the present invention is represented by the following formulas 5 to 7.

（記号Ｘは、前記と同一意味を有する。）

(The symbol X has the same meaning as described above.)

AlX ₄ ^- In, X is a halogen selected from the group consisting of Cl, Br and I, 4 single X contained in one molecule are the same or different. That, AlX ₄ ^- Multiple may be composed of halogen species, AlX ₄ ^-, for ^{_{example, AlCl 4 -, AlBr 4 -}} , AlI 4 -, AlClBr 3 -, AlClI 3 -, AlCl 2 BrI -, AlClBr ₂ I ^-, AlClBrI ₂ ^- a may be, may they be mixed.

The non-aqueous solvent, AlX ₄ in the electrolyte solution ^- it is not limited as long as it can cause, high ionic conductivity, low volatility, an ionic liquid has the feature such as high thermal stability Is preferable. As a result, the aluminum secondary battery is less likely to malfunction. The term "ionic liquid" as used herein means a salt that exists as a liquid even at room temperature. Examples of the cation of this ionic liquid include imidazolium, pyridinium, pyrrolidinium, piperidinium, tetraalkylammonium, pyrazolium, phosphonium and the like.

Examples of the imidazolium include 1-ethyl-3-methylimidazolium (C ₂ mim ⁺ ), 1-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, and 1-allyl-. Examples thereof include 3-methylimidazolium, 1-allyl-3-ethylimidazolium, 1-allyl-3-butylimidazolium, and 1,3-diallyl imidazolium.

Examples of the pyridinium include 1-propylpyridinium, 1-butylpyridinium, 1-ethyl-3- (hydroxymethyl) pyridinium, 1-ethyl-3-methylpyridinium and the like.

Examples of the pyrrolidinium include N-methyl-N-propylpyrrolidinium, N-methyl-N-butylpyrrolidinium, N-methyl-N-methoxymethylpyrrolidinium and the like.

In addition, examples of the piperidinium include N-methyl-N-propyl piperidinium and the like.

Further, examples of the tetraalkylammonium include N, N, N-trimethyl-N-propylammonium, methyltrioctylammonium and the like.

Examples of the pyrazolium include 1-ethyl-2,3,5-trimethylpyrazolium, 1-propyl-2,3,5-trimethylpyrazolium, and 1-butyl-2,3,5-trimethyl. Pyrazolium and the like can be mentioned.

The cations can be used alone or in combination of two or more.

Examples of the anion constituting the ionic liquid in combination with the cationic, in terms of reversibility and energy storage capability of the cathode reaction, AlCl ₄ ^-, AlBr ₄ ^- and AlI ₄ ^- are preferred. Anions can be used alone or in combination of two or more.

AlX ₄ in the electrolyte solution ^- increasing the concentration of, from the viewpoint of improving the capacity of the secondary battery, the ratio of AlX ₃ in the electrolytic solution is preferably at least 50 mol%, or less 66.7mol%. From the viewpoint of providing a high aluminum secondary battery of utility, particularly, AlX ₄ ^- is AlCl ₄ ^- or AlBr ₄ ^- a is (in this case, AlX ₃ is AlCl ₃ or AlBr _3), the non-aqueous solvent It is preferably 1-ethyl-3-methylimidazolium bromide or 1-ethyl-3-methylimidazolium chloride.

The electrolytic solution may contain a non-aqueous solvent other than the above-mentioned non-aqueous solvent. Other non-aqueous solvents, for example, commonly is the non-aqueous solvent and a cation, _{^{anion, BF 4 -, NO 3 -}} , PF 6 -, SbF 6 -, CH 3 CH 2 OSO 3 -, CH 3 CO _{^{2 -, (FSO 2) 2N-}} [ bis (fluoro sulfonyl) imide anion, or ionic liquids include fluoroalkyl group-containing anionic. Further, a compound may be added to the electrolytic solution. For example, urea, lithium chloride, sodium chloride, potassium chloride, calcium chloride, magnesium chloride and the like can be mentioned.

Examples of the fluoroalkyl group-containing anions such as, CF ₃ CO ₂ ^-, perfluoroalkyl sulfonyl group-containing anion, and the like. Examples of the perfluoroalkyl sulfonyl group-containing anions such ^{_{as, CF 3 SO 3 -, (}} CF 3 SO 2) 2N- [ bis (trifluoromethylsulfonyl) _{imide], (CF 3 SO 2)} 3 C- or the like is exemplified Will be done.

<Positive electrode>
(Active material)
For the positive electrode, a nanocarbon material is used as the active material. Here, the nanocarbon material is a nanomaterial typified by carbon nanotubes, carbon nanohorns, fullerenes, carbon nanofibers, and single-layer or multi-layer graphene, and the walls constituting these are monolayer to several tens of layers. It is characterized by being a graphene sheet. The thickness of the wall is not particularly limited as long as it exhibits characteristics as a nanocarbon material such as good electrical conductivity and thermal conductivity, and also exhibits flexibility for insertion of anions into graphene layers. However, the preferable range is, for example, about 20 nm or less, more preferably about 15 nm or less, still more preferably about 10 nm or less. The lower limit of the wall thickness is not particularly limited, and may be 0.335 nm, which is the thickness of one graphene sheet layer.

Among the above-mentioned nanocarbon materials, multi-layer graphene is preferable from the viewpoint of easy availability and handling, and the shape thereof is preferably scaly. The size of the scaly multilayer graphene is, for example, 3 to 30 μm in width, preferably 5 to 25 μm, and 3 to 30 μm in length, preferably 5 to 25 μm. Within such a range, the stress change that occurs when the anion is inserted between the graphene layers can be further relaxed. Specific examples of scaly multilayer graphene include Strem Chemicals, Inc. Graphene nanoplatelets made by.

(binder)
The binder is not particularly limited as long as it is a binder stable to Lewis acid in the electrolytic solution, and specific examples of such a binder include polyether polymers such as polysulfone and polyethersulfone, as well as alginic acid. , Polymers that are alginic acid derivatives such as sodium alginate, ammonium alginate, and propylene glycol alginate, polymers that are polyamic acid derivatives such as polyimide, and polymers that are cellulose derivatives such as carboxymethyl cellulose. Of these, polyether polymers such as polysulfone, polymers that are alginic acid derivatives such as sodium alginate, and polymers that are polyamic acid derivatives such as polyimide are preferable. Examples of the polysulfone include polysulfone (CAS number: 25135-51-7; number average molecular weight (Mn) to 22,000) available from SIGMA-ALDRICH. Examples of sodium alginate include sodium alginate available from Chimica Co., Ltd. As polyimide, Ai Co., Ltd. S. A dream bond available from Tay is pre-dried and heat-vacuum polymerized.

When the binder is blended, the blending ratio is the active material: binder (weight ratio), preferably in the range of 50:50 to 90:10, more preferably in the range of 60:40 to 80:20, and even more preferably. Is in the range of 65: 35 to 75:25, most preferably about 70: about 30. In this case, "about" means to allow an error of ± 3%, preferably ± 2%, and more preferably ± 1%. If the amount of the binder is less than 50% by weight, the active material tends to deteriorate mainly during charging during repeated charging and discharging. On the other hand, if the amount of the binder is more than 90% by weight, the amount of the active material is small, and there is a tendency that sufficient performance as a battery cannot be exhibited.

The electrode using these active materials and the binder may adopt a known constitution, and if desired, a conductive auxiliary agent, a thickener, or the like may be further blended. Examples of the conductive auxiliary agent include carbons such as carbon black, acetylene black, and Ketjen black, graphite, and metals. Further, examples of the thickener include carboxymethyl cellulose and ethylene glycol.

(Current collector)
Examples of the current collector used for the electrode include platinum, molybdenum, nickel, and copper. Its tip is usually used in the form of foil.

(Other battery components)
In addition, an apparatus configuration for constructing an aluminum secondary battery, for example, a separator installed between the positive electrode and the negative electrode to prevent short-circuiting of both electrodes, a battery container, etc., is used for a known secondary battery, if desired. The configured configuration can be diverted. Examples of the separator include glass fiber, fluoropolymer-based, polyethylene-based and polypropylene-based separators. The fluoropolymer-based separator has uniform pores, makes the precipitation of Al by the negative electrode uniform in the present aluminum secondary battery, and contributes to the stable operation of the aluminum secondary battery.

<Aluminum secondary battery>
The type of the aluminum secondary battery is not particularly limited, and examples thereof include a cylindrical type, a coin type, a button type, and a laminated type.

The aluminum secondary battery of the present invention can be produced according to a conventional method by using a negative electrode, an electrolyte, and, if desired, a member such as a separator for the positive electrode.

For the positive electrode, a particulate positive electrode active material is mixed with a binder and, if desired, other components and a solvent to prepare a paste-like positive electrode material, the positive electrode material is applied to a current collector, dried, and desired. It can be produced by crimping with. As another method, for example, the positive electrode is obtained by kneading the positive electrode active material together with a binder, other components if desired, and a small amount of solvent in a mortar or the like to form a film, and then collecting the positive electrode using a press or the like. It can also be produced by crimping to an electric body. Examples of the solvent include dichloromethane, acetone, N-methyl-2-pyrrolidone, N, N-dimethylformaldehyde, alcohol, water and the like. One kind or two or more kinds of these solvents can be used.

The coating amount of the current collector of the positive electrode material is preferably in the range of 0.2~1.4mg / cm ^2, more preferably 0.3~1.0mg / cm ² range, more preferably 0 It is in the range of 4 to 0.8 mg / cm ² . When the coating amount is within the above range, the capacity tends to increase.

Although the present invention will be described based on examples, the present invention is not limited to the examples.

The materials used in this specification are summarized below. Each material was purified according to a conventional method as needed.

<Materials used in the test>
Graphene nanoplatelets: Strem Chemicals, Inc. Available from the company, thickness 6-8 nm, width 5 μm and 25 μm
Polysulfone: available from SIGMA-ALDRICH, number average molecular weight (Mn) to 22,000 (measured by membrane osmometer), bead polyimide: Eye Co., Ltd. S. After pre-drying the dream bond available from Tay (temperature: 100 ° C, pressure: 1 Pa, time: 12 hours), it is synthesized by polymerization by heating vacuum (temperature: 300 ° C, pressure: 1 Pa, time: 5 hours). ..
Sodium alginate: Available from Chimica Co., Ltd., I-1G
Dichloromethane: Available from Wako Pure Chemical Industries, Ltd., Special grade acetone: Available from Wako Pure Chemical Industries, Ltd., Special grade aluminum (Al) coil: Available from Niraco Co., Ltd., Diameter 1 mm, Purity 99.999% Glass filter: Available from Ace Glass, G4
AlCl ₃ : Available from SIGMA-ALDRICH, anhydrous ≥99.0%
1-Ethyl-3-methylimidazolium chloride ([C ₂ mim] Cl): Obtained from Tokyo Chemical Industry Co., Ltd. Sulfuric acid: Available from Wako Pure Chemical Industries, Ltd., Special grade phosphoric acid: Wako Pure Chemical Industries, Ltd. ), Special grade nitric acid: Available from Wako Pure Chemical Industries, Ltd., Special grade ultrapure water: Purified by Milli-Q system Grade A 10 (Millipore)

Test (1)
<Manufacturing of aluminum secondary battery>
(Positive electrode)
(1) Nanocarbon material electrode using polysulfone as a binder Graphene nanoplatelets (GNP _{5 μm} ) with a width of 5 _μm and polysulfone are added to dichloromethane at 90:10, 70:30, and 50:50 weight ratios, and sonicated. After stirring with, acetone was added and allowed to stand to prepare a positive electrode material. On the other hand, a molybdenum plate current collector whose upper part is covered with Teflon (registered trademark) tape in order to secure a lead wire spot portion in advance and to make the exposed area 1.0 cm ² (length 1.0 cm, width 1.0 cm). A body (available from Nirako Co., Ltd., 99.95%, thickness 0.1 mm) was prepared, and a positive electrode material was applied to the exposed surface (application amount: 0.7 mg). After the coating material was dried to remove the solvent, it was pressure-bonded to the current collector at 30 kN using a hydraulic press. A platinum wire was spot-welded to the current collector thus obtained as a lead wire, and the positive electrode (1) (GNP _{5 μm} : polysulfone = 90:10) and the positive electrode (2) (GNP _{5 μm} : polysulfone = 70:30) ( FIG. 1) and the positive electrode (3) (GNP _{5 μm} : polysulfone = 50: 50).

Graphene nanoplatelets (GNP _{25 μm} ) with a width of 25 _μm and polysulfone were treated in the same manner as above at a weight ratio of 90:10 to prepare positive electrodes (4) (GNP _{25 μm} : polysulfone = 90:10).

(2) Nanocarbon material electrode using sodium alginate as a binder Graphene nanoplatelets (GNP _{5 μm} ) with a width of 5 _μm and sodium alginate are added to ultrapure water at a weight ratio of 70:30, kneaded in a dairy pot, and allowed to stand. , As a positive electrode material. Using the positive electrode material, a positive electrode (5) (GNP _{5 μm} : sodium alginate = 70:30) was prepared by treating in the same manner as described above (FIG. 2).

(Negative electrode)
An aluminum (Al) coil was used as the negative electrode. The Al coil is sufficiently immersed in a mixed acid for cleaning Al (a mixture of 100 mL of sulfuric acid, 121 mL of phosphoric acid, and 29 mL of nitric acid) before use, and washed with ultrapure water using an ultrasonic cleaner (USM of AS ONE). After that, it was dried with a vacuum dryer (VOS-300SD of Tokyo Science Instruments Co., Ltd.) before use.

(Reference pole)
As the reference electrode, an Al (III) / Al electrode in which an aluminum wire was immersed in an electrolytic solution partitioned by a glass filter was used.

(Electrolytic solution)
In a glove box (VAC NEXUS II SYSTEM, H ₂ O <1 ppm, O ₂ <1 ppm) in an argon atmosphere, AlCl ₃ and [C ₂ mim] Cl are mixed so as to have a molar ratio of 3: 2. , 60.0-40.0 mol% AlCl _3- [C ₂ mim] Cl ionic liquid was prepared. After the preparation, constant current electrolysis (5 mA, 72 hours) was performed using the Al coil electrode as a cathode and an anode to electrochemically remove a small amount of impurity ions and water present in the bath, and this was used as an electrolytic solution.

(Aluminum secondary battery)
Using the positive electrode, the negative electrode, the reference electrode, and the electrolytic solution, a cylindrical three-electrode cell was produced in a glove box having an argon atmosphere according to Table 1, and used as an aluminum secondary battery. A schematic diagram of an aluminum secondary battery according to an embodiment of the present invention is shown in FIG.

正極（１） ＧＮＰ_5μm：ポリスルホン＝９０：１０
正極（２） ＧＮＰ_5μm：ポリスルホン＝７０：３０
正極（３） ＧＮＰ_5μm：ポリスルホン＝５０：５０
正極（４） ＧＮＰ_25μm：ポリスルホン＝９０：１０
正極（５） ＧＮＰ_5μm：アルギン酸ナトリウム＝７０：３０

Positive electrode (1) GNP _{5 μm} : polysulfone = 90:10
Positive electrode (2) GNP _{5 μm} : Polysulfone = 70:30
Positive electrode (3) GNP _{5 μm} : Polysulfone = 50:50
Positive electrode (4) GNP _{25 μm} : polysulfone = 90:10
Positive electrode (5) GNP _{5 μm} : Sodium alginate = 70:30

<Evaluation>
The aluminum secondary batteries of Examples 1 to 5 were subjected to a charge / discharge test under the conditions of a cutoff voltage (upper limit: 2.1 V; lower limit: 0.8 V) and a temperature of 25 ° C. The discharge voltage and discharge capacity of the first cycle, and the Coulomb efficiency (definition: discharge capacity / charge capacity × 100) were determined, respectively. All electrochemical measurements were performed in a glove box with an argon atmosphere using a potentiostat / galvanostat (Compact Stat manufactured by IVIUM) or a charging / discharging device (Hokuto Denko Co., Ltd., HJ-1001SD8) ( The same shall apply hereinafter unless otherwise specified). The results are shown in Table 2.
<Result>

From the above, the aluminum secondary battery according to the embodiment of the present invention does not decrease in discharge capacity even at a high discharge rate. In addition, the Coulomb efficiency also clears the excellent value. Therefore, the positive electrode according to the present invention exhibits excellent electrode characteristics, and the aluminum secondary battery using the electrode exhibits excellent characteristics in discharge voltage, discharge capacity, and Coulomb efficiency.

Test (2)
<Manufacturing of aluminum secondary battery>
Treated in the same manner as in "Preparation of aluminum secondary battery" in test (1), except that polyimide was used instead of polysulfone as the binder and the weight ratio of graphene nanoplatelets to polyimide was as shown in Table 3. The aluminum secondary batteries shown in Table 3 according to the examples were obtained.

<Evaluation>
The aluminum secondary batteries of Examples 1 and 6 were subjected to a charge / discharge test under the conditions of a cutoff voltage (upper limit: 2.4 V; lower limit: 0.8 V) and a temperature of 25 ° C.

<Result>
The discharge voltage and discharge capacity of the 10th cycle, and the Coulomb efficiency (definition: discharge capacity / charge capacity × 100) were determined, respectively. The results are shown in Table 4.

The discharge voltage and discharge capacity of the 1000th cycle, and the Coulomb efficiency (definition: discharge capacity / charge capacity × 100) were determined, respectively. The results are shown in Table 5. Further, FIG. 4 shows the relationship between the discharge capacity and the number of cycles during this period. Further, with respect to the positive electrode of Example 6, the results of observing the state of the positive electrode surface before the start of the test and in the 100th cycle with a scanning electron microscope are shown in FIG. From FIG. 5, it can be seen that even after 100 cycles, almost no change such as peeling is observed on the surface of the positive electrode.

From the above, the aluminum secondary battery according to the embodiment of the present invention exhibits an extremely excellent feature that the discharge capacity does not decrease even at a high discharge rate and the charge / discharge can be performed for 1000 cycles or more. Therefore, the positive electrode according to the present invention exhibits excellent electrode characteristics, and the aluminum secondary battery using the electrodes exhibits excellent characteristics in discharge voltage, discharge capacity, Coulomb efficiency, and cycle characteristics.

Test (3)
<Evaluation>
A charge / discharge test was performed on the aluminum secondary battery of Example 6 under the conditions of a cutoff voltage (upper limit: 2.4 V; lower limit: 0.8 V) and a temperature of 25 ° C. while changing the discharge rate as shown in Table 6. It was.

<Result>
The results are shown in FIG. It has been shown that the discharge capacity decreases as the discharge rate increases from 1000 mAhg ^-1 to 10000 mAhg ^-1 , but when the discharge rate is returned to 1000 mAhg ^-1 , the discharge capacity also returns to almost the original value.

According to the present invention, it is possible to provide a positive electrode for an aluminum secondary battery capable of enhancing discharge voltage, discharge capacity, Coulomb efficiency and cycle characteristics, and an aluminum secondary battery using the positive electrode.

1 Aluminum secondary battery 11 Positive electrode 12 Mo current collector 13 Pt current collector 14 Negative electrode 15 Reference electrode 16 Electrolyte

Claims (9)

A positive electrode for an aluminum secondary battery, which comprises an active material which is a nanocarbon material and a binder which is stable to Lewis acid .
A positive electrode for an aluminum secondary battery, wherein the binder is at least one selected from the group consisting of polysulfone, polyethersulfone, alginic acid, sodium alginate, ammonium alginate, propylene glycol alginate, polyimide, and carboxymethyl cellulose . Binder, polysulfone, sodium A alginic acid, is at least one selected from the port Riimi de or Ranaru group, a positive electrode for aluminum secondary battery according to claim 1, wherein. The positive electrode for an aluminum secondary battery according to claim 1 or 2 , wherein the nanocarbon material is at least one selected from the group consisting of carbon nanotubes, carbon nanohorns, fullerenes, carbon nanofibers, and single-walled or multilayer graphene. .. The positive electrode for an aluminum secondary battery according to any one of claims 1 to 3 , wherein the weight ratio of the nanocarbon material to the binder (nanocarbon material: binder) is in the range of 50:50 to 90:10. An aluminum secondary battery comprising the positive electrode for an aluminum secondary battery according to any one of claims 1 to 4 . Electrolyte AlX ₄ ^- (where, X is Cl, a halogen selected from the group consisting of Br and I, 4 single X contained in one molecule are the same or different.) Those comprising The aluminum secondary battery according to claim 5 . The aluminum secondary battery according to claim 5 or 6 , wherein the AlX ₄ ^- is dissolved in an ionic liquid in which the electrolytic solution is a non-aqueous solvent. The aluminum according to any one of claims 5 to 7 , wherein the cation of the ionic liquid is at least one selected from the group consisting of imidazolium, pyridinium, pyrrolidinium, piperidinium, tetraalkylammonium, pyrazolium, and phosphonium. Secondary battery. The aluminum secondary battery according to any one of claims 5 to 8 , wherein the negative electrode is aluminum or an aluminum alloy.

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