JP2020017351A - Positive electrode material for zinc ion battery - Google Patents

Abstract

To provide a novel positive electrode material for a zinc ion battery.SOLUTION: Spinel-type lithium manganate known as a positive electrode material for a lithium ion battery or a dissimilar metal substitute of the same is found that zinc ions can be inserted and removed. That is, the positive electrode material for a zinc ion battery has a spinel-type crystal phase containing lithium, manganese, and oxygen.SELECTED DRAWING: Figure 2

Description

  The present application discloses a positive electrode material and the like used for a zinc ion battery.

As disclosed in Non-Patent Document 1, α-MnO ₂ is known as a positive electrode material of a zinc ion battery. The zinc ion battery disclosed in Non-Patent Document 1 utilizes a conversion reaction between α-MnO ₂ and H ⁺ .

Huilin Pan et al., Nature Energy, 2016, 1, 16039

  The zinc ion battery has a problem that there are few choices of a positive electrode material. There is a need for a new positive electrode material capable of electrochemically inserting and removing zinc ions.

  The present application discloses a positive electrode material for a zinc ion battery having a spinel-type crystal phase containing lithium, manganese, and oxygen as one of means for solving the above problems.

  According to the inventor's new knowledge, a spinel-type composite oxide containing lithium and manganese is obtained by desorbing at least a part of lithium from the composite oxide and a material capable of inserting and removing zinc ions. Become. That is, when the composite oxide is applied to a positive electrode of a zinc ion battery, it can exhibit a function as a positive electrode active material.

FIG. 2 is a schematic diagram for explaining a configuration of a zinc ion battery 100. FIG. 9 is a diagram showing evaluation results of Example 1. FIG. 9 is a diagram showing evaluation results of Example 2.

1. Positive electrode material for zinc ion batteries Spinel-type composite oxides containing lithium and manganese are known as positive electrode materials for lithium ion batteries. The present inventor has found that by removing a part of lithium from such a composite oxide, zinc ions can be inserted and removed at a predetermined potential. That is, the positive electrode material of the present disclosure is a positive electrode material used for a zinc ion battery, and has a spinel-type crystal phase including lithium, manganese, and oxygen.

1.1. Composition The composition of the positive electrode material of the present disclosure is not particularly limited as long as a spinel-type crystal phase containing lithium, manganese, and oxygen is maintained. In _particular, it is preferable to have a composition represented by _{Li x M y Mn 2-y} O 4 ± δ. Here, M is at least one selected from the group consisting of Ti, Ge, Fe, Co, Cr, Cu, Li, Al, Mg, Ga, Zn, Ni and V. The values of x and y in the above composition formula are not particularly limited as long as the spinel-type crystal phase can be maintained. For example, x is preferably 0.5 ≦ x ≦ 1.5, and more preferably 0.8 ≦ x ≦ 1.2. Y is preferably 0 ≦ y ≦ 1, more preferably 0 ≦ y ≦ 0.5. The value of δ is not particularly limited as long as a predetermined crystal phase is obtained. Specific examples of the composition that can easily constitute the spinel-type crystal phase include LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O ₄ .

1.2. Crystal Phase The cathode material of the present disclosure has a spinel-type crystal phase containing lithium, manganese, and oxygen. “Having a spinel crystal phase” means that at least a diffraction peak derived from the spinel crystal phase is confirmed in X-ray diffraction. Since the angle of the X-ray diffraction peak derived from the spinel-type crystal phase is obvious in this technical field, detailed description is omitted here.

  In the positive electrode material of the present disclosure, the spinel-type crystal phase includes lithium, manganese, and oxygen. Further, as illustrated in the composition formula above, in the spinel-type crystal phase, some elements may be replaced by different elements. That is, the spinel-type crystal phase may be composed of lithium, manganese, oxygen, and a different element other than these. In addition, the positive electrode material of the present disclosure may include other crystal phases in addition to the spinel-type crystal phase as long as the above problem can be solved. For example, when synthesizing a composite oxide containing lithium, manganese and cobalt, a layered rock salt type crystal phase may be generated together with a spinel type crystal phase, but the desired effect can be exhibited even in such a case.

1.3. Shape The shape and size of the positive electrode material of the present disclosure are not particularly limited, as long as they are applicable to the positive electrode of a zinc ion battery. It is preferably in the form of particles. When the positive electrode material is in the form of particles, the primary particle diameter is preferably 1 nm or more and 1000 μm or less. The lower limit is more preferably 5 nm or more, further preferably 10 nm or more, particularly preferably 50 nm or more, and the upper limit is more preferably 100 μm or less, further preferably 30 μm or less, and particularly preferably 10 μm or less. In the positive electrode material, the primary particles may be aggregated to form secondary particles. In this case, the particle size of the secondary particles is not particularly limited, but is usually 0.5 μm or more and 1000 μm or less. It is considered that when the particle diameter of the positive electrode material is in such a range, a positive electrode having more excellent ion conductivity and electron conductivity can be obtained.

1.4. Effects The positive electrode material of the present disclosure expresses a zinc ion deinsertion function by desorbing a part of lithium constituting the spinel-type crystal phase. Even if some lithium is desorbed from the positive electrode material of the present disclosure, the spinel crystal structure is considered to be maintained, and vacancies and the like generated by the desorption of lithium in the spinel crystal structure are considered. It is thought that zinc ions can be used to insert and remove zinc ions. When the positive electrode material of the present disclosure is applied to the positive electrode of a zinc ion battery, for example, when charging a zinc ion battery, lithium can be electrochemically desorbed from the positive electrode material to the negative electrode side, Since it is considered that the positive electrode material can exhibit the function of inserting and removing zinc ions, it is not always necessary to perform lithium desorption treatment from the positive electrode material in advance (for example, before manufacturing a battery). That is, the positive electrode material of the present disclosure may be directly applied to the positive electrode of a zinc ion battery without performing lithium desorption treatment, or may be subjected to lithium desorption processing in advance and then applied to the zinc ion battery. May be applied to the positive electrode. Details of the lithium desorption process will be described later.

2. Method for Producing Positive Electrode Material for Zinc Ion Battery The technology of the present disclosure also has an aspect as a method for producing a positive electrode material for a zinc ion battery. That is, the production method of the present disclosure is characterized in that a part of lithium constituting the spinel-type crystal phase is desorbed from a composite oxide having a spinel-type crystal phase containing lithium, manganese, and oxygen.

  The present inventor estimates that it is effective for the positive electrode material to maintain a spinel-type crystal structure even after lithium desorption treatment in order to exert a zinc ion deinsertion function. That is, it is preferable that not all of lithium is desorbed from the spinel-type crystal phase, but only part of lithium is desorbed. Various methods can be considered as a method for desorbing a part of lithium constituting the spinel-type crystal phase. For example, when lithium is electrochemically extracted from a spinel-type crystal phase, the amount of lithium extracted from the spinel-type crystal phase can be adjusted by adjusting a voltage or the like. Alternatively, when lithium is chemically removed from the spinel-type crystal phase by acid treatment, the amount of lithium extracted from the spinel-type crystal phase may be adjusted by adjusting the type of acid or the contact time with the acid. it can.

  As described above, the positive electrode material of the present disclosure may be applied to a positive electrode of a zinc ion battery after subjecting lithium to a desorption treatment in advance, or lithium may be produced from the positive electrode material after manufacturing the battery. It may be withdrawn electrochemically. That is, the timing of implementing the method for manufacturing a positive electrode material according to the present disclosure may be before or after manufacturing the battery.

3. Zinc ion battery The technology of the present disclosure also has an aspect as a zinc ion battery. FIG. 1 schematically shows the configuration of a zinc ion battery 100. As shown in FIG. 1, the zinc ion battery 100 includes a positive electrode 10, a negative electrode 20, and an electrolytic solution 30 which is in contact with the positive electrode 10 and the negative electrode 20 and contains zinc ions as carrier ions. Here, the zinc ion battery 100 has one feature in that the positive electrode 10 includes the above-described positive electrode material of the present disclosure. The zinc ion battery 100 of the present disclosure can also function as a secondary battery.

3.1. Positive electrode 10
The positive electrode 10 preferably includes a positive electrode current collector layer 10a and a positive electrode active material layer 10b in contact with the positive electrode current collector layer 10a. In this case, the positive electrode material of the present disclosure is included in the positive electrode active material layer 10b.

  As the positive electrode current collector layer 10a, a known metal that can be used as a positive electrode current collector layer of a zinc ion battery can be used. The type of metal constituting the positive electrode current collector layer is not particularly limited. For example, at least one selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Pb, Co, Cr, Ge, In, Sn, and Zr. The form of the positive electrode current collector layer 10a is not particularly limited. Various forms such as a foil shape, a mesh shape, and a porous shape can be adopted. The above metal may be deposited and plated on the surface of the substrate.

The positive electrode active material layer 10b includes the positive electrode material of the present disclosure. Specifically, the positive electrode active material layer 10b includes a positive electrode active material, and the positive electrode active material includes the positive electrode material of the present disclosure. The amount of the positive electrode active material contained in the positive electrode active material layer 10b is not particularly limited. For example, based on the entire positive electrode active material layer 10b (100% by mass), the positive electrode active material is preferably 20% by mass or more, more preferably 40% by mass or more, further preferably 60% by mass or more, and particularly preferably 70% by mass. It is included above. The upper limit is not particularly limited, but is preferably 99% by mass or less, more preferably 97% by mass or less, and further preferably 95% by mass or less. It is considered that when the content of the positive electrode active material is in such a range, the positive electrode 10 having more excellent ionic conductivity and electronic conductivity can be obtained. The positive electrode active material may be composed only of the positive electrode material of the present disclosure, or may include a known positive electrode active material in addition to the positive electrode material of the present disclosure. Known positive electrode active materials include α-MnO ₂ , Zn _0.25 V ₂ O ₅ and Prussian blue. In the positive electrode active material, the ratio occupied by the positive electrode material of the present disclosure is not particularly limited, and may be appropriately determined depending on the intended performance of the battery.

  The positive electrode active material layer 10b may contain a conductive auxiliary or a binder. As the conductive aid, any conductive aid used in zinc ion batteries can be employed. Specifically, a carbon material can be used. For example, a carbon material selected from Ketjen black (KB), vapor grown carbon fiber (VGCF), acetylene black (AB), carbon nanotube (CNT), carbon nanofiber (CNF), carbon black, coke, and graphite is preferable. . Alternatively, a metal material that can withstand the environment when the battery is used may be used. One kind of the conductive assistant may be used alone, or two or more kinds thereof may be used in combination. Various shapes such as a powder shape and a fiber shape can be adopted as the shape of the conductive auxiliary agent. The amount of the conductive additive contained in the positive electrode active material layer 10b is not particularly limited. For example, based on the entire positive electrode active material layer 10b (100% by mass), the conductive additive is preferably contained in an amount of 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more. I have. The upper limit is not particularly limited, but is preferably 50% by mass or less, more preferably 30% by mass or less, and further preferably 10% by mass or less. It is considered that when the content of the conductive additive is in such a range, the positive electrode 10 having more excellent ionic conductivity and electronic conductivity can be obtained. As the binder, any of the binders used in zinc ion batteries can be employed. For example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and the like. Only one binder may be used alone, or two or more binders may be used in combination. The amount of the binder contained in the positive electrode active material layer 10b is not particularly limited. For example, based on the entire positive electrode active material layer 10b (100% by mass), the binder is preferably contained in an amount of 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more. The upper limit is not particularly limited, but is preferably 50% by mass or less, more preferably 30% by mass or less, and further preferably 10% by mass or less. When the content of the binder is in such a range, the positive electrode material and the like of the present disclosure can be appropriately bound, and the positive electrode 10 having more excellent ionic conductivity and electronic conductivity can be obtained. Can be

  The thickness of the positive electrode active material layer 10b is not particularly limited, but is preferably, for example, 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

3.2. Negative electrode 20
As the negative electrode 20, any known negative electrode for a zinc ion battery can be adopted. In particular, the negative electrode 20 preferably includes a negative electrode current collector layer 20a and a negative electrode active material layer 20b that is in contact with the negative electrode current collector layer 20a.

  The negative electrode current collector layer 20a can be made of a known metal that can be used as a negative electrode current collector layer of a zinc ion battery. As such a metal, at least one selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Pb, Co, Cr, Zn, Ge, In, Sn, and Zr. A metal material containing an element can be exemplified. In particular, the negative electrode current collector layer 20a is preferably made of Cu plated with Cu, Ni, Zn, Sn, Sn, or Ni plated with Sn or Zn plated with Sn. Alternatively, a Zn foil may be used as both the negative electrode current collector layer 20a and the negative electrode active material layer 20b. The form of the negative electrode current collector layer 20a is not particularly limited. Various forms such as a foil shape, a mesh shape, and a porous shape can be adopted. The above-mentioned metal may be plated and deposited on the surface of a substrate other than the metal.

  The negative electrode active material layer 20b contains a negative electrode active material. Further, the negative electrode active material layer 20b may contain a conductive auxiliary or a binder in addition to the negative electrode active material. As the negative electrode active material, any known negative electrode active material for a zinc ion battery can be adopted. For example, metallic zinc and zinc oxide. As the negative electrode active material, only one kind may be used alone, or two or more kinds may be used in combination. The shape of the negative electrode active material is not particularly limited. For example, the negative electrode active material may be plated on the surface of the negative electrode current collector layer 20a to form a thin film. Alternatively, a metal foil shape such as a Zn foil may be used. Alternatively, it may be in the form of particles. When the negative electrode active material is in the form of particles, the amount of the negative electrode active material contained in the negative electrode active material layer 20b is not particularly limited. For example, based on the entire negative electrode active material layer 20b (100% by mass), the negative electrode active material is preferably 20% by mass or more, more preferably 40% by mass or more, further preferably 60% by mass or more, and particularly preferably 70% by mass. It is included above. The upper limit is not particularly limited, and is adjusted according to the presence or absence and amount of the conductive auxiliary agent and the binder. As described above, when the negative electrode active material is plated on the surface of the negative electrode current collector layer 20a or when the negative electrode active material layer 20a is formed of a metal foil, the conductive auxiliary agent and the binder are unnecessary. The thickness of the negative electrode active material layer 20a is not particularly limited, but is, for example, preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

3.3. Electrolyte 30
In an electrolytic solution-based zinc ion battery, an electrolytic solution exists inside the positive electrode, inside the negative electrode, and between the positive electrode and the negative electrode, whereby the zinc ion conductivity between the positive electrode and the negative electrode is reduced. Secured. This form is also adopted in the battery 100. Specifically, in the battery 100, a separator (not shown) is provided between the positive electrode 10 and the negative electrode 20, and the separator, the positive electrode active material layer 10b, and the negative electrode active material layer 20b are both electrolytic solutions. 30. The electrolytic solution 30 has penetrated into the inside of the positive electrode active material layer 10b and the negative electrode active material layer 20b. The electrolytic solution 30 may be any electrolytic solution containing zinc ions as carrier ions, and may be an aqueous electrolytic solution or a non-aqueous electrolytic solution. Particularly, an aqueous electrolyte is preferable. That is, the electrolytic solution 30 preferably contains water as a main component of the solvent. In this case, water accounts for 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more, based on the total amount of the solvent constituting the electrolyte 30 (100 mol%). On the other hand, the upper limit of the proportion of water in the solvent is not particularly limited. The solvent may consist only of water. On the other hand, even when the electrolytic solution 30 is an aqueous electrolytic solution, a solvent other than water may be contained in addition to water, for example, from the viewpoint of forming SEI (Solid Electrolyte Interphase) on the surface of the electrode. Examples of the solvent other than water include one or more organic solvents selected from ethers, carbonates, nitriles, alcohols, ketones, amines, amides, sulfur compounds, and hydrocarbons. When the electrolytic solution 30 is an aqueous electrolytic solution, the solvent other than water is preferably 50 mol% or less, more preferably 30 mol% or less, and still more preferably 10 mol%, based on the total amount of the solvent constituting the electrolyte solution (100 mol%). %, Particularly preferably 5 mol% or less. The electrolyte is dissolved in the electrolyte solution 30, and the electrolyte can be dissolved in the electrolyte solution and dissociated into cations and anions. Examples of the electrolyte include various zinc salts. For example, Zn (CF ₃ SO ₃ ) ₂ or zinc sulfate is used. The concentration of the electrolyte in the electrolyte solution 30 is not particularly limited, and may be appropriately determined according to the intended performance of the battery. The electrolytic solution 30 may contain an acid, a hydroxide, or the like for adjusting the pH of the electrolytic solution, in addition to the above-mentioned solvent and electrolyte. Further, various additives may be included.

3.4. Other Configurations As described above, in the zinc ion battery 100, it is preferable to provide a separator between the positive electrode 10 and the negative electrode 20. It is preferable to use a separator used in a conventional electrolyte battery (a lithium ion battery, a nickel hydride battery, a zinc air battery, etc.). When an aqueous electrolyte is used as the electrolyte 30, a hydrophilic separator such as a nonwoven fabric made of cellulose can be preferably used as the separator. The thickness of the separator is not particularly limited. For example, a separator having a thickness of 5 μm or more and 1 mm or less can be used.

  The zinc ion battery 100 may include a terminal, a battery case, and the like in addition to the above configuration. The other configuration is self-evident, and the description is omitted here.

4. Method for Manufacturing Zinc Ion Battery The zinc ion battery 100 includes, for example, a step of manufacturing the positive electrode 10, a step of manufacturing the negative electrode 20, a step of manufacturing the electrolyte 30, and the manufactured positive electrode 10, the negative electrode 20, and the electrolyte 30. In a battery case.

4.1. Manufacture of Positive Electrode The process of manufacturing the positive electrode may be the same as a known process except that the above-described positive electrode material of the present disclosure is used as the positive electrode material. For example, a positive electrode mixture paste (slurry) is obtained by dispersing a positive electrode material or the like constituting the positive electrode active material layer 10b in a solvent. The solvent used in this case is not particularly limited, and water and various organic solvents can be used. The positive electrode mixture paste (slurry) is applied to the surface of the positive electrode current collector layer 10a using a doctor blade or the like, and then dried to form the positive electrode active material layer 10b on the surface of the positive electrode current collector layer 10a. And the positive electrode 10. As a coating method, in addition to the doctor blade method, an electrostatic coating method, a dip coating method, a spray coating method, or the like can be adopted. Alternatively, a powder containing a positive electrode material may be formed in a dry manner, and may be superimposed on a positive electrode current collector layer to form a positive electrode. As described above, the lithium elimination process from the positive electrode material of the present disclosure may be performed before manufacturing the positive electrode 10, or the lithium elimination process from the positive electrode material of the present disclosure may be performed after manufacturing the positive electrode 10. You may.

4.2. Production of Negative Electrode The process for producing the negative electrode may be the same as a known process. For example, as described above, the negative electrode 20 can be obtained by plating the surface of the negative electrode current collector layer 20a with a negative electrode active material (for example, metal zinc). Alternatively, a metal foil such as a Zn foil may be used as it is as the negative electrode. Alternatively, the negative electrode active material and the like constituting the negative electrode active material layer 20b are dispersed in a solvent to obtain a negative electrode mixture paste (slurry). The solvent used in this case is not particularly limited, and water and various organic solvents can be used. The negative electrode mixture paste (slurry) is applied to the surface of the negative electrode current collector layer 20a using a doctor blade or the like, and then dried to form the negative electrode active material layer 20b on the surface of the negative electrode current collector layer 20a. And the negative electrode 20. As a coating method, in addition to the doctor blade method, an electrostatic coating method, a dip coating method, a spray coating method, or the like can be adopted. Alternatively, a powder containing the negative electrode active material may be formed in a dry process, and may be laminated with the negative electrode current collector layer to form a negative electrode.

4.3. Manufacture of Electrolyte Solution The electrolyte solution 30 can be manufactured by adding a predetermined electrolyte, an optional additive and the like to a predetermined solvent and mixing them.

4.4. Housing in Battery Case The manufactured positive electrode 10, negative electrode 20 and electrolytic solution 30 are housed in a battery case to form a zinc ion battery 100. For example, a separator is sandwiched between the positive electrode 10 and the negative electrode 20 to obtain a laminate having the positive electrode current collector layer 10a, the positive electrode active material layer 10b, the separator, the negative electrode active material layer 20b, and the negative electrode current collector layer 20a in this order. Other members such as terminals are attached to the laminate as needed. The stacked body is accommodated in the battery case, the battery case is filled with the electrolyte solution 30, and the stacked body is immersed in the electrolyte solution 30 to seal the stacked body and the electrolyte solution in the battery case. The battery 100 can be used.

5. Supplement In addition to α-MnO ₂ disclosed in Non-Patent Document 1, Prussian blue and Zn _0.25 V ₂ O ₅ are known as positive electrode materials for zinc ion batteries. When α-MnO ₂ is used, there is a problem of deterioration due to a conversion reaction and a problem that H ₂ O is involved in the reaction. Prussian blue has problems in terms of capacity and life. Zn _0.25 V ₂ O ₅ has a problem that the operating potential is low due to the relation of the oxidation-reduction potential of V. The positive electrode material of the present disclosure can be expected as a new material that has a possibility of solving such a problem.

1. Example 1
1.1. Preparation of Electrolytic Solution Zn (CF ₃ SO ₃ ) _2- was dissolved in water to obtain an electrolytic solution. The concentration of Zn (CF ₃ SO ₃ ) _2- was 5 mol per 1 kg of water. The prepared electrolytic solution is subjected to temperature control at 30 ° C. overnight in a constant temperature bath, and is used after the temperature is stabilized in a 25 ° C. constant temperature bath at least 3 hours before the following evaluation. did.

1.2. Preparation of Positive Electrode (Working Electrode) Each was weighed and mixed with NMP so that the mass ratio of the positive electrode material: the conductive auxiliary agent: the binder was 85: 10: 5 to obtain a positive electrode mixture slurry. Here, spinel-type lithium manganate (LiMn ₂ O ₄ ) was used as a positive electrode material, acetylene black was used as a conductive additive, and PVdF was used as a binder. Specifically, after mixing the positive electrode material and the conductive assistant in a mortar, a binder was added and further mixed, NMP was added while confirming the viscosity, and the mixing in the mortar was continued. Thereafter, the mixture was transferred to an ointment container and mixed with Awatori Nerita (Shinky) at 3000 rpm for 10 minutes to obtain a positive electrode mixture slurry. The obtained slurry was placed on the surface of a Ti foil (manufactured by Nilaco Co., Ltd.), and was coated with a doctor blade so as to have a predetermined basis weight. Thereafter, the resultant was dried overnight in a dryer at 60 ° C. to prepare a positive electrode (working electrode) for evaluation. The obtained positive electrode was punched out at φ16 mm and roll-pressed so that the porosity was about 40%. In the positive electrode finally obtained, the basis weight of the mixture was about 0.6 mAh / cm ² .

1.3. Preparation of Evaluation Cell The prepared positive electrode (working electrode) and a Zn foil (manufactured by Nilaco) as a counter electrode were assembled to a facing cell (SB1A, manufactured by EC Frontier) having an opening diameter of 13 mm. An evaluation cell was prepared by using Ag / AgCl (manufactured by Interchem) as a reference electrode and injecting an electrolyte (about 2 cc) into the cell.

1.4. Evaluation conditions A sweep was started from the OCP to the anode side under the following apparatus and conditions, and 1.3 V vs. 1.3 V was applied. The sweep was reversed with Ag / AgCl. By repeating this for 10 cycles, part of lithium was extracted from the positive electrode material (LiMn ₂ O ₄ ) in the positive electrode (the lithium desorption process was completed). Then, from OCP to -0.6 V vs.. After the cathode sweep was performed to Ag / AgCl, the sweep was reversed, and 1.3 V vs. 1.3 V was again applied to the anode side. By sweeping to Ag / AgCl, it was evaluated whether zinc ions could be inserted and removed from the positive electrode material.

[Apparatus] Electrochemical measurement apparatus: VMP3 (Bio Logic)
Constant temperature bath: LU-124 (manufactured by Espec)
[Conditions] Cyclic voltammetry (CV), 1 mV / s, 25 ° C

FIG. 2A shows the CV of spinel-type LiMn ₂ O ₄ in the lithium desorption treatment (first and tenth cycles). As shown in FIG. 2A, an oxidation peak can be confirmed at around 1.2 V in the first cycle of the lithium desorption treatment. This is due to the elimination of lithium from LiMn ₂ O ₄ . In the first cycle of the lithium desorption treatment, a reduction peak can be confirmed at around 1.0 V. This is because, among the lithium desorbed from LiMn ₂ O ₄ , lithium existing at the interface between the electrolyte and the positive electrode was inserted again into LiMn ₂ O ₄ . Thereafter, the lithium desorption treatment proceeded, and in the tenth cycle, the oxidation-reduction peak could not be confirmed. That is, it can be said that almost all of the lithium that can be desorbed in the above potential range has been desorbed from LiMn ₂ O ₄ . Lithium desorbed from LiMn ₂ O ₄ is considered to have diffused into the electrolytic solution. In the above potential range, it is considered that only a part of lithium constituting spinel type LiMn ₂ O ₄ is eliminated, and the cathode material maintains the spinel type crystal structure.

FIG. 2B shows the CV (-0.6 to 1.3 V vs. Ag / AgCl) in the first cycle after the completion of the lithium desorption treatment (after the tenth cycle). As shown in FIG. 2 (B), a reduction peak can be confirmed around -0.087V. This is due to the insertion of zinc ions into the positive electrode material after lithium removal. Further, an oxidation peak can be confirmed at around 0.91 V. This is due to the desorption of zinc ions inserted into the positive electrode material. As described above, it was found that spinel-type LiMn ₂ O ₄ allows zinc ions to be inserted and removed after a part of lithium is eliminated, and can function as a positive electrode active material of a zinc ion battery. For example, the positive electrode material according to Example 1 has a zinc ion desorption potential of 0.5 V vs. average. Ag / AgCl (average of the reduction peak potential (-0.08 V) and the oxidation peak potential (0.91 V)), the metal zinc (the zinc ion deinsertion potential is about -0.8 to- 0.9V vs. Ag / AgCl), it is considered that a zinc ion battery having a voltage of about 1.3 to 1.4 V can be manufactured.

2. Example 2
LiNi _0.5 Mn _1.5 O ₄ was used in place of LiMn ₂ O ₄ as the positive electrode material, and the sweep potential on the anode side was _1.5 Vvs. Except for using Ag / AgCl, an evaluation cell was prepared and evaluated in the same manner as in Example 1.

FIG. 3 shows the CV (-0.6 to 1.5 V vs. Ag / AgCl) in the first cycle after the completion of the lithium desorption treatment (after the tenth cycle). As shown in FIG. 3, a reduction peak can be confirmed around -0.25V. This is due to the insertion of zinc ions into the positive electrode material after lithium removal. Further, an oxidation peak can be confirmed at around 0.9 V. This is due to the desorption of zinc ions inserted into the positive electrode material. As described above, even when some elements are replaced with different elements in spinel-type lithium manganate, such as LiNi _0.5 Mn _1.5 O ₄ , it can be applied as a positive electrode material for a zinc ion battery. It turned out to be.

  From the results of Examples 1 and 2, some elements in the spinel-type lithium manganate were replaced with different elements (eg, Ni, Ti, Ge, Fe, Co, Cr, Cu, Li, Al , Mg, Ga, Zn, V, etc.) as long as the spinel-type crystal phase can be maintained, it is considered that the same performance can be exhibited as a positive electrode material of a zinc ion battery. The spinel structure is easily maintained in the composite oxide containing manganese together with lithium. That is, it is considered that a desired function as a positive electrode material of a zinc ion battery can be exhibited if a spinel-type crystal phase including lithium, manganese, and oxygen is provided.

  A zinc ion battery using the positive electrode material of the present disclosure can be widely used from a large power supply for a vehicle to a small power supply for a portable terminal.

Reference Signs List 10 positive electrode 10a positive electrode current collector layer 10b positive electrode active material layer 20 negative electrode 20a negative electrode current collector layer 20b negative electrode active material layer 30 electrolytic solution 100 zinc ion battery

Claims (1)

Having a spinel-type crystal phase containing lithium, manganese, and oxygen,
Positive electrode material for zinc ion batteries.