KR102069739B1 - Electrode Active Material and Secondary Battery Having the Same - Google Patents

Abstract

It provides an electrode active material and a secondary battery comprising the same. The electrode active material is vanadium oxyhydrate having a tunnel formed by arranging (V _1-x M _x ) O ₆ octahedrons in a crystal structure in a 2 × 2 manner. In this case, x may be 0 to 0.1, and M may be a metal having an oxidation number of +3 or +4.

Description

Electrode active material and secondary battery comprising same {Electrode Active Material and Secondary Battery Having the Same}

The present invention relates to a secondary battery, and more particularly, to a secondary battery including an active material having a new structure.

The secondary battery refers to a battery that can be repeatedly used because it can be charged as well as discharged. The representative lithium secondary battery of the secondary battery is lithium ions contained in the positive electrode active material is transferred to the negative electrode through the electrolyte and then inserted into the layered structure of the negative electrode active material (charging), after which the lithium ion inserted into the layered structure of the negative electrode active material is again It works on the principle of returning to the anode (discharge). Such lithium secondary batteries are currently commercialized and used as small power sources for mobile phones, notebook computers, and the like, and are expected to be used as large power sources for hybrid cars, and thus, demand for them is expected to increase.

However, a composite metal oxide mainly used as a positive electrode active material in a lithium secondary battery contains rare metal elements such as lithium, and thus may not meet demand growth. Accordingly, research is being conducted on sodium secondary batteries using abundant and cheap sodium as a cathode active material. As an example, Korean Patent Laid-Open Publication No. 2012-0133300 discloses A _x MnPO ₄ F (A = Li or Na, 0 <x ≦ 2) as a cathode active material.

The cathode active material reacts sensitively with moisture in the air, so that side reactions occur, and as a result, problems such as capacity loss and lifespan of the battery may be caused.

Accordingly, the problem to be solved by the present invention is to provide an active material for a secondary battery and a secondary battery comprising the same, which improves stability by reducing reactivity with water in the air.

One aspect of the present invention to achieve the above object provides an electrode active material. The electrode active material is vanadium oxyhydrate having a tunnel formed by arranging (V _{1- x} M _x ) O ₆ octahedrons in a crystal structure in a 2 × 2 manner. X is 0 to 0.1 and M is a metal having an oxidation number of +3 or +4. As one example, M may be Al, Si, Cr, or Fe.

Oxygen ions may be disposed in the tunnel. The tunnel may contain lithium ions, sodium ions, or zinc ions.

The electrode active material according to another example may be vanadium oxyhydrate represented by the following Chemical Formula 1.

[Formula 1]

(V _1-x M _x ) O _1.52 (OH) _0.77

In Formula 1, x is 0 to 0.1, M is a metal having an oxidation number of +3 or +4. As one example, M may be Al, Si, Cr, or Fe.

The vanadium oxyhydrate may have a hollandite crystal structure. Furthermore, the vanadium oxyhydrate may have a space group of I 4 / m.

Another aspect of the present invention to achieve the above object provides a secondary battery. The secondary battery may include a positive electrode including the electrode active material, a negative electrode containing a negative electrode active material into which metal ions may be inserted, and an electrolyte disposed between the positive electrode and the negative electrode. The metal ions may be lithium ions, sodium ions, or zinc ions.

According to the present invention, the vanadium oxyhydrate has a form of a hydrate and does not form a by-product by reaction with moisture in the air, thereby improving stability of the secondary battery.

In addition, the vanadium oxyhydrate has a 2 × 2 tunnel structure in the crystal structure, and can be used as an active material of a secondary battery by inserting or detaching metal ions.

1A and 1B are schematic views showing the crystal structure of vanadium oxyhydrate according to an embodiment of the present invention.
2 is a schematic view showing a crystal structure of vanadium oxyhydrate according to another embodiment of the present invention.
3 is a flowchart illustrating a method of manufacturing an active material according to an embodiment of the present invention.
4 is a graph showing the results of XRD analysis on the powder obtained in Preparation Example 1-1.
5 is a graph showing the results of XRD analysis for the powder obtained in Preparation Examples 1-2 and 1-3.
6 is a SEM photograph of the powder obtained in Preparation Example 1-1.
7 and 8 are SEM pictures of the powder obtained in Preparation Example 1-2 and Preparation Example 1-3, respectively.
9 shows TEM pictures of the powders obtained in Preparation Examples 1-1, 1-2, and 1-3.
10 is a schematic diagram showing ion diffusion distances of VO _1.52 (OH) _0.77 particles (Preparation Example 1-1) and vanadium oxyhydrate particles (Preparation Examples 1-2, 1-3) doped with Al ions.
FIG. 11 is a graph showing the BET (Brunauer-Emmett-Teller) surface area of Al doping degree of powders obtained in Preparation Examples 1-1, 1-2, and 1-3.
12A and 12B are graphs showing charge and discharge characteristics of a first cycle of a lithium ion half cell obtained through Preparation Example 3 using VO _1.52 (OH) _0.77 positive electrode active material of Preparation Example 1-1, respectively, and showing cycle characteristics. It is a graph.
13 is of Preparation _{1-2 (V 0. 95 Al 0.} 05) O 1 .52 (OH) 0.77 charge and discharge characteristics of the lithium ion inversion fingers first cycle obtained from the Preparation Example 3 using the positive electrode active material 14 is a graph showing charge and discharge characteristics of a first cycle of a lithium ion half cell obtained through Preparation Example 3 using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3. The graph shown.
15A and 15B are graphs showing charge and discharge characteristics of a first cycle of a sodium ion half cell obtained through Preparation Example 4 using VO _1.52 (OH) _0.77 positive electrode active material of Preparation Example 1-1, respectively, and showing cycle characteristics. It is a graph.
16 is prepared in Example 1-2 _{(V 0. 95 Al 0. 05} ) O 1 .52 (OH) 0.77 charge and discharge characteristics of the sodium ion reversal fingers first cycle obtained from the Production Example 4 by using the positive electrode active material 17 is a graph showing charge and discharge characteristics of a first cycle of a sodium ion _half cell obtained through Preparation Example 4 using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3. The graph shown.
18A and 18B are graphs showing charge and discharge characteristics of a first cycle of a zinc ion half cell obtained through Preparation Example 5 using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1, respectively, and showing cycle characteristics. It is a graph.
19 is prepared in Example 1-2 _{(V 0. 95 Al 0. 05} ) O 1 .52 (OH) 0.77 charge and discharge characteristics of the zinc ion inversion fingers first cycle obtained from the Production Example 5 by using the positive electrode active material 20 is a graph showing charge and discharge characteristics of a first cycle of a zinc ion half cell obtained in Preparation Example 5 using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3. The graph shown.
FIG. 21 is a bond valence sum (BVS) energy map at bc plane of VO _1.52 (OH) _0.77 crystal. FIG. This is the result calculated through density functional theory (DFT) calculation.
FIG. 22A illustrates an in-situ XRD graph of cathode active materials during an initial cycle of a lithium ion half cell obtained through Preparation Example 3 using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1, and FIG. 22B is Preparation Example 1 In situ XRD graphs of the positive electrode active materials in the initial cycle of the sodium ion _half cell obtained in Preparation Example 4 using VO _1.52 (OH) _0.77 positive electrode active material of -1.
FIG. 22C illustrates an X-situ XRD graph of positive electrode active materials during an initial cycle of a zinc ion half cell obtained through Preparation Example 5 using VO _1.52 (OH) _0.77 positive electrode active material of Preparation Example 1-1.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to describe the present invention in more detail. However, the invention is not limited to the embodiments described herein but may be embodied in other forms. Like numbers refer to like elements throughout the specification.

Active material for secondary battery

The active material according to an embodiment of the present invention may be vanadium oxyhydroxide having a tunnel structure formed by arranging (V _{1- x} M _x ) O ₆ octahedrons in a 2 × 2 crystal structure. In this case, x may be 0 to 0.1, and M is a metal having an oxidation number of +3 or +4, specifically, a transition metal having a oxidation number of +3 or +4, a post-transition metal Or metalloid. As one example, M may be Al, Si, Cr, or Fe.

Such vanadium oxyhydrate can be represented by the following formula (1).

[Formula 1]

(V _1-x M _x ) O _1.52 (OH) _0.77

In Chemical Formula 1, x may be 0 to 0.1, and M may be a metal having an oxidation number of +3 or +4, specifically, a transition metal, a post-transition metal, or a metalloid having an oxidation number of +3 or +4. As one example, M may be Al, Si, Cr, or Fe. At this time, the oxidation number of V may be +3.2 to +4.

1A and 1B are schematic views showing the crystal structure of vanadium oxyhydrate according to an embodiment of the present invention. Specifically, in Formula 1, x is a schematic diagram showing vanadium oxyhydrate which is 0.

1A and 1B, the vanadium oxyhydrate may have a tunnel structure in which VO ₆ octahedrons are arranged in a 2 × 2 array in a crystal structure. This vanadium oxyhydrate may have a crystal structure such as hollandite, and the space group is I4 / m.

Specifically, a pair of VO ₆ octahedrons form a double chain while sharing one side, and four double chains (four pairs of VO ₆ octahedrons) are arranged while rotating about 90 degrees while sharing vertices. X2 tunnels can be formed. Oxygen anions may be disposed in this tunnel. The diameter of this tunnel may be about 5.477 kPa.

Since the tunnel in the vanadium oxyhydrate crystal structure has a size sufficient to accommodate metal ions, specifically, metal cations (A ^{n +} ), the metal ions may be inserted into or inserted into the tunnel. In addition, the oxygen anion disposed in the tunnel can reduce the mutual repulsion force between the cations when the metal cations are inserted, thereby maintaining the tunnel structure more securely during battery operation. In this instance, the metal cation may be a monovalent or divalent ^{Li +, Na +, K +} , Zn ^{2 +,} or a cation, and one example. Therefore, the vanadium oxyhydrate crystal is an example of a metal secondary battery, and may be applied as an active material to various secondary batteries such as sodium secondary batteries, potassium secondary batteries, and zinc secondary batteries as well as lithium ion secondary batteries. .

2 is a schematic view showing a crystal structure of vanadium oxyhydrate according to another embodiment of the present invention. Specifically, in Formula 1, x is a schematic diagram showing vanadium oxyhydrate greater than zero.

Referring to FIG. 2, the structure is the same as that of FIGS. 1A and 1B, but a part of V is substituted with M. In other words, vanadium oxyhydrate doped with M. In this case, M may be a metal having an oxidation number of +3 or +4. As one example, M may be Al, Si, Cr, or Fe.

3 is a flowchart illustrating a method of manufacturing an active material according to an embodiment of the present invention.

Referring to FIG. 3, a mixed solution containing vanadium oxy halide and a solvent may be prepared (S10). The vanadium oxy halide is a substance in which vanadium has an oxidation number of +5, and may be represented by VOX ₃ (where X is F, Cl, Br, or I). The solvent may be, for example, benzyl alcohol as an alcohol. The mixed solution can be stirred.

The mixed solution may be put in a sealed reactor and the mixed solution may be reacted at a boiling point or more of the mixed solution (S20). This reaction may be called solvent thermal synthesis. In this reaction vanadium oxyhydrate crystals can be produced as a result of the reaction.

The reaction product may be filtered, washed, and dried to obtain vanadium oxyhydrate powder. At this time, washing may be performed using alcohol, and drying may be performed by heat treatment in an oven in an air atmosphere.

In another embodiment, as an example, an aluminum salt may be added to the doping metal salt, that is, a salt of the metal represented by M in Chemical Formula 1 in the process of preparing the mixed solution.

Metal secondary battery

A metal secondary battery according to an embodiment of the present invention may include a positive electrode containing the active material described above as a positive electrode active material, a negative electrode containing a negative electrode active material into which metal ions can be inserted, and an electrolyte positioned therebetween. . In this case, the metal may be lithium, sodium, potassium, or zinc.

<Positive>

The cathode material may be obtained by mixing the cathode active material, the conductive material, and the binder. In this case, the conductive material may be a carbon material such as natural graphite, artificial graphite, cokes, carbon black, carbon nanotubes, graphene, or the like. The binder may be a thermoplastic resin such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoride, vinylidene fluoride copolymer, fluorine resin such as hexafluoropropylene, and / or polyolefin resin such as polyethylene or polypropylene. It may include.

The positive electrode material may be applied onto the positive electrode current collector to form a positive electrode. The positive electrode current collector may be a conductor such as Al, Ni, stainless or the like. The application of the positive electrode material onto the positive electrode current collector may be made by pressure molding or by forming an paste using an organic solvent or the like, and then applying the paste onto the current collector and pressing to fix the paste. The organic solvent is amine type, such as N, N- dimethylaminopropylamine and diethyltriamine; Ethers such as ethylene oxide and tetrahydrofuran; Ketones such as methyl ethyl ketone; Esters such as methyl acetate; Aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Application of the paste onto the positive electrode current collector can be performed using, for example, a gravure coating method, a slit die coating method, a knife coating method, a spray coating method.

<Cathode>

Cathode active materials include metals, metal alloys, metal oxides, metal fluorides, metal sulfides, and natural graphite, artificial graphite, coke, carbon black, carbon nanotubes, and graphene, which can deintercalate metal ions or cause conversion reactions. It can also form using carbon materials, such as a fin.

The negative electrode material can be obtained by mixing the negative electrode active material, the conductive material, and the binder. In this case, the conductive material may be a carbon material such as natural graphite, artificial graphite, cokes, carbon black, carbon nanotubes, graphene, or the like. The binder may be a thermoplastic resin such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene tetrafluoride, vinylidene fluoride copolymer, fluorine resin such as hexafluoropropylene, and / or polyolefin resin such as polyethylene or polypropylene. It may include.

The negative electrode material may be applied onto the positive electrode current collector to form a positive electrode. The positive electrode current collector may be a conductor such as Al, Ni, stainless or the like. The application of the negative electrode material on the positive electrode current collector may be made by pressure molding or a method of making a paste using an organic solvent or the like, and then applying the paste onto the current collector and pressing to fix the paste. The organic solvent is amine type, such as N, N- dimethylaminopropylamine and diethyltriamine; Ethers such as ethylene oxide and tetrahydrofuran; Ketones such as methyl ethyl ketone; Esters such as methyl acetate; Aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Application of the paste onto the negative electrode current collector can be performed using, for example, a gravure coating method, a slit die coating method, a knife coating method, a spray coating method.

<Electrolyte>

The electrolyte may be a liquid electrolyte containing a metal salt and a solvent for dissolving it. Specifically, in the case of sodium secondary batteries, sodium salts are NaClO ₄ , NaPF ₆ , NaAsF ₆ , NaSbF ₆ , NaBF ₄ , NaCF ₃ SO ₃ , NaN (SO ₂ CF ₃ ) ₂ , NaAlCl ₄ , Lower aliphatic carboxylate Salt or the like, or a mixture of two or more thereof. For lithium secondary batteries, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiN (SO ₂ CF ₃ ) ₂ , chloroborane lithium salt, lower aliphatic carboxylic acid lithium salt, tetraphenyl phenyl borate salt, and the like, or a mixture of two or more thereof may be used. In the case of a zinc secondary battery, the zinc salt may be ZnSO ₄ , Zn (NO ₃ ) _{2 ,} ZnCl ₂ , or the like, or a mixture of two or more thereof may be used.

The solvent may be an organic solvent. Examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and isopropyl methyl carbonate. Carbonates such as vinylene carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one and 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethylether, 2,2,3,3-tetrafluoropropyldifluoromethylether, tetrahydrofuran, 2-methyltetrahydro Ethers such as furan; Esters such as methyl formate, methyl acetate and γ-butyrolactone; Nitriles such as acetonitrile and butyronitrile; Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propanesultone; Or what introduce | transduced the fluorine substituent further to the said organic solvent can be used.

However, the electrolyte is not limited thereto, and may be a polymer solid electrolyte or a ceramic solid electrolyte in which the liquid electrolyte is impregnated in a polymer. In the polymer type solid electrolyte, the polymer may be a polymer compound including at least one or more of a polyethylene oxide polymer compound, a polyorganosiloxane chain, or a polyoxyalkylene chain. The ceramic solid electrolyte may use inorganic ceramics such as sulfides, oxides, and phosphates of the metal. A solid electrolyte may play the role of the separator mentioned later, and a separator may not be needed in that case.

<Separator>

The separator may be disposed between the positive electrode and the negative electrode. Such a separator may be a material having a form such as a porous film made of a material such as polyolefin resin such as polyethylene or polypropylene, a fluorine resin, a nitrogen-containing aromatic polymer, a nonwoven fabric, a woven fabric, or the like. The thickness of the separator is preferably as thin as long as the mechanical strength is maintained in that the volume energy density of the battery becomes high and the internal resistance becomes small.

<Method for Manufacturing Metal Secondary Battery>

A positive electrode, a separator, and a negative electrode are laminated in order to form an electrode group, and if necessary, the electrode group can be rolled up and stored in a battery can, and a sodium secondary battery can be produced by impregnating the electrode group with an electrolyte solution. Alternatively, a metal secondary battery may be manufactured by stacking a positive electrode, a solid electrolyte, and a negative electrode to form an electrode group, and then rolling the electrode group in a battery can if necessary.

Hereinafter, preferred examples are provided to aid the understanding of the present invention. However, the following experimental example is only for helping understanding of the present invention, and the present invention is not limited by the following experimental example.

[Experimental Examples; Examples]

Production Example  1: Preparation of vanadium oxyhydrate

Production Example  1-1: VO _1.52 (OH) _0.77  Produce

VOCL ₃ (0.913 g) and benzyl alcohol (20 ml) were mixed and stirred until the color of the mixture changed from yellow to green to blue. The stirred mixture was then placed in an autoclave and heat treated at 150 ° C. for 24 hours. After synthesis, the produced material was filtered and washed three times with ethanol, and then air dried in an oven at 80 ° C. for 24 hours to obtain a powder.

Production Example  1-2: (V _{0. 95} Al _{0 . 05} ) O _{One .52} (OH) _0.77  Produce

Instead of mixing the VOCL ₃ (0.913g) and benzyl alcohol _{(20ml), VOCL 3 (0.867g} ), AlCl 3 (0.035g), and benzyl as in the Production Example 1-1, except that the mixture of alcohol (20ml) The powder was obtained using the same method.

Production Example  1-3: (V _{0. 91} Al _{0 . 09} ) O _{One .52} (OH) _0.77  Produce

Instead of mixing the VOCL ₃ (0.913g) and benzyl alcohol _{(20ml), VOCL 3 (0.821g} ), AlCl 3 (0.0705g), and benzyl as in the Production Example 1-1, except that the mixture of alcohol (20ml) The powder was obtained using the same method.

4 is a graph showing the results of XRD analysis on the powder obtained in Preparation Example 1-1.

Referring to FIG. 4, the main peak has 2θ at positions 11.9 °, 16.9 °, and 27 °, which are the peaks for (3 1 0), (1 1 0), and (0 2 0), respectively. In addition, the half width of each peak is 0.305, 0.254, and 0.295, respectively.

From this powder, the results obtained in Production Example it can be seen that while gateu a single phase crystal of the Hall randayi agent (hollandite) structure with a space group of _{I4 / m VO 1.52 (OH)} 0. 77.

5 is a graph showing the results of XRD analysis for the powder obtained in Preparation Examples 1-2 and 1-3.

Referring to FIG. 5, it can be seen that peaks appear at almost the same position as the XRD analysis result of FIG. 4. The results of the powder while gateu also single-phase crystals obtained in Production Examples 1-3 to 1-2, and from, the hole having a space group of I4 / m randayi agent (hollandite) structure _{(V 0. 95 Al 0. 05} ) O _{1 .52} (OH) _{0. 77} and _{(V 0. 91 Al 0. 09} ) it can be seen that the _{O 1 .52 (OH) 0. 77} .

However, the peaks shifted slightly in the direction in which 2θ increases, which was determined to be because the particles of the powder become somewhat smaller, as can also be seen in the SEM photographs described later.

Table 1 below shows the lattice parameters of each structure obtained from the information of FIGS. 4 and 5.

Grid parameters a-axis c-axis Volume (Å ³ ) VO _1.52 (OH) _0.77 10.4018 2.9969 323.473 (V _0.95 Al _0.05 ) O _1.52 (OH) _0.77 10.3351 2.9472 314.985 (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 10.3132 2.9293 311.581

Referring to Table 1, it can be seen that the lattice parameter values decrease when the aluminum is doped and also when the aluminum content is increased. This means that the radius of the aluminum ions (Al ^{3 +} (0.535 Å)) is the vanadium ion (V ^{3 +} (0.64 Å), V ^{4 +} (0.56 Å)) was determined to be smaller than the radius.

The crystal structure of VO _1.52 (OH) _0.77 predicted from the XRD analysis results of FIGS. 4 and 5 may be the same as that of FIG. 1A, and (V _0.95 Al _0.05 ) O _1.52 (OH) _0.77 and (V _0.91 Al _0.09 ) O _1.52. The crystal structure of (OH) _0.77 may be the same as that of FIG. 2.

When Figures 1a and reference again to Figure _{2, VO 1.52 (OH) 0.77,} (V 0. 95 Al 0. 05) O 1 .52 (OH) 0.77 and _{(V 0. 91 Al 0. 09} ) O 1 .52 (OH) _{0. 77} it can be seen that it comprises a 2 × 2 channels in the crystal structure. Such 2 × 2 channels may enable insertion or detachment of monovalent or divalent metal cations.

6 is a SEM photograph of the powder obtained in Preparation Example 1-1.

Referring to FIG. 6, it can be seen that VO _1.52 (OH) _0.77 powder includes particles having an elliptical shape similar to that of rice grains, and the average length of the particles has a relatively homogeneous particle shape of about 0.35 μm.

7 and 8 are SEM pictures of the powder obtained in Preparation Example 1-2 and Preparation Example 1-3, respectively, Figure 9 is a powder obtained in Preparation Examples 1-1, 1-2, and 1-3, respectively Show the TEM pictures taken. Specifically, FIG. 7 shows (V _0.95 Al _0.05 ) O _1.52 (OH) _0.77 powder and FIG. 8 shows (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 powder.

When Fig. 7, see Figure 8, and Figure 9, the Al-ion storage powder doped vanadium arithmetic that _{is, (V 0.95 Al 0.05) O} 1.52 (OH) 0.77 powders or _{(V 0. 91 Al 0. 09} ) O 1 for _.52 (OH) _{0. 77} powder (7, 8, 9) comprises a particle having a shape similar to the oval shape of the grain of rice, like VO _{1 .52} (OH) _0.77 powder. However, VO _1.52 (OH) _0.77 particles (FIGS. 6 and 9) have vanadium oxyhydrate particles doped with Al ions, that is, (V _0.95 Al _0.05 ) O _1.52 (OH) compared to those having a length of 300 to 500 nm. _0.77 If the length of the particles, or _{(V 0. 91 Al 0. 09} ) O 1 .52 (OH) 0.77 particles (7, 8, 9), it can be seen that binary significantly reduced to 50 to 100 ㎚. Further, VO _1.52 (OH) _0.77 Particles (6, 9) 50 to 100, compared to a width of ㎚, Al ions are doped vanadium oxide particle dispersion water that _{is, (V 0. 95 Al 0.} 05) O _{1 .52} (OH) _0.77 in the case of particles or _{(V 0.91 Al 0.09) O 1.52} (OH) 0.77 particles (7, 8, 9), the width can be seen that binary significantly reduced to 20 to 25 ㎚.

10 is a schematic diagram showing ion diffusion distances of VO _1.52 (OH) _0.77 particles (Preparation Example 1-1) and vanadium oxyhydrate particles (Preparation Examples 1-2, 1-3) doped with Al ions.

Referring to FIG. 10, since the vanadium oxyhydrate particles doped with Al ions have a shorter length than the VO _1.52 (OH) _0.77 particles, the ion diffusion distance in the particles may be shortened. When the ion diffusion distance in the active material particles is short, the secondary battery including the same may show a very good performance in the electrochemical measurement evaluation.

FIG. 11 is a graph showing a BET (Brunauer-Emmett-Teller) surface area of Al doping degree of powders obtained in Preparation Examples 1-1, 1-2, and 1-3. The BET surface area was subdivided into powders obtained in Production Examples 1-1, 1-2, and 1-3, respectively, into a glass cylinder for BET, and subjected to a pretreatment (heat treatment) under a vacuum at 200 ° C. to remove moisture. After cooling to room temperature, the BET surface area was measured.

Referring to FIG. 11, VO _1.52 (OH) _0.77 powder (Preparation Example 1-1) has a specific surface area of about 34 m ² / g, but Al ions doped vanadium oxyhydrate powder is an example of (V _{0. 95 Al 0. 05) O} 1 .52 (OH) 0.77 powder (Production example 1-2) it can be seen that a significant increase in the specific surface area to be about 80 ~ 90 m ² / g. This may be understood as the specific surface area of the powder is increased as the particle size decreases as described with reference to the TEM image of FIG. 9. As such, the active material powder having the increased specific surface area may be in contact with the electrolyte in the secondary battery more. Therefore, it can be inferred that the secondary battery containing the active material powder may have improved electrochemical performance.

Preparation Example 2 Preparation of Anode Using Vanadium Oxide

After the vanadium oxyhydrate powder prepared in Preparation Example 1, a conductive material (Super-P, Denka black), and a binder (Poly vinylidene fluoride) were mixed in an organic solvent (NMP (N-Methyl-2-Pyrrolidone)), The electrode of the zinc ion battery was coated on a stainless steel mesh current collector and pressed to form an electrode. The electrode of the lithium and sodium ion battery was coated on an aluminum current collector and pressed to form an anode.

Preparation Example 3 Preparation of Lithium Ion Half-Cell

Using a non-aqueous electrolyte containing a positive electrode, a lithium metal plate as a negative electrode prepared in Preparation Example 2, an electrolyte LiPF ₆ and an organic solvent propylene carbonate (PC, 98 vol.%) And fluoroethylene carbonate (FEC, 2 vol.%) A lithium ion half cell was prepared.

Preparation Example 4 Preparation of Sodium Ion Half-Cell

Using a positive electrode prepared in Preparation Example 2, a sodium metal plate as a negative electrode, and a non-aqueous electrolyte containing NaPF ₆ , an organic solvent propylene carbonate (PC, 98 vol.%) And fluoroethylene carbonate (FEC, 2 vol.%). A sodium ion half cell was prepared.

Preparation Example 5 Preparation of Zinc Ion Half-cell

A zinc ion half-cell was prepared using the positive electrode prepared in Preparation Example 2, a zinc metal plate as a negative electrode, and an aqueous electrolyte solution containing electrolyte ZnSO ₄ and water as a solvent.

Evaluation Example 1 Evaluation of Lithium Ion Half-Cell Characteristics

The lithium ion half cell obtained in Production Example 3 was charged with constant current at 20 mA / g up to 3.7 V, and discharge was performed at 1.5 V with constant current discharge at the same rate as the charging speed. When evaluating the cycle characteristics, charge and discharge proceeded for a total of 20 cycles.

12A and 12B are graphs showing charge and discharge characteristics of a first cycle of a lithium ion half cell obtained through Preparation Example 3 using VO _1.52 (OH) _0.77 positive electrode active material of Preparation Example 1-1, respectively, and showing cycle characteristics. It is a graph.

12A and 12B, a lithium ion half cell prepared using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1 was found to have a discharge capacity of 240 mAh / g in the first cycle. From this, in a lithium ion battery system, it can be seen that access to VO _{1 .52} (OH) _{0. 77} to the positive electrode active material. However, after a total of 20 cycles of charge and discharge, the discharge capacity was lowered to 120mAh / g.

13 is of Preparation _{1-2 (V 0. 95 Al 0.} 05) O 1 .52 (OH) 0.77 charge and discharge characteristics of the lithium ion inversion fingers first cycle obtained from the Preparation Example 3 using the positive electrode active material 14 is a graph showing charge and discharge characteristics of a first cycle of a lithium ion half cell obtained through Preparation Example 3 using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3. The graph shown.

13 and 14, of Preparation _{1-2 (V 0. 95 Al 0.} 05) O 1 .52 (OH) 0.77 the discharge capacity in the first cycle in which the lithium ion reversal produced by using the positive electrode active material this is about 320 mAh / g, Production example 1-3 _{(V 0. 91 Al 0. 09} ) O 1 .52 (OH) 0.77 the discharge capacity in the first cycle in which the lithium ion reversal produced by using the positive electrode active material is It was found to be about 293 mAh / g. From this, it can be seen that the aluminum-doped vanadium oxyhydrate can be used as a positive electrode active material in a lithium ion battery system, and the discharge capacity is higher than that of a lithium ion half cell using vanadium oxyhydrate without aluminum (FIG. 12A). It can be seen that the improvement.

Evaluation Example 2: Sodium Half-cell Cycle Characteristics Evaluation

The sodium ion half cell obtained in Production Example 4 was charged with constant current at 20 mA / g up to 3.7 V, and discharge was performed with constant current discharge up to 1.5 V at the same rate as the charging speed. When evaluating the cycle characteristics, charge and discharge proceeded for a total of 20 cycles.

15A and 15B are graphs showing charge and discharge characteristics of a first cycle of a sodium ion half cell obtained through Preparation Example 4 using VO _1.52 (OH) _0.77 positive electrode active material of Preparation Example 1-1, respectively, and showing cycle characteristics. It is a graph.

Referring to FIGS. 15A and 15B, a sodium ion half cell prepared using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1 was found to have a discharge capacity of 90 mAh / g in the first cycle. In therefrom, sodium lithium ion battery system, it can be seen that access to VO _{1 .52} (OH) _{0. 77} to the positive electrode active material. In addition, even if the charge and discharge cycles were repeated, the discharge capacity hardly decreased, and even after a total of 20 cycles of charge and discharge progress, the discharge capacity was 90 mAh / g similar to the initial discharge capacity. From this, sodium lithium-ion battery system using a VO _1.52 (OH) _{0. 77} to the positive electrode active material can be seen that excellent capacity retention rate.

16 is prepared in Example 1-2 _{(V 0. 95 Al 0. 05} ) O 1 .52 (OH) 0.77 charge and discharge characteristics of the sodium ion reversal fingers first cycle obtained from the Production Example 4 by using the positive electrode active material 17 is a graph showing charge and discharge characteristics of a first cycle of a sodium ion _half cell obtained through Preparation Example 4 using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3. The graph shown.

16 and 17, of Preparation _{1-2 (V 0. 95 Al 0.} 05) O 1 .52 (OH) 0.77 the discharge capacity in the first cycle in which the sodium ion reversal produced by using the positive electrode active material This was about 119 mAh / g, and a sodium ion half cell prepared using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3 had a discharge capacity of about 123 mAh / g in the first cycle. Appeared. From this, it can be seen that the aluminum-doped vanadium oxyhydrate can be used as a positive electrode active material in the sodium ion battery system, and the discharge capacity is higher than that of the sodium ion half cell using vanadium oxyhydrate without aluminum (FIG. 15A). It can be seen that the improvement.

Evaluation Example 3: Evaluation of Zinc Ion Half-cell

The zinc ion half cell obtained in the manufacture example 5 was charged with constant current at 20 mA / g to 1.1V, and discharge was performed with constant current discharge to 0.2V at the same speed as the said charge rate. When evaluating the cycle characteristics, charge and discharge proceeded for a total of 20 cycles.

18A and 18B are graphs showing charge and discharge characteristics of a first cycle of a zinc ion half cell obtained through Preparation Example 5 using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1, respectively, and showing cycle characteristics. It is a graph.

Referring to FIGS. 18A and 18B, a zinc ion half cell prepared using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1 was found to have a discharge capacity of 140 mAh / g in the first cycle. From this, the zinc ion cell system it can be seen that access to VO _{1 .52} (OH) _{0. 77} to the positive electrode active material. However, after a total of 20 cycles of charge and discharge, the discharge capacity was lowered to about 60 mAh / g.

19 is prepared in Example 1-2 _{(V 0. 95 Al 0. 05} ) O 1 .52 (OH) 0.77 charge and discharge characteristics of the zinc ion inversion fingers first cycle obtained from the Production Example 5 by using the positive electrode active material 20 is a graph showing charge and discharge characteristics of a first cycle of a zinc ion half cell obtained in Preparation Example 5 using (V _0.91 Al _0.09 ) O _1.52 (OH) _0.77 cathode active material of Preparation Examples 1-3. The graph shown.

When Figure 19 and Figure 20, Production Example 1-2 _{(V 0. 95 Al 0. 05} ) O 1 .52 (OH) 0.77 the discharge capacity in the first cycle in which the zinc ion reversal produced by using the positive electrode active material and about 155 mAh / g, the preparation of example 1-3 _{(V 0. 91 Al 0. 09} ) O 1 .52 (OH) discharge capacity at the first cycle in which the zinc ions _0.77 reversal produced by using the positive electrode active material It was found to be about 138 mAh / g. From this, it can be seen that the aluminum-doped vanadium oxyhydrate can be used as a positive electrode active material in a zinc ion battery system, and the discharge capacity is similar to that of a zinc ion half cell using vanadium oxyhydrate without aluminum (FIG. 18A). Or more improved.

FIG. 21 is a bond valence sum (BVS) energy map at bc plane of VO _1.52 (OH) _0.77 crystal. FIG. This is the result calculated through density functional theory (DFT) calculation.

Referring to FIG. 21, the diffusion path and insertion position of Li ⁺ , Na ⁺ , and Zn ^{2 +} ions in the VO _1.52 (OH) _0.77 crystal structure can be confirmed by computer simulation. Specifically, the ions may be inserted and diffused in a tunnel structure formed by arranging (V _1-x M _x ) O ₆ octahedrons of VO _1.52 (OH) _0.77 crystal structure in 2 × 2 arrangement.

FIG. 22A illustrates an in situ XRD graph of cathode active materials during an initial cycle of a lithium ion half cell obtained through Preparation Example 3 using VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1, and FIG. 22B is Preparation Example 1 An in-situ XRD graph of the positive electrode active materials is shown in the initial cycle of the sodium ion _half cell obtained in Preparation Example 4 using VO _1.52 (OH) _0.77 positive electrode active material of −1. In the in situ XRD measurement, charging and discharging were performed at a voltage range of 1.5 to 3.7 V and a constant current of 10 mAh.

In addition, Figure 22c shows an X-situ XRD graph of the positive electrode active material during the initial cycle of the zinc ion half cell obtained through Preparation Example 5 using the VO _1.52 (OH) _0.77 cathode active material of Preparation Example 1-1. To this end, two zinc ion half cells were prepared, one of which was discharged to 0.2V, the other was discharged to 0.2V, and then charged to 1.13V, and these two half cells were decomposed and then distilled water was used. The electrode was washed and dried in an 80 degree oven for one day before measuring XRD.

Referring to FIGS. 22A, 22B, and 22C, it can be seen that the XRD peak is shifted in the charging / discharging process, but no new peak occurs. However, the new peak of FIG. 22C was estimated as the peak by the electrolyte. In this way, the charge-discharge procedure i.e., VO _1.52 (OH) _0.77 The lithium ions are only occurs inserted or in the process of desorption VO _1.52 (OH) do not represent a new XRD peak of _0.77 positive electrode active material a shift into the positive electrode active material, lithium ions This means that the crystal structure of the VO _1.52 (OH) _0.77 cathode active material is not affected by insertion or desorption.

Referring to FIGS. 21 and 22A, 22B, and 22C simultaneously, VO _1.52 (OH) _0.77 crystal structure Specifically, ions in a tunnel structure formed by arranging (V _{1- x} M _x ) O ₆ octahedra in 2 x 2 arrays This may simply be inserted and released, and this ion may not change the VO _1.52 (OH) _0.77 crystal structure during charge and discharge.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes by those skilled in the art within the technical spirit and scope of the present invention. This is possible.

Claims (11)

A vanadium oxyhydrate having a tunnel formed by arranging (V _1-x M _x ) O ₆ octahedra in a crystal structure in a 2 × 2 manner, wherein x is greater than 0 and less than or equal to 0.1 and M is +3 or +4 metal Phosphorous electrode active material. The method of claim 1,
M is Al, Si, Cr, or Fe electrode active material. The method of claim 1,
An electrode active material in which oxygen ions are disposed in the tunnel. The method of claim 1,
The tunnel is an electrode active material that can accommodate lithium ions, sodium ions, or zinc ions. An electrode active material comprising the vanadium oxyhydrate represented by the following formula (1).
[Formula 1]
(V _1-x M _x ) O _1.52 (OH) _0.77
In Formula 1, x is greater than 0 and less than or equal to 0.1, and M is a metal having an oxidation number of +3 or +4. The method of claim 5,
M is Al, Si, Cr, or Fe electrode active material. The method of claim 5,
The vanadium oxyhydrate is an electrode active material having a hollandite crystal structure. The method according to claim 1 or 5,
The vanadium oxyhydrate is an electrode active material having a space group (I4 / m). A positive electrode comprising the electrode active material of claim 1 or 5;
A negative electrode containing a negative electrode active material; And
A secondary battery comprising an electrolyte disposed between the positive electrode and the negative electrode. delete A vanadium oxyhydrate having a tunnel formed by arranging VO ₆ octahedrons in a crystal structure in a 2 × 2 manner, wherein oxygen ions are disposed in the tunnel, and metal ions are inserted into the tunnel and include an electrode active material desorbed from the tunnel anode;
A negative electrode containing a negative electrode active material; And
An electrolyte disposed between the positive electrode and the negative electrode,
The metal ion is sodium ion or zinc ion secondary battery.

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