KR102006715B1 - Electrode active material for natrium battery, method for preparing the same, electrode comprising the same, and natrium battery comprising the electrode - Google Patents

Abstract

The present invention relates to an electrode active material for a sodium battery, a method of manufacturing the same, an electrode including the same, and a sodium battery including the electrode, wherein the electrode active material for a sodium battery includes a compound represented by the following Chemical Formula 1.
[Chemical Formula 1]
_{Co 0 .5 Ti 2 (PO 4} ) 3
The electrode active material may reversibly intercalate and deintercalate sodium ions so that the electrode active material may be used as an electrode active material for a sodium battery, and a sodium battery including the electrode active material for a sodium battery may have high charge and discharge efficiency. Capacity is improved.

Description

ELECTRODE ACTIVE MATERIAL FOR NATRIUM BATTERY, METHOD FOR PREPARING THE SAME, ELECTRODE COMPRISING THE SAME, AND NATRIUM BATTERY COMPRISING THE ELECTRODE

The present invention relates to an electrode active material for a sodium battery, a method of manufacturing the same, an electrode including the same, and a sodium battery including the electrode, wherein the sodium ions can be reversibly intercalated and deintercalated. The present invention relates to a sodium battery electrode active material that can be used as an electrode active material for a sodium battery, a method for preparing the same, an electrode including the same, and a sodium battery including the electrode.

As the light weight and high functionalization of portable electronic devices such as video cameras, mobile phones, and notebook PCs are advanced, studies on high capacity and high energy density of batteries used as driving power sources have been conducted.

Lithium batteries are widely used for commercial purposes because energy density per unit weight is about three times higher and faster charging is possible compared to conventional lead acid batteries, nickel-cadmium batteries, nickel hydrogen batteries, and nickel zinc batteries.

Lithium batteries have a safety problem due to the high reactivity of lithium, and lithium element is expensive.

On the other hand, sodium batteries are being actively researched for medium and large battery applications such as electric power storage and electric vehicles because they are more environmentally friendly, have better price competitiveness, and have higher energy storage characteristics than lithium batteries.

As the electrode active material of the sodium battery, a sodium transition metal oxide containing a transition metal such as Mn, Fe, Ni, Co, V, Cr, or the like may be used.

The sodium transition metal oxide has a structural advantage that it has a large theoretical capacity and secures a sufficient channel for transporting sodium ions in the crystal structure, compared to a phosphate containing a polyvalent anion such as phosphate and fluorophosphate.

However, the sodium transition metal oxide has a poor lifespan due to the rapid deterioration of the electrode due to the transition of the crystal structure due to the change of the center metal oxide number during charging and discharging, and the discharge capacity is poor due to the high content of inert sodium in the crystal structure.

Therefore, there is still a need for an electrode active material capable of providing a sodium battery having improved discharge capacity and lifetime characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art, and it is possible to reversibly intercalate and deintercalate sodium ions so that sodium batteries can be used as electrode active materials for sodium batteries. It is to provide an electrode active material.

Another object of the present invention is to provide a method for producing the electrode active material for sodium batteries.

Still another object of the present invention is to provide a sodium battery electrode including the electrode active material for sodium battery.

Another object of the present invention is to provide a sodium battery with improved charge and discharge efficiency and capacity.

According to an embodiment of the present invention, an electrode active material for a sodium battery including the compound represented by the following Chemical Formula 1 is provided.

[Formula 1]

_{Co 0 .5 Ti 2 (PO 4} ) 3

The crystal structure of the compound represented by Formula 1 may be a trigonal system.

The space group of the compound represented by Formula 1 may be R-3c.

The lattice constant of the compound represented by Formula 1 may be 8.31 <a <8.61kV, 3.31 <b <8.61kV, 21.01 <c <21.25kV, α = 90 °, β = 90 °, and γ = 120 °.

According to another embodiment of the present invention, (NH ₄ ) ₂ HPO ₄ , TiC ₁₆ H ₃₆ O ₄ , CoC ₄ H ₆ O ₄ H ₂ O and hydrogen peroxide is added to the solvent to prepare a mixed solution, and After evaporating the solvent, it provides a method for producing an electrode active material for sodium battery comprising the step of firing.

The (NH ₄ ) ₂ HPO ₄ , the TiC ₁₆ H ₃₆ O ₄ , the CoC ₄ H ₆ O ₄ .H ₂ O may be mixed in a molar ratio of 6: 3.7: 1 to 6: 4: 1.5.

The hydrogen peroxide may be added in an amount of 70 to 90 parts by weight based on 100 parts by weight of the (NH ₄ ) ₂ HPO ₄ .

The firing may be performed at 250 to 900 ° C. for 10 to 30 hours.

The firing may be performed at 250 to 500 ° C. for 8 to 12 hours, and then at 800 to 900 ° C. for 8 to 12 hours.

According to another embodiment of the present invention, there is provided a sodium battery electrode comprising the electrode active material for sodium battery.

The sodium battery electrode may include 70 to 90 wt% of the electrode active material based on the total weight of the electrode.

The sodium battery electrode may be any one selected from the group consisting of a positive electrode, a negative electrode, and a combination thereof.

According to another embodiment of the present invention, a sodium battery including the sodium battery electrode is provided.

The electrode active material for a sodium battery of the present invention can be used as an electrode active material for sodium battery because it can reversibly intercalate and deintercalate sodium ions, and the sodium battery comprising the electrode active material for sodium battery The charge and discharge efficiency and capacity are improved.

1 is an exploded perspective view of a sodium battery according to an embodiment of the present invention.
Figure 2 is a graph showing the XRD data of the electrode active material prepared in Example 1 of the present invention.
3 is a scanning electron microscope (SEM) photograph of the electrode active material prepared in Example 1 of the present invention.
Figure 4 is a graph showing the charge and discharge profile of the battery prepared in Example 1 of the present invention.
5 is a graph showing XRD data before and after intercalation of the electrode active material prepared in Example 1 of the present invention.

Hereinafter, the present invention will be described in more detail.

An electrode active material for a sodium battery according to an embodiment of the present invention includes a compound represented by the following Chemical Formula 1.

[Formula 1]

_{Co 0 .5 Ti 2 (PO 4} ) 3

The crystal structure of the compound represented by Formula 1 may be a trigonal system, and the space group of the compound represented by Formula 1 may be R-3c.

In addition, the lattice constant of the compound represented by Formula 1 may be 8.31 <a <8.61Å, 3.31 <b <8.61Å, 21.01 <c <21.25Å, α = 90 °, β = 90 °, γ = 120 ° have.

The compound represented by Chemical Formula 1 having the chemical formula and crystal structure as described above may reversibly intercalate and deintercalate sodium ions.

In addition, the compound represented by Formula 1 may improve the charge and discharge efficiency and capacity of the sodium battery when used as an electrode active material for sodium battery.

In another embodiment of the present invention, a method of manufacturing an electrode active material for a sodium battery includes (NH ₄ ) ₂ HPO ₄ , TiC ₁₆ H ₃₆ O ₄ , CoC ₄ H ₆ O ₄ · H ₂ O, and hydrogen peroxide added to a solvent to be mixed. Preparing a solution, and then evaporating the solvent, followed by calcining.

The (NH ₄ ) ₂ HPO ₄ , the TiC ₁₆ H ₃₆ O ₄ , the CoC ₄ H ₆ O ₄ H ₂ O have a molar ratio of 6: 3.7: 1 to 6: 4: 1.5, preferably 6: 4: It may be mixed in a molar ratio of 1 to 6: 4: 1.2.

When the molar ratio of (NH ₄ ) ₂ HPO ₄ is less than 6, impurities including titanium or cobalt may be generated, and when more than 6, impurities including phosphorus may be generated.

When the molar ratio of TiC ₁₆ H ₃₆ O ₄ is less than 3.7, impurities containing phosphorus or cobalt may be generated, and when it exceeds 4, impurities including titanium may be generated. When the molar ratio of CoC ₄ H ₆ O ₄ .H ₂ O is less than 1, an impurity including phosphorus or titanium may be generated, and when more than 1.5, an impurity including cobalt may be generated.

The hydrogen peroxide may be added in an amount of 70 to 90 parts by weight based on 100 parts by weight of the (NH ₄ ) ₂ HPO ₄ . When the content of the hydrogen peroxide is less than 70 parts by weight of the precursor may not be sufficient due to the oxidation reaction of the precursor may occur, if the content exceeds 90 parts by weight may occur for too short time.

The firing may be performed at 250 to 900 ° C. for 10 to 30 hours, preferably at 300 to 850 ° C. for 10 to 20 hours. Impurities may occur when the firing temperature is lower than 250 ° C., and when the firing temperature is higher than 900 ° C., there may be a problem in that other materials are produced or the size of the synthesized material is too large.

At this time, the firing is performed for 8 to 12 hours at 250 to 500 ℃, preferably for 10 to 12 hours at 300 to 350 ℃, then for 8 to 12 hours at 800 to 900 ℃, preferably 800 to 850 ℃ 10 to 12 hours, such as may proceed through a plurality of steps.

A sodium battery electrode according to another embodiment of the present invention includes the sodium battery electrode active material. The sodium battery electrode may be any one selected from the group consisting of a positive electrode, a negative electrode, and a combination thereof. That is, the electrode active material for sodium battery may be a positive electrode active material, or may be a negative electrode active material.

In addition, the sodium battery according to another embodiment of the present invention includes the sodium battery electrode. The sodium battery may be a primary battery or a secondary battery. Hereinafter, the case where the sodium battery is a secondary battery will be mainly described, but the present invention is not limited thereto.

Specifically, the sodium battery includes a positive electrode including a positive electrode active material disposed opposite to each other, a negative electrode including a negative electrode active material, and a separator interposed between the positive electrode and the negative electrode.

1 is an exploded perspective view of one embodiment of the sodium battery 1. 1 is only an example for describing the present invention and the present invention is not limited thereto.

Referring to FIG. 1, in the sodium secondary battery 1, a separator 7 is disposed between the negative electrode 3, the positive electrode 5, the negative electrode 3, and the positive electrode 5 to form an electrode assembly 9. It can be prepared by placing in the case 15 and injecting an electrolyte (not shown) so that the negative electrode 3, the positive electrode 5 and the separator 7 is impregnated in the electrolyte.

Conductive lead members 10 and 13 may be attached to the negative electrode 3 and the positive electrode 5, respectively, and the lead members 10 and 13 may be attached to the positive electrode 5, respectively. And a current generated in the negative electrode 3 to the positive electrode terminal and the negative electrode terminal.

First, the anode 5 may be prepared as follows, for example.

For example, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on a metal current collector to prepare a positive electrode plate. Alternatively, the cathode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to prepare a cathode plate. The positive electrode 5 is not limited to the above-listed forms but may have a form other than the above.

The positive electrode 5 may include an electrode active material for a sodium battery according to an embodiment of the present invention.

In addition, the positive electrode 5 may further include a conventional general positive electrode active material in addition to the sodium battery electrode active material according to an embodiment of the present invention, the electrode active material for sodium battery according to an embodiment of the present invention is a negative electrode active material When used as, the conventional cathode active material may be used as the cathode active material.

The conventional general cathode active material may be used without limitation as long as it is a material capable of intercalating / deintercalating sodium, and specifically, NaM ¹ _a O ₂ such as NaFeO ₂ , NaMnO ₂ , NaNiO _2, and NaCoO ₂ . is _{oxide, Na 0 .44 Mn 1 - a} M 1 a O oxide represented by _{2, Na 0.7 Mn 1-a} M 1 a O oxide represented by _2.05 (M ¹ is a transition metal element at least one, 0≤a <1); Oxides represented by Na _b M ² _c Si ₁₂ O ₃₀ , such as Na ₆ Fe ₂ Si ₁₂ O ₃₀ and Na ₂ Fe ₅ Si ₁₂ O ₃₀ (M ² is one or more transition metal elements, 2 ≦ b ≦ 6, 2 ≤ c ≤ 5); Oxides represented by Na _d M ³ _e Si ₆ O ₁₈ , such as Na ₂ Fe ₂ Si ₆ O ₁₈ and Na ₂ MnFeSi ₆ O ₁₈ (M ³ is one or more transition metal elements, 3 ≦ _d ≦ _{6, 1} ≦ _e ≤2); Oxides represented by Na _f M ⁴ _g Si ₂ O ₆ , such as Na ₂ FeSiO ₆ (M ⁴ is at least one element selected from the group consisting of transition metal elements, Mg and Al, 1 ≦ f ≦ 2, 1 ≦ g ≤2); Phosphates such as NaFePO ₄ and Na ₃ Fe ₂ (PO ₄ ) ₃ ; Borate salts such as NaFeBO ₄ and Na ₃ Fe ₂ (BO ₄ ) ₃ ; Fluorides represented by Na _h M ⁵ F ₆ , such as Na ₃ FeF ₆ and Na ₂ MnF ₆ (M ⁵ may be one or more transition metal elements, ₂ ≦ _h ≦ 3), but are not limited thereto. As long as it can be used in the art and does not deteriorate the performance of a sodium battery, it is possible.

As the conductive material, a mixture of one or two or more carbon materials having a high specific surface area, for example, carbon black, activated carbon, acetylene black, and graphite fine particles can be used. In addition, electrically conductive fibers such as carbon grown from vapor-grown carbon or pitch (byproduct of petroleum, coal, coal tar, etc.) at high temperature, and carbon fibers made from acrylic fiber (Polyacrylonitrile) can also be used as the conductive material. . Carbon fiber and high specific surface area carbon material can be used at the same time. The electrical conductivity can be further improved by simultaneously using the carbon fiber and the carbon material having a high specific surface area. Moreover, it is a material which does not melt | dissolve and melt | dissolve in the charge / discharge range of a positive electrode, and can use the metal-type electrically conductive material of low electrical resistance compared with a positive electrode active material. For example, corrosion resistant metals such as titanium and gold, carbides such as SiC or WC, and nitrides such as Si ₃ N ₄ and BN may be used, but are not limited thereto and may be used as conductive materials in the art. Do.

As the binder, a polymer of a fluorine compound (ie, a fluorine-based polymer) may be used. The fluorine compound is, for example, alkyl fluoride (C1-C18) (meth) acrylate, perfluoroalkyl (meth) acrylate (for example, perfluorododecyl (meth) acrylate, perfluoro n-octyl (meth) acrylate, perfluoro n-butyl (meth) acrylate, perfluoroalkyl substituted alkyl (meth) acrylate (e.g., perfluorohexylethyl (meth) acrylate, purple Urooctylethyl (meth) acrylate, perfluorooxyalkyl (meth) acrylate (eg, perfluorododecyloxyethyl (meth) acrylate and perfluorodecyloxyethyl (meth) acrylate Etc.), fluorinated alkyl (C1-C18) crotonate, fluorinated alkyl (C1-C18) maleate, fluorinated alkyl (C1-C18) maleate fumarate, fluorinated alkyl (C1-C18) itaconate, fluorinated alkyl substitution Olefins (2-10 carbon atoms, 1-17 fluorine atoms), for example, perfluorohexylethylene, Ethylene, trifluoro-fluorinated olefin, tetrafluoroethylene to carbon double bond a small number of about 2 to about 10 and 1 to 20 fluorine atoms bonded fluorine atoms with ethylene, vinylidene fluoride or hexafluoro-propylene and the like can be used.

As the binder, a copolymer of a fluorine compound and a monomer containing an ethylenic double bond containing no fluorine atom can be used.

In addition, a non-fluorine-based polymer can be used as the binder.

The non-fluorine-based polymer is a polymer that does not contain fluorine. For example, the non-fluorine-based polymer may be an addition polymer of a monomer containing an ethylenic double bond containing no fluorine atom. Such monomers are, for example, (cyclo) alkyl (C1-C22) (meth) acrylates (for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso Butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.) ; Aromatic ring-containing (meth) acrylates (eg, benzyl (meth) acrylate, phenylethyl (meth) acrylate, etc.); Mono (meth) acrylate (for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate) of alkylene glycol or dialkylene glycol (C2-C4 of an alkylene group) , Diethylene glycol mono (meth) acrylate); (Poly) glycerol (polymerization degree 1 to 4) mono (meth) acrylate; Multifunctional (meth) acrylate [For example, (poly) ethylene glycol (polymerization degree 1-100) di (meth) acrylate, (poly) propylene glycol (polymerization degree 1-100) di (meth) acrylate, 2, (Meth) acrylic acid ester monomers such as 2-bis (4-hydroxyethylphenyl) propanedi (meth) acrylate and trimethylolpropane tri (meth) acrylate); (Meth) acrylamide monomers, such as (meth) acrylamide and (meth) acrylamide derivatives (for example, N-methylol (meth) acrylamide, diacetone acrylamide, etc.); Cyano group-containing monomers such as (meth) acrylonitrile, 2-cyanoethyl (meth) acrylate and 2-cyanoethylacrylamide; Styrene monomers such as styrene and styrene derivatives having 7 to 18 carbon atoms (for example, α-methylstyrene, vinyltoluene, p-hydroxystyrene and divinylbenzene); Diene monomers such as alkadienes having 4 to 12 carbon atoms (for example, butadiene, isoprene, chloroprene and the like); Carboxylic acid (C2-C12) vinyl ester (for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octanoate, etc.), carboxylic acid (C2-C12) (meth) allyl ester (for example, acetic acid ( Alkenyl ester monomers such as meta) allyl, propionic acid (meth) allyl and octanoic acid (meth) allyl); Epoxy group-containing monomers such as glycidyl (meth) acrylate and (meth) allyl glycidyl ether; Monoolefins having 2 to 12 carbon atoms (eg, ethylene, propylene, 1-butene, 1-octene, 1-dodecene, etc.); Halogen atom-containing monomers other than fluorine such as chlorine, bromine or iodine atom-containing monomers, vinyl chloride and vinylidene chloride; (Meth) acrylic acid, such as acrylic acid and methacrylic acid; Conjugated double bond-containing monomers such as butadiene and isoprene. For example, it may be polyethylene, polypropylene, and the like. The addition polymer may be, for example, a copolymer such as ethylene-vinyl acetate copolymer, styrene-butadiene copolymer or ethylene-propylene copolymer.

The carboxylic acid vinyl ester polymer may also be partially or fully saponified, such as polyvinyl alcohol and the like.

As the binder, for example, polysaccharides and derivatives thereof such as starch, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl hydroxyethyl cellulose and nitrocellulose; Phenol resins; Melamine resins; Polyurethane resins; Urea resins; Polyamide resins; Polyimide resins; Polyamideimide resin; Petroleum pitch; Coal pitch and the like can be used. A plurality of binders can be used as the binder.

In addition, the binder may act as a thickener in the electrode mixture.

Specifically, the binder is vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene and mixtures thereof or styrene butadiene rubber-based polymers. Etc. may be used, but the present invention is not limited thereto, and all may be used as long as the binder can be used in the art.

N-methylpyrrolidone, acetone or water may be used as the solvent, but is not limited thereto, and any solvent may be used as long as it can be used in the art.

As the current collector, for example, metals such as nickel, aluminum, titanium, copper, gold, silver, platinum, aluminum alloy or stainless steel, for example, carbon materials, activated carbon fibers, nickel, aluminum, zinc, copper, tin, Lead formed by plasma spraying or arc spraying these alloys, for example, a conductive film in which a conductive agent is dispersed in a resin such as rubber or styrene-ethylene-butylene-styrene copolymer (SEBS) can be used. For example, aluminum, nickel or stainless steel may be used. In particular, aluminum may be used in that it is easy and inexpensive to process into a thin film. The shape of the current collector is not particularly limited, and for example, a thin film, a flat plate, a mesh, a net, a punched or embossed form, or a combination thereof (for example, a mesh plate) can be used. have. For example, the unevenness | corrugation by an etching process can be formed in the surface of an electrical power collector.

The content of the positive electrode active material, the conductive material, the binder, and the solvent in the positive electrode 5 is at a level commonly used in sodium batteries. At least one of the conductive material, the binder, and the solvent may be omitted according to the use and configuration of the sodium battery.

However, when the positive electrode active material includes the electrode active material for sodium batteries of the present invention, the positive electrode 5 includes the electrode active material in an amount of 90 to 70% by weight, preferably 80 to 75% by weight, based on the total weight of the electrode. can do. When the content of the electrode active material is less than 70% by weight relative to the total weight of the electrode, a side reaction may occur, and when it exceeds 90% by weight, conductivity may be reduced.

Next, the cathode 3 is prepared.

In the sodium battery, the negative electrode 3 may include an electrode active material for a sodium battery according to an embodiment of the present invention.

In addition, the negative electrode 3 may further include a conventional general negative electrode active material in addition to the sodium battery electrode active material according to an embodiment of the present invention, the electrode active material for sodium battery according to an embodiment of the present invention is a positive electrode active material When used as, the conventional negative electrode active material may be used as the negative electrode active material.

The conventional general negative electrode active material may include sodium metal, sodium metal-based alloy, sodium intercalating compound or carbon-based material, but is not necessarily limited to these and can be used as a negative electrode active material in the art Anything that includes sodium or that can intercalate / deintercalate sodium is possible.

Since the negative electrode 3 determines the capacity of the sodium battery 1, the negative electrode 3 may be, for example, sodium metal. Examples of the sodium metal-based alloys include alloys of aluminum such as aluminum, tin, indium, calcium, titanium, vanadium, and sodium.

For example, the cathode 3 may be generally used in the form of sodium in a metal state having a thickness of 3 μm to 500 μm, and may be used in various forms such as film, sheet, foil, net, porous body, foam, and nonwoven fabric. have.

In the case of using a negative electrode active material other than the sodium metal or the sodium alloy, a carbon-based material having a graphene structure or the like can be used. Mixed cathodes of materials such as graphite and graphitized carbon, mixed cathodes of carbon-based materials and metals or alloys, and composite cathodes can be used. Examples of the carbonaceous material include natural graphite, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor growth carbon fiber, pitch carbonaceous material, needle coke, petroleum coke, Carbonaceous materials such as polyacrylonitrile-based carbon fibers and carbon black, or amorphous carbon materials synthesized by pyrolysis of 5- or 6-membered cyclic hydrocarbons or cyclic oxygen-containing organic compounds may be used.

When the negative electrode active material is in powder form, the negative electrode 3 may be prepared as follows. The negative electrode 3 may be manufactured by the same method as the positive electrode 5 except for using the negative electrode active material instead of the positive electrode active material. In the negative electrode active material composition, the same conductive material, binder, and solvent may be used as the positive electrode.

For example, a negative electrode active material, a conductive material, a binder, and a solvent may be mixed to prepare a negative electrode active material composition, and the negative electrode 3 may be manufactured by directly coating the negative electrode active material. Alternatively, the negative electrode 3 may be manufactured by casting the negative electrode active material composition on a separate support and laminating the negative electrode active material film peeled from the support to a copper current collector.

As the negative electrode current collector, any current collector can be used without being limited to a material, a shape, a manufacturing method, or the like. For example, a copper foil having a thickness of 10 to 100 µm, a copper perforated foil having a thickness of 10 to 100 µm, a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal sheet, or the like can be used. In addition to copper, stainless steel, titanium, nickel, or the like may be used as the material of the negative electrode current collector.

The content of the negative electrode active material, the conductive material, the binder, and the solvent in the negative electrode 3 is at a level commonly used in sodium batteries. However, when the negative electrode active material includes the electrode active material for sodium batteries of the present invention, the negative electrode 3 includes the electrode active material in an amount of 70 to 90% by weight, preferably 80 to 75% by weight, based on the total weight of the electrode. can do. When the content of the electrode active material is less than 70% by weight relative to the total weight of the electrode, a side reaction may occur, and when it exceeds 90% by weight, conductivity may be reduced.

The sodium battery 1 may include a separator 7 interposed between the positive electrode 5 and the negative electrode 3.

The separator 7 is not limited so long as it is a composition that can withstand the environment in which the sodium battery 1 is used. For example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, polyethylene or polypropylene The porous films of olefin resins, such as these, can be illustrated, It is also possible to use these 2 or more types together.

In addition, the separator 7 may be used that is low in resistance to ion migration of the electrolyte and excellent in electrolyte moistening ability. For example, it is selected from glass fiber, polyester, Teflon, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in a nonwoven or woven form.

For example, the separator 7 can be manufactured according to the following method.

A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separator composition may be directly coated and dried on the anode active material layer to form the separator 7. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled off from the support may be laminated on the negative electrode active material layer to form a separator 7.

The polymer resin used to manufacture the separator 7 is not particularly limited, and any materials used for the binder of the electrode plate may be used. For example, polyethylene, polypropylene, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or mixtures thereof and the like can be used. Inorganic particles may be used as the filler used to manufacture the separator (7), and the solvent may dissolve the polymer resin and form pores in the polymer resin during drying, as long as it is generally used in the art. All is possible.

In addition, the separator 7 may be separately manufactured by another publicly known method and laminated on the anode active material layer. For example, polypropylene and polyethylene are melted and extruded to form a film, followed by annealing at low temperature and growing a crystal domain, followed by stretching in this state to extend the amorphous region to form a microporous membrane. This can be used. For example, after mixing other low molecular weight materials, such as a hydrocarbon solvent, and polypropylene, polyethylene, etc., the film was formed, and then the film in which the solvent or low molecular weight gathered amorphously and started to form an island phase is mentioned above. A wet manufacturing method may be used in which the microporous membrane is formed by removing the solvent or the low molecule using another volatile solvent.

In addition, the separator 7 may further contain additives such as non-conductive particles, other fillers, and fiber compounds for the purpose of controlling strength, hardness, and heat shrinkage rate. For example, the separator may additionally include inorganic particles. By additionally including the inorganic particles, oxidation resistance of the separator can be improved, and deterioration of battery characteristics can be suppressed. The inorganic particles may be alumina (Al ₂ O ₃ ), silica (SiO ₂ ), titania (TiO ₂ ), or the like.

The average particle diameter of the inorganic particles may be 10nm to 5㎛. If the average particle diameter is less than 10 nm, the crystallinity of the inorganic particles is lowered and the effect of addition is insignificant. If the average particle diameter exceeds 5 μm, dispersion of the inorganic particles may be difficult.

The separator 7 may have a multilayer structure including one or more polymer layers in order to increase tear strength or mechanical strength. For example, it may be a polyethylene / polypropylene laminate, a polyethylene / polypropylene / polyethylene laminate, a nonwoven / polyolefin laminate, and the like.

Next, the electrolyte is prepared.

The electrolyte is a liquid containing sodium in an ionic state, in which a sodium salt serving as an electrolyte is dissolved in a solvent. The battery may be constituted by an organic electrolyte using an organic solvent.

The sodium salt used as the electrolyte is, for example, NaClO ₄ , NaPF ₆ , NaBF ₄ , NaCF ₃ SO ₃ , NaN (CF ₃ SO ₂ ) ₂ , NaN (C ₂ F ₅ SO ₂ ) ₂ , NaC (CF ₃ SO ₂ ) ₃ and the like may be used, but are not necessarily limited thereto, and any of those capable of being used as sodium salt in the art may be used. For example, in the salt used as a lithium salt of a lithium battery, a lithium substituted with sodium may be used.

The concentration of the electrolyte in the organic electrolyte can be appropriately set in consideration of the solubility of the electrolyte in the electrolyte. For example, the concentration of the electrolyte may be 0.1 to 5M. For example, the concentration of the electrolyte may be 0.3 to 3M. For example, the concentration of the electrolyte may be 0.8 to 1.5M. When the concentration of the electrolyte is 0.1M or more, the ionic conductivity of the electrolyte may be increased, and the internal resistance of the sodium battery 1 may be lowered. When the concentration of the electrolyte is 5M or less, the viscosity of the electrolyte may be lowered and the internal resistance of the sodium battery 1 may be lowered. have.

As the organic solvent for dissolving the electrolyte, a polar organic solvent may be used. The water content of the electrolyte including the polar organic solvent may be 200 ppm or less. For example, the moisture content of the electrolyte including the polar organic solvent may be 50 ppm or less. For example, the moisture content of the electrolyte including the polar organic solvent may be 20 ppm or less. By suppressing the water content in the electrolyte containing the polar organic solvent, it is possible to suppress the influence of the water on the electrode due to electrolysis, in particular, the drop in voltage.

As the organic solvent in the organic electrolyte, an aprotic organic solvent can be used. For example, the organic electrolyte for the sodium battery 1 is dimethyl ether, diethyl ether, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylene carbonate, propylene carbonate, Butylene carbonate, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone ( mevalonolactone), caprolactone, dibutyl ether, tetraglyme, diglyme, polyethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,2-dimethyltetrahydrofuran, 2,5-dimethyl Tetrahydrofuran, cyclohexanone, triethylamine, triphenylamine, triether phosphine oxide And one or more organic solvents selected from the group consisting of acetonitrile, dimethylformamide, 1,3-dioxolane, and sulfolane, but are not necessarily limited thereto and may be used as organic solvents in the art. Anything is possible.

In the present embodiment, the cylindrical sodium battery 1 has been described as an example, but the technique of the present invention is not limited to the cylindrical sodium battery 1, and may be any shape as long as it can operate as a battery.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

( Example  One)

Manufacturing example  1: Preparation of Electrode Active Material

_{(NH 4) 2 HPO 4 1.5847g} , TiC 16 H 36 O 4 2.7782g and _{CoC 4 H 6 O 4 · H} 2 O 0.4982g ( molar ratio = 6: 4: 1) were dissolved in DI water of 75ml, 2ml of H ₂ O ₂ (80 parts by weight based on 100 parts by weight of (NH ₄ ) ₂ HPO ₄ ) was added.

After evaporation of all of the DI water, for 10 hours in 300 ℃ in the furnace, and was fired for 10 hours in 800 ℃ was prepared an electrode active material represented by _{Co 0 .5 Ti 2 (PO 4} ) 3.

Manufacturing example  2: Manufacture of batteries

The electrode active material prepared in Preparation Example 1, Super P as a conductive material, Polyacrylonitrile (PAN) as a binder is added to NMP (N-methylpyrrolidone) in a weight ratio of 8: 1: 1, and The positive electrode active material slurry was prepared by mixing. The slurry was coated on a 15 μm thick aluminum foil (Al foil) to a thickness of 40 μm and dried at 120 ° C. for 2 hours in a vacuum oven to prepare a working electrode.

The working electrode was placed in a Teflon container, activated carbon was used as a counter electrode, and glass fiber was used as a separator interposed between the working electrode and the counter electrode. Ag / AgCl (Ag ⁺ ) was used as an electrode, and a battery was constructed using an organic electrolyte solution in which 1 M Na (ClO ₄ ) was dissolved in AC (acetonitrile) as an electrolyte. The inside of the Teflon vessel is an argon atmosphere and sealed to block air.

[ Experimental Example  1: Measurement of Characteristics of Electrode Active Material and Battery]

XRD data of the electrode active material prepared in Preparation Example 1 was measured, and the results are shown in FIG. 2. In addition, a scanning electron microscope (SEM) photograph of the electrode active material prepared in Preparation Example 1 is shown in FIG. 3.

Referring to the Figs. 2 and 3, it can be seen that the Preparation Example 1, clerical script _{Co 0 .5 Ti 2 (PO 4} ) an electrode active material is prepared represented by _3.

The charge and discharge test under 0.1C conditions of the battery prepared in Preparation Example 2 was carried out to measure the voltage profile, and the results are shown in FIG. 4. In addition, XRD data before and after intercalation of sodium ions of the electrode active material prepared in Preparation Example 1 were measured, and the results are shown in FIG. 5.

Referring to FIGS. 4 and 5, it can be seen that sodium ions are reversibly intercalated (desorbed) and deintercalated (released) in the electrode active material, thereby being used as an electrode active material of a sodium battery.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of right.

1: sodium battery
3: cathode
5: anode
7: Separator
9: electrode assembly
10, 13: lead member
15: case

Claims (13)

To include a compound represented by the formula (1),
The crystal structure of the compound represented by Chemical Formula 1 is a trigonal system, and the lattice constant is 8.31 <a <8.611, 3.31 <b <8.61Å, 21.01 <c <21.25Å, α = 90 °, β = An electrode active material for sodium battery, 90 ° and γ = 120 °:
[Chemical Formula 1]
Co _0.5 Ti ₂ (PO ₄ ) _3. delete The method of claim 1,
The space group of the compound represented by Formula 1 is R-3c, the electrode active material for sodium batteries. delete _{(NH 4) 2 HPO 4,} TiC 16 H 36 O 4, CoC 4 H 6 O 4 · the method comprising the addition of H ₂ O and hydrogen peroxide in a solvent to prepare a mixed solution, and
After evaporating the solvent, calcining
A method of producing an electrode active material for sodium batteries according to claim 1. The method of claim 5,
The (NH _{4) 2} HPO _4, wherein the TiC ₁₆ H ₃₆ O _4, the _{CoC 4 H 6 O 4 · H} 2 O 6: 3.7: 1 to 6: 4: that would be mixed with a 1.5 molar sodium cell electrode Method for producing an active material. The method of claim 5,
The hydrogen peroxide is added to 70 to 90 parts by weight based on 100 parts by weight of the (NH ₄ ) ₂ HPO ₄ The manufacturing method of the electrode active material for sodium batteries. The method of claim 5,
The firing is a method for producing an electrode active material for sodium battery that is made for 10 to 30 hours at 250 to 900 ℃. 9. The method of claim 8,
The firing is performed for 8 to 12 hours at 250 to 500 ℃, and then a method for producing an electrode active material for a sodium battery which is made for 8 to 12 hours at 800 to 900 ℃. A sodium battery electrode comprising the electrode active material for sodium batteries according to claim 1. The method of claim 10,
The sodium battery electrode is a sodium battery electrode comprising the electrode active material in 70 to 90% by weight relative to the total weight of the electrode. The method of claim 10,
The sodium battery electrode is any one selected from the group consisting of a positive electrode, a negative electrode and a combination thereof. A sodium battery comprising the electrode for sodium batteries according to claim 10.

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