KR102276170B1 - Sodium Secondary Battery Including Cathode Unified with Collector - Google Patents

Abstract

The present invention relates to a sodium secondary battery, and more particularly, a sodium secondary battery according to an embodiment of the present invention includes a negative electrode containing sodium; A current collector integrated positive electrode comprising a positive electrode active material, a sintered body having a current collector embedded therein; an anolyte in which the positive electrode is charged; and a sodium ion conductive solid electrolyte for separating the anode and the anolyte.

Description

Sodium Secondary Battery Including Cathode Unified with Collector

The present invention relates to a sodium secondary battery, and more particularly, to a sodium secondary battery including a current collector-integrated positive electrode in which a positive electrode and a current collector are integrally formed.

As the use of renewable energy is rapidly increasing, the need for an energy storage device using a battery is rapidly increasing. Among these batteries, a lead battery, a nickel/hydrogen battery, a vanadium battery, and a lithium battery may be used. However, lead batteries and nickel/hydrogen batteries have very small energy densities, so there is a problem that requires a lot of space to store energy of the same capacity. In addition, in the case of vanadium batteries, environmental pollutants due to the use of a solution containing heavy metals and a small amount of material between the negative electrode and the positive electrode move through the membrane separating the negative electrode and the positive electrode, thereby reducing the performance. It cannot be commercialized. In the case of a lithium battery having very excellent energy density and output characteristics, it is technically very advantageous, but due to the resource scarcity of the lithium material, it has a problem that it is not economical to use as a secondary battery for large-scale power storage.

In order to solve this problem, there have been many attempts to use the resource-rich sodium on the earth as a material for secondary batteries. Among them, as in US Patent Publication No. 20030054255, a sodium-sulfur battery in which beta-alumina having selective conductivity for sodium ions is used, sodium is supported on the negative electrode, and sulfur is supported on the positive electrode is currently used as a large-scale power storage device. .

However, conventional sodium-based secondary batteries such as sodium-sulfur batteries have a disadvantage in that they have an operating temperature of at least 300° C. or higher in the case of sodium-sulfur batteries in consideration of conductivity and the melting point of battery components. Due to these problems, there are many disadvantages in terms of economic feasibility in terms of manufacturing or operation in order to maintain temperature, maintain airtightness, and reinforce safety aspects.

In order to solve the above problems, a room temperature type sodium-based battery has been developed, but the output is very low, so the competitiveness is very low compared to a nickel-hydrogen battery or a lithium battery.

US Patent Publication No. 20030054255

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sodium secondary battery capable of low-temperature operation and having a high output by overcoming the problems of conventional high-temperature operation and thermal management.

Another object of the present invention is to provide a sodium secondary battery having reduced internal resistance and stably maintaining electrical conduction even during repeated battery charging and discharging operations.

A sodium secondary battery according to the present invention includes a negative electrode containing sodium; A current collector integrated positive electrode comprising a positive electrode active material, a sintered body having a current collector embedded therein; anolyte in which the anode is charged; and a sodium ion conductive solid electrolyte that separates the anode and the anolyte.

In the sodium secondary battery according to an embodiment of the present invention, the current collector is a conductive material foam (foam), foil (film), mesh (mesh), felt (felt), porous foil (perforated film), film (film) ), rods and wires may be selected from one or more.

In the sodium secondary battery according to an embodiment of the present invention, at least one end of the current collector may protrude out of the sintered body and be connected to a conductive member for electrical connection with the outside of the battery.

In the sodium secondary battery according to an embodiment of the present invention, the current collector embedded in the sintered body may be in a wrinkled state.

In the sodium secondary battery according to an embodiment of the present invention, the current collector embedded in the sintered body may be in a state having a helical structure.

In the sodium secondary battery according to an embodiment of the present invention, the sintered body may have a columnar shape or a hollow columnar shape.

In the sodium secondary battery according to an embodiment of the present invention, two or more current collectors may be arranged to be spaced apart from each other in the sintered body.

In the sodium secondary battery according to an embodiment of the present invention, the porosity (apparent porosity) of the sintered body may be 50 to 75%.

In the sodium secondary battery according to an embodiment of the present invention, the cathode active material includes a cathode active metal, which is at least one metal selected from a transition metal and a group 12 to 14 metal; Or a halide of the positive electrode active metal; may contain.

In the sodium secondary battery according to an embodiment of the present invention, the cathode active material may further contain sodium halide.

In the sodium secondary battery according to an embodiment of the present invention, the anolyte may contain a sodium salt satisfying the following formula (1).

(Formula 1)

NaM(X ₁ ) _n (X ₂ ) _4-n

In Formula 1, M is an element selected from the group of metals and metalloids having a trivalent oxidation number, X ₁ and X ₂ are different halogen elements, and n is a real number with 0≤n≤4.

In the sodium secondary battery according to an embodiment of the present invention, X ₁ and X ₂ are chlorine (Cl) and iodine (I), and n may be 2.0 to 3.8.

In the sodium secondary battery according to an embodiment of the present invention, X ₁ and X ₂ are chlorine (Cl) and bromine (Br), and n may be 0.2 to 3.8.

In the sodium secondary battery according to an embodiment of the present invention, the positive electrode active metal is titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel ( Ni), copper (Cu), zinc (Zn), aluminum (Al), cadmium (Cd), and tin (Sn) may be selected from one or two or more.

The sodium secondary battery according to an embodiment of the present invention may be charged according to the following Reaction Formula 1 and discharged according to the following Reaction Formula 2.

(Scheme 1)

mNaX+M _act → mNa+M _act X _m

In Scheme 1, NaX is sodium halide, M _act is a positive electrode active metal, and m is a natural number of 1 to 4.

(Scheme 2)

mNa+M _act X _m → mNaX+M _act

In Scheme 2, M _act is a positive electrode active metal, M _act X is a halide of a positive electrode active metal, and m is a natural number of 1 to 4.

The sodium secondary battery according to the present invention has the advantage of having a small contact resistance between the positive electrode active material and the current collector, and has the advantage of maintaining a stable electrical and physical connection despite the volume change in the positive electrode that occurs during the charging/discharging reaction of the battery. In addition, it is possible to operate at a low temperature of 100 to 200 ℃, has the advantage of having a high energy density despite the low temperature operation, it is easy to solve the problem of thermal stability and heat sealing according to the operation at a relatively low temperature, airtightness There is an advantage in that the container design conditions for maintenance are more relaxed, and the thermal energy required to maintain the temperature is reduced, thereby increasing economic efficiency.

1 is a view showing a perspective view of a current collector-integrated positive electrode in a sodium secondary battery according to an embodiment of the present invention;
2 is a view showing another perspective view of a current collector-integrated positive electrode in a sodium secondary battery according to an embodiment of the present invention;
3 is a view showing another perspective view of a current collector-integrated positive electrode in a sodium secondary battery according to an embodiment of the present invention;
4 is a view showing another perspective view of a current collector-integrated positive electrode in a sodium secondary battery according to an embodiment of the present invention;
5 is a cross-sectional view illustrating a cross-section of a sodium secondary battery according to an embodiment of the present invention.

Hereinafter, a sodium secondary battery of the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used, it has the meaning commonly understood by those of ordinary skill in the technical field to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted.

A sodium secondary battery according to the present invention includes a negative electrode containing sodium; A current collector integrated positive electrode comprising a positive electrode active material, a sintered body having a current collector embedded therein; anolyte in which the anode is charged; and a sodium ion conductive solid electrolyte that separates the anode and the anolyte.

The secondary battery according to an embodiment of the present invention may have a remarkably small contact resistance between the positive electrode active material involved in the battery reaction and the current collector during a battery charging/discharging reaction due to the current collector integrated positive electrode. That is, as it has a low contact resistance between the positive electrode active material and the current collector, there is an advantage of having a small internal resistance of the battery. Furthermore, there is an advantage in that stable contact between the positive electrode active material and the current collector can be continuously made in spite of a change in volume caused to the positive electrode active material according to the change in the state of charging and discharging. In addition, by increasing the area and/or volume of the current collector located inside the sintered body, there is an advantage in that the contact area between the current collector and the positive electrode active material can be improved.

In an embodiment of the present invention, the sintered body may refer to a sintered body in which an electrode material including a positive electrode active material is compression molded into a predetermined shape by physical pressure and then sintered by heat treatment. Accordingly, the current collector-integrated positive electrode may be a single body in which the current collector is positioned within the positive electrode active material and bonded to each other between the positive electrode active material and the positive electrode active material and the current collector.

As described above, as the current collector-integrated positive electrode is impregnated in the anolyte, open pores present in the sintered body may affect the contact area between the positive electrode and the positive electrode active material. The sintered compact according to an embodiment of the present invention may have a porosity of 50 to 75%, specifically 60 to 70%. In this case, the porosity may mean a ratio of the volume occupied by the open pores among the volume of the sintered body, and may mean the apparent porosity. A porosity of 50 to 75% can withstand the physical impact applied to the positive electrode integrated with the current collector when manufacturing or driving the battery, and while it can have a strong binding force between the current collector and the positive electrode active material, a large amount of the anolyte penetrates the positive electrode with the current collector integrated. range that can be done. The porosity of the sintered body may be adjusted by controlling process factors such as pressure applied during compression molding and heat treatment temperature or time for sintering.

As described above, since the current collector-integrated positive electrode is a sintered body in which the current collector is provided, the current collector-integrated positive electrode may not contain a separate organic and/or inorganic binder. That is, the current collector-integrated positive electrode may be purely composed of a positive electrode active material and a current collector. This means that the battery according to an embodiment of the present invention is free from a decrease in the electrochemical reaction surface area, a decrease in thermal and electrochemical stability, and a decrease in the mass of the active material per unit volume due to the binder.

In addition, as described above, since the current collector-integrated positive electrode is a sintered body having an internal current collector, the positive electrode active material and the current collector and the positive electrode active material may be in a bonded state while forming an interface with each other. That is, there is no point contact or non-uniform surface contact between the positive electrode active material and the positive electrode active material and the current collector, and the positive electrode active material makes stable and homogeneous two-dimensional surface contact with the neighboring positive electrode active material or current collector, and is physically bound to each other. state may be

Due to such interfacial bonding, the current collector-integrated positive electrode may have low contact resistance between the positive electrode active material and the positive electrode active material and the current collector. Furthermore, even though the volume change of the active material generated during the charging/discharging reaction of the battery is repeated, electrical and physical contact between the current collector and the positive electrode active material may be stably maintained.

In addition, since the positive electrode active materials are bound to each other, it is possible to prevent the positive electrode active material from being detached from the positive electrode, and thus, it is possible to prevent the battery capacity from being reduced even during repeated driving for a long time.

The current collector integrated positive electrode has a structure in which one end of the current collector is located inside the sintered body and the other end protrudes outside the sintered body, or the current collector penetrates the sintered body and both ends of the current collector protrude outside the sintered body. can have

1 is a view showing a perspective view in one transmission of a current collector-integrated positive electrode 1000 in a secondary battery according to an embodiment of the present invention. 1 , the current collector-integrated positive electrode 1000 is a sintered body 1100 in which a positive electrode active material is molded and sintered into a predetermined shape, and the current collector 1200 may be positioned inside the sintered body.

In the example of FIG. 1 ( a ), an example in which the shape of the sintered body is a columnar shape is illustrated, but according to the structure of the designed battery, as shown in FIGS. 1 ( b ) to 1 ( c ), the shape of the positive electrode The shape of the sintered body corresponding to may have various shapes, such as a plate shape or a hollow column shape. In the case of a columnar or hollow columnar shape, the cross-sectional shape may have various shapes such as circle, ellipse, triangle, square, pentagon, hexagon, or octagon, but a columnar or hollow columnar shape with good space filling is the most Of course, it can be easy.

An example of FIG. 1 is an example in which one end of the current collector 1200 is positioned inside the sintered body 1100 and the other end of the current collector 1200 protrudes to the outside of the sintered body 1100 .

That is, in the current collector integrated positive electrode 1000 , the current collector 1200 is located inside the sintered body 1100 , but one end of the current collector 1200 is located inside the sintered body 1100 , and the other end of the current collector 1200 is located inside the sintered body 1100 . The stage may be in a state protruding to the outside of the sintered body 1100 . The other end of the current collector 1200 protruding to the outside of the sintered body 1100 may itself serve as a conductor and/or a terminal for electrical connection with the outside of the battery. Alternatively, the other end of the current collector 1200 protruding to the outside of the sintered body 1100 may be connected to a conductive member (not shown) for electrical connection to the outside of the battery.

However, as shown in FIG. 2 , the current collector 1200 may penetrate the sintered body 1100 so that both ends protrude to the outside of the sintered body 1100 . When the current collector 1200 passes through the sintered body 1100, both ends of the current collector 1200 protruding to the outside of the sintered body 1100 serve as a conductor and/or a terminal for electrical connection with the outside of the battery. can Alternatively, both ends of the current collector 1200 protruding to the outside of the sintered body 1100 may be connected to a conductive member (not shown) for electrical connection to the outside of the battery. In the example shown in FIG. 2, the size of the designed positive electrode is large, and thus it is suitable to minimize the increase in resistance due to the resistance of the current collector itself.

The secondary battery according to an embodiment of the present invention may increase the contact area between the current collector and the positive electrode active material only by increasing the volume and/or area of the current collector positioned inside the sintered body. Depending on the use of the battery, the positive electrode typically has a pre-designed size and shape. In a positive electrode having a predetermined size and shape, by using a physically deformed current collector, the volume and/or area of the current collector positioned inside the sintered body may be increased.

Specifically, as shown in the example shown in Fig. 3 (a), the current collector 1200 impregnated in the sintered body 1100 may be in a wrinkled state. That is, the current collector 1200 may have wrinkles 1210 formed in at least an area located inside the sintered body 1100 . Although not particularly limited, the corrugations 1210 formed on the current collector 1200 are in the thickness direction when the sintered body is plate-shaped, and in the case of a hollow columnar or columnar shape, in a direction perpendicular to the height direction of the column, the peaks and valleys of the corrugations are may be formed. 3 is a case in which the sintered body 1100 is of a columnar shape, and when the current collector 1200 is wrinkled 1210 along the height direction of the column, that is, the peaks and valleys of the corrugations are formed in the direction perpendicular to the height direction. is an example showing In consideration of the overall size or shape of the sintered body, the wrinkle width, which is the distance between the valleys (L) and the peaks (H) of the corrugation 1210, or the corrugation distance, which is the distance between the valleys and the valleys (or mountains and mountains), the current collector ( 1200) and the positive electrode active material as long as possible, while increasing the amount of contact between the positive electrode active material and the positive electrode active material as long as it is within a range in which a decrease in battery performance does not occur due to a decrease in the mass of the positive electrode active material per unit volume.

Specifically, as shown in the example shown in FIG. 3B , the current collector 1200 recessed in the sintered body 1100 may have a helical structure. That is, the current collector 1200 may have a spiral structure at least in a region positioned inside the sintered body 1100 . Such a spiral structure is more suitable for a columnar or hollow columnar sintered body. The rotational center of the spiral may coincide with the height direction central axis of the column when the sintered body is columnar or hollow columnar.

An example of FIGS. 1 to 3 shows an example in which a single current collector 1200 is positioned in the sintered body 1100 , but the secondary battery according to an embodiment of the present invention includes two or more current collectors 1200 . It may be located inside the sintered body 1100 .

4 is a view illustrating an example in which two or more current collectors 1200 having a rod shape are positioned inside the sintered body 1100 . 4 , in one sintered body 1100 , two or more current collectors 1200 may be spaced apart from each other and positioned inside the sintered body 1100 . When two or more current collectors 1200 are located, even if the size of the positive electrode is large or the shape of the positive electrode is not simple, uniform and homogeneous charge transfer within the sintered body can be ensured. When the current collector-integrated positive electrode includes two or more current collectors arranged to be spaced apart from each other, the two or more current collectors may each independently have one end or both ends protrude to the outside of the sintered body. Also, it goes without saying that the respective ends of the current collectors protruding to the same side may be electrically connected to each other using a common bonding method such as welding.

In the sodium secondary battery according to an embodiment of the present invention, the current collector is a conductive material foam (foam), foil (film), mesh (mesh), felt (felt), porous foil (perforated film), film (film) ), rods and wires may be selected from one or more. When the conductive material has a highly anisotropic shape such as a wire, tube, or plate, the current collector may include a network of conductive materials. The conductive material may have a specific resistance of 10 ^-9 to 10 ^-3 Ω·m based on 295K. As a non-limiting example, the conductive material may include graphite, graphene, titanium, copper, platinum, aluminum, nickel, silver, gold, or conductive carbon that has excellent conductivity and is chemically stable during charging and discharging of the battery. In this case, the conductive material may be a composite in which different conductive materials are coated or laminated.

The specific structure or shape of the current collector integrated positive electrode described above based on the example of FIGS. 1 to 4 may be appropriately selected and changed according to the structure of the designed battery.

As an example, when the designed battery is a flat-panel battery, a plate-type current collector integrated positive electrode may be used, and when the designed battery is a non-flat-type battery (eg, a tubular battery), based on FIGS. 1 to 4 The above-described columnar or hollow columnar current collector-integrated positive electrode may be used.

More specifically, in the case of a tubular battery, in which the positive electrode is positioned at the center of the tube structure and the negative electrode is located outside the tube structure, a columnar current collector integrated positive electrode may be used. In a tubular battery, when the positive electrode is located adjacent to the outside of the tube structure, that is, in contact with the battery case, and the negative electrode is located in the center of the tube structure, a hollow columnar current collector integrated positive electrode may be used.

A sodium secondary battery according to an embodiment of the present invention includes a negative electrode containing sodium; The current collector integrated positive electrode, the positive electrode to which the positive electrode is charged, and a sodium ion conductive solid electrolyte for separating the negative electrode and the positive electrode are included. That is, the sodium secondary battery according to an embodiment of the present invention is a sodium ion conductive solid electrolyte that separates the anode space from the cathode space, a cathode positioned in the cathode space and containing sodium, and an anolyte solution and an anolyte solution positioned in the anode space. It includes an impregnated current collector integrated positive electrode.

In the secondary battery according to an embodiment of the present invention, the negative electrode may include a negative electrode active material containing sodium, and the negative electrode active material may include sodium metal or a sodium alloy. As a non-limiting example, the sodium alloy may be sodium and cesium, sodium and rubidium, or a mixture thereof. The negative electrode active material may be in a liquid phase including a solid phase or a molten phase at the operating temperature of the battery. As is known, in order to realize a battery capacity of 50 Wh/kg or more, the anode active material may be molten sodium, and the operating temperature of the battery may be 98° C. or higher, which is the melting point of sodium. In this case, of course, the negative electrode may further include a negative electrode current collector for collecting current in contact with the negative electrode active material containing sodium and providing an external and current movement path. When the negative electrode includes molten sodium, the negative electrode current collector may be impregnated with the molten sodium.

In the secondary battery according to an embodiment of the present invention, the positive electrode active material includes a positive electrode active metal, which is at least one metal selected from a transition metal and a group 12 to 14 metal; Or a halide of the positive electrode active metal; may contain. Specifically, the transition metal includes titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu), 12 The Group 14 metal may include zinc (Zn), aluminum (Al), cadmium (Cd), and tin (Sn). That is, the positive electrode active metal is titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn) , one or two or more may be selected from aluminum (Al), cadmium (Cd) and tin (Sn).

The halide of the positive electrode active metal may mean a halide of one or more metals selected from transition metals and Groups 12 to 14 metals. That is, titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), aluminum (Al) ), cadmium (Cd), and tin (Sn) may mean a halide of a positive electrode active metal, which is one or two or more selected metals. In this case, the halide may include iodide, bromide, chloride and/or fluoride.

In the sodium secondary battery according to an embodiment of the present invention, the cathode active material may further contain sodium halide. Sodium halides may include iodides, bromides, chlorides and/or fluorides.

As described above, the positive electrode active material is a positive electrode active metal; halides of positive electrode active metals; Halide of a positive electrode active metal and a positive electrode active metal; positive electrode active metal and sodium halide; halides and sodium halides of positive electrode active metals; The cathode active metal may contain halides and sodium halides of the cathode active metal, and the materials of the cathode active material may be more clearly understood when considering the charge/discharge reaction of a battery to be described later.

In the sodium secondary battery according to an embodiment of the present invention, the sodium ion conductive solid electrolyte provided between the positive electrode (and anolyte) and the negative electrode physically separates the positive electrode (and anolyte) and the negative electrode and is selective for sodium ions Any material having electrical conductivity may be sufficient, and a solid electrolyte commonly used in the battery field for selective conduction of sodium ions is sufficient. As a non-limiting example, the solid electrolyte may be a sodium super ionic conductor (NaSICON), β-alumina, or β"-alumina. As a non-limiting example, the sodium superionic conductor (NASICON) may be Na- Zr-Si-O composite oxide, Na-Zr-Si-PO composite oxide, Y-doped Na-Zr-Si-PO composite oxide, Fe-doped Na-Zr-Si-PO composite oxides or mixtures thereof, specifically, Na ₃ Zr ₂ Si ₂ PO ₁₂ , Na _1+x Si _x Zr ₂ P _3-x O ₁₂ (real number of 1.6<x<2.4), Y or Fe Ga-doped Na ₃ Zr ₂ Si ₂ PO ₁₂ , Y or Fe doped Na _1+x Si _x Zr ₂ P _3-x O ₁₂ (real number of 1.6<x<2.4) or mixtures thereof.

In the sodium secondary battery according to an embodiment of the present invention, based on the shape of the solid electrolyte partitioning the anode space and the anode space by separating the cathode and the anode, the sodium secondary battery is a flat plate comprising a solid electrolyte in a flat plate shape. It may have a battery-type battery structure or a tubular battery structure including a tube-shaped solid electrolyte with one end sealed.

In the secondary battery according to an embodiment of the present invention, the anolyte may be a solution in which sodium salt is dissolved in an organic solvent. Specifically, the sodium salt, which is the solute of the anolyte, has the formula NaY (Y is a monovalent anion, ClO ₄ ^- , PF ₆ ^- , BF ₄ ^- , CF ₃ SO ₃ ^- , AlCl ₄ ^- , AlBr ₄ ^- , AlI ₄ ^- And N(CF ₃ SO ₂ ) ₂ ^{- It} may be one or more materials selected from materials satisfying one or more selected from).

Preferably, the sodium salt contained in the anolyte may be NaAlY ₄ (Y is Cl, Br or I). Thereby, more stable and faster sodium ion conduction can be achieved in a low-temperature operation of 200°C or less, for example, a low-temperature operation of 100 to 200°C.

When the anolyte is a solution in which sodium salt is dissolved in an organic solvent, if the content of sodium salt in the anolyte is too low, there is a risk of a decrease in the charge/discharge rate due to insufficient amount to participate in the electrochemical reaction, and per unit volume of the battery as a whole There is a risk that the energy capacity will be reduced, and there is a risk that the resistance value will increase due to the low ionic conductivity in the solution. If the content of sodium salt in the anolyte is too high, there is a risk that the sodium ion conductivity by the precipitate will be reduced. Accordingly, the anolyte may contain 5 to 30% by weight of sodium salt.

When the anolyte is a solution in which sodium salt is dissolved in an organic solvent, the organic solvent can dissolve the sodium salt, is chemically safe under battery operation (charge/discharge) conditions, and can stably maintain sodium ion conductivity for a long period of time. Any solvent can be used. As a specific example, the organic solvent may be one or more selected from alcohol-based, polyhydric alcohol-based, heterocyclic hydrocarbon-based, amide-based, ester-based, ether-based, lactone-based, carbonate-based, phosphate-based, sulfone-based and sulfoxide-based solvents. . As a non-limiting example, the organic solvent is 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, 5-pentanediol, 2,2-dimethylpropane-1,3-diol, 2-butyl-2-ethylpropane-1,3-diol, 1,5-hexanediol, 1,6-hexanediol, 1,8 -octanediol, 1,10-decanediol, 1,12-dodecanediol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, 1,3-cyclopentanediol, 1,2- Cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4 -Cyclohexanediethanol, glycerol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, formamide, N,N -Dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethyltrifluoroacetamide, hexamethylphosphoramide, acetonitrile, propionitrile, buty Ronitrile, α-terpineol, β-terpineol, dihydroterpineol, N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide, pyrrolidine , Pyrroline, Pyrrole, 2H-Pyrrole, 3H-Pyrrole, 3H-Pyrrole, Pyrazolidine, Imidazolidine, 2-Pyrazoline ( 2-Pyrazoline), 2-imidazoline, 1H-imidazole (1HImidazole), triazole, isoxazole, oxazole, thiazole, iso Thiazole (Isothiazole), Oxadiazole (Oxadiazole), Oxatriazole (Oxatriazole), Dioxazole (Dioxazole), Oxazolone (Oxazolon) e), oxathiazole, imidazoline-2-thione, thiadiazole, triazole, piperidine, pyridine, Pyridazine, Pyrimidine, Pyrazine, Piperazine, Triazine, Morpholine, Thiomorpholine, Indole, Isoindole ( Isoindole), Indazole, Benzisoxazole, Benzoxazole, Benzothiazole, Quinoline, Isoquinoline, Cinnoline, Quinazoline Quinazoline), Quinoxaline, Naphthyridine, Phthalazine, Benzoxazine, Benzoadiazine, Pterdine, Phenazine, Phenothi Phenothiazine, Phenoxazine, Acridine, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, di(2,2,2-trifluoroethyl) carbonate, dipropyl carbonate, dibutyl carbonate, ethylmethyl carbonate, 2, 2,2-trifluoroethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 2,2,2-trifluoroethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate Mate, dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylp Rophyll ether, ethylpropyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methylpropionate, ethyl propionate, propyl propionate, butyl propionate, methylbutyrate ( methyl butyrate), ethyl butyrate, propyl butyrate, butyl butyrate, γ-butyrolactone, 2-methyl-γ-butyrolactone, 3-methyl-γ-butyrolactone, 4-methyl-γ- Butyrolactone, γ-thiobutyrolactone, γ-ethyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, σ-valerolactone, γ- Caprolactone (γ-caprolactone), ε-caprolactone, β-propiolactone (β-propiolactone), tetrahydrofuran (tetrahydrofuran), 2-methyl tetrahydrofuran, 3-methyltetrahydrofuran, trimethyl phosphate (trimethyl phosphate) ), triethyl phosphate, tris (2-chloroethyl) phosphate, tris (2,2,2-trifluoroethyl) phosphate, tripropyl phosphate, triisopropyl phosphate, tributyl phosphate, trihexyl phosphate, triphenyl phosphate , tritolyl phosphate, methyl ethylene phosphate, ethyl ethylene phosphate, dimethyl sulfone, ethyl methyl sulfone, methyl trifluoromethyl sulfone, ethyl trifluoromethyl sulfone, methyl pentafluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di(trifluoromethyl)sulfone, di(pentafluoroethyl)sulfone, trifluoromethylpentafluoroethylsulfone, trifluoromethylnonafluorobutylsulfone, pentafluoroethylnonafluorobutylsulfone, and a solvent selected from the group consisting of sulfolane, 3-methylsulfolane, 2-methylsulfolane, 3-ethylsulfolane and 2-ethylsulfolane.

In the sodium secondary battery according to an embodiment of the present invention, the anolyte may be a molten phase of a sodium salt according to Chemical Formula 1 below.

(Formula 1)

NaM(X ₁ ) _n (X ₂ ) _4-n

In Formula 1, M is an element selected from the group of metals and metalloids having a trivalent oxidation number, X ₁ and X ₂ are different halogen elements, and n is a real number with 0≤n≤4. In this case, the halogen element may include Cl, Br, and I.

Specifically, in the sodium secondary battery according to an embodiment of the present invention, the anolyte may be a molten phase of a sodium salt according to the following Chemical Formula 1-1 or a molten phase of a complex sodium salt according to the following Chemical Formula 1-2.

Formula (1-1)

NaMX ₄

In Formula 1-1, M is the same as defined in Formula 1, and X is a halogen element. That is, Formula 1-1 is a specific chemical formula when n is 0 or 4 in Formula 2, M is an element selected from the group of metals and metalloids having a trivalent oxidation number, and X is Cl, Br, or I.

Formula (1-2)

NaM(X ₁ ) _n (X ₂ ) _4-n

In Formula 1-2, M, X ₁ and X ₂ are the same as defined in Formula 2, and n is a real number such that 0<n<4. That is, Formula 1-2 is a specific chemical formula in the case of a complex sodium salt containing two or more different halogen elements in Formula 1, wherein M is an element selected from the group of metals and metalloids having a trivalent oxidation number, and X ₁ and X ₂ is a halogen element different from each other.

When the anolyte is a molten salt of a sodium salt satisfying Formula 1, specifically Formula 1-1 or Formula 1-2, an organic solvent may not be included as a component of the anolyte, so sodium ion conduction of the anolyte is It can be secured stably for a long period of time, and when manufacturing a battery, raw materials in a solid state are used, so manufacturing and sealing of the battery are easy.

Furthermore, when the anolyte is a molten salt of a complex sodium salt that satisfies Formula 1-2, the melting point is very low without lowering the ionic conductivity of sodium ions, so it is very suitable for low-temperature operation and can have stable sodium ion conductivity. have.

Specifically, in order to have a pair constituting a molten salt electrolyte having a melting point of a certain level or less, X ₁ -X ₂ which are different halogen elements, X ₁ is chlorine (Cl), and X ₂ is iodine (I). Alternatively, X ₁ may be chlorine (Cl) and X ₂ may be bromine (Br). In order to lower the melting temperature of the sodium salt satisfying Formula 1-2 to 150° C. or less, when X ₁ is chlorine (Cl) and X ₂ is iodine (I), n may be 2.0≤n≤3.8, and X _{When 1} is chlorine (Cl) and X ₂ is bromine (Br), n may be 0.2≤n≤3.8. In this case, the cell may have an extremely low operating temperature of 98 to 150°C, specifically 100°C to 150°C, more specifically 120°C to 150°C.

In Formula 1, M may be an element selected from the group of metals and metalloids having a trivalent oxidation number, and specifically may be selected from boron, aluminum, gallium, and indium.

In the secondary battery according to an embodiment of the present invention, the anolyte capable of conducting sodium ions may further include any suitable additives other than the sodium salt described above for the battery to function as intended.

The secondary battery according to an embodiment of the present invention may be charged according to the following Reaction Formula 1 and discharged according to the following Reaction Formula 2.

(Scheme 1)

mNaX+M _act → mNa+M _act X _m

In Scheme 1, NaX is sodium halide, M _act is a positive electrode active metal, and m is a natural number of 1 to 4.

(Scheme 2)

mNa+M _act X _m → mNaX+M _act

In Scheme 2, M _act is a positive electrode active metal, M _act X is a halide of a positive electrode active metal, and m is a natural number of 1 to 4.

In detail, in Schemes 1 and 2, m may be a natural number corresponding to the positive valence of the metal (M).

As shown in Schemes 1 and 2, the electrochemical (charge/discharge) reaction of the battery is sodium; a positive electrode active metal which is at least one metal selected from transition metals and Groups 12 to 14 metals; and halogen; sodium may be derived from the negative electrode and/or positive electrode active material, and the positive electrode active metal and halogen may be derived from the positive electrode active material.

In detail, in the sodium secondary battery according to an embodiment of the present invention, based on the state of charge of the battery by the charging reaction according to Scheme 1, the sintered body of the positive electrode may include a halide of a positive electrode active metal; Or a halide of the positive electrode active metal and the residual positive electrode active metal; may include. Based on the discharge state of the battery by the discharge reaction according to Scheme 2, the sintered body of the positive electrode includes a positive electrode active metal and a sodium halide; or a halide of the remaining positive electrode active metal together with the positive electrode active metal and sodium halide; may include.

As described above, in the secondary battery according to an embodiment of the present invention, sodium; positive electrode active metal; and halogen; as it is involved, the current collector of the current collector-integrated positive electrode may be the same metal as the positive electrode active metal. Through this, the current collector provided in the current collector-integrated positive electrode may serve as an active material participating in the battery reaction as well as a normal current collector role of movement and supply of current and electrical connection to the outside.

In the manufacturing method, the current collector-integrated positive electrode is a mold having an empty space in the form of a positive electrode to be manufactured, a current collector is charged into the mold so that one end of the current collector is located in the mold inner space, and then the positive electrode active material is placed in the mold After filling the inner space of the mold by inputting an electrode material containing

In the case of manufacturing a current collector-integrated positive electrode having a structure in which both ends of the current collector protrude, the current collector-integrated positive electrode has an empty space in the form of a positive electrode to be manufactured and has a groove (penetrating) having the same shape as that of one end of the current collector. After placing one end of the current collector in the groove of the mold using a mold having a mold groove), fill the empty space in the mold with an electrode material, press-molding, and remove the mold to prepare a molded body , may be prepared including the step of heat-treating the molded body. As described above, the electrode material input to the mold may not contain a separate binder.

At this time, when the mechanical strength of the current collector is relatively high, such as a rod-type current collector, after a molded body is manufactured using only the electrode material, the current collector is physically inserted into the molded body and then heat-treated to manufacture an integrated current collector positive electrode. In this case, it is more economical to use the same mold even if the shape or position of the current collector is changed.

The pressure applied to the mold (pressure during molding) or the heat treatment temperature may be appropriately adjusted within a range in which the sintered body may have a porosity of 50 to 75%. However, in order to prevent excessive densification and achieve strong interfacial bonding between the positive electrode active material and the positive electrode active material and the current collector, the heat treatment may be performed at 500 to 700 °C, specifically 600 to 650 °C. The heat treatment may be performed in an inert atmosphere or a reducing atmosphere, the inert atmosphere may be nitrogen, argon, helium, or the like, and the reducing atmosphere may be a hydrogen atmosphere. In this case, the hydrogen atmosphere may include a mixed gas atmosphere of hydrogen and an inert gas. Under the above-described heat treatment conditions, the pressure applied during molding may be appropriately adjusted to a pressure within a range capable of having the above-described porosity.

FIG. 5 is a diagram illustrating a structure of a sodium secondary battery according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating an example in which an anode is positioned at the center of a tube structure in a secondary battery having a tube structure. 5 , the sodium secondary battery according to an embodiment of the present invention has a cylindrical metal housing 100 with a closed bottom and an open top, located inside the metal housing 100 , and the metal housing 100 ) of a tube-shaped solid electrolyte (hereinafter referred to as a solid electrolyte tube, 300), a safety tube (safety tube, 410) and a wicking tube (wicking tube, 420), which are sequentially positioned from the outside to the inside and have a sealed tube shape. .

In detail, the innermost, that is, the wicking tube 420 located in the center of the metal housing 100 may have a tube shape with a through hole 1 formed at the bottom, and the safety tube 410 is the wicking tube 420 outside. It may have a structure that surrounds the wicking tube 420 while having a predetermined separation distance.

The negative electrode 400 containing molten sodium is provided inside the wicking tube 420 , and an empty space between the wicking tube 420 and the safety tube 410 through the through hole 1 formed in the lower portion of the wicking tube 420 . has a structure that fills The double structure of the wicking tube 420 and the safety tube 410 prevents a violent reaction between the anode material and the cathode material when the solid electrolyte tube 300 is broken, and keeps the level of molten sodium constant even during discharge by capillary force. structure that can be maintained.

The solid electrolyte tube 300 is positioned to surround the safety tube 410 on the outside of the safety tube 410 and may be a tube-shaped solid electrolyte having selective permeability to ^{sodium ions (Na + ).}

In the space between the solid electrolyte tube 300 and the metal housing 100 surrounding the safety tube 410, the anolyte 220 and the anolyte 220 that can conduct sodium ions to and from the solid electrolyte tube A locked current collector integrated positive electrode 1000 may be provided.

That is, the sodium secondary battery according to an embodiment of the present invention has a concentric structure, and the wicking tube 420, the safety tube 410, the solid electrolyte tube 300 and the metal housing 100 are sequentially positioned from the inside to the outside. The negative electrode 400 containing molten sodium is supported in the wicking tube 420, and the anolyte 220 and the anolyte solution in the space between the solid electrolyte tube 300 and the metal housing 100 ( The current collector integrated positive electrode 1000 may be provided to be impregnated in 220 . At this time, although not shown separately in the drawings, the current collector protruding from the current collector-integrated positive electrode 1000 may be electrically connected to the outside and connected to a conductive member serving as a terminal, and specifically, the current collector-integrated positive electrode ( Of course, the current collector protruding from 1000) may be connected to the metal housing 100 .

Furthermore, the sodium battery according to an embodiment of the present invention has a cover 110 and a ring shape positioned on the metal housing 100 to seal the inside of the metal housing, and is positioned on the metal housing 100 to the top of the metal housing 100 . ) and the solid electrolyte tube 300 may further include an insulator 120 electrically insulated and an electrode terminal 130 positioned around the upper end of the metal housing 100 . In addition, in order to minimize evaporation of the liquid phase, the pressure inside the cell sealed by the cover 110 immediately after manufacturing may be 15 psi or more. In addition, it goes without saying that the negative electrode current collector may be introduced through the through hole of the cover 110 so that a certain area is impregnated with the molten sodium negative electrode supported inside the wicking tube 420 .

As described above, the present invention has been described with specific details and limited examples and drawings, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is not limited to the above embodiments. Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (15)

a cathode containing sodium;
a current collector integrated positive electrode, which is a sintered body of a positive electrode active material having a current collector embedded therein;
an anolyte in which the positive electrode is charged; and
a sodium ion conductive solid electrolyte separating the anode and the anolyte;
A sodium secondary battery comprising a. The method of claim 1,
The current collector is one of a foam, a film, a mesh, a felt, a perforated film, a film, a rod and a wire of a conductive material A sodium secondary battery selected above. The method of claim 1,
At least one end of the current collector protrudes outside the sintered body and is connected to a conductive member for electrical connection with the outside of the battery. 4. The method of claim 3,
The current collector embedded in the sintered body is a corrugated sodium secondary battery. 4. The method of claim 3,
The current collector embedded in the sintered body is a sodium secondary battery having a helical structure. The method of claim 1,
The sintered body is a columnar or hollow columnar sodium secondary battery. The method of claim 1,
A sodium secondary battery in which two or more current collectors are arranged to be spaced apart from each other in the sintered body. The method of claim 1,
A sodium secondary battery having a porosity of 50 to 75% of the sintered body. 9. The method according to any one of claims 1 to 8,
The cathode active material may include a cathode active metal, which is at least one metal selected from transition metals and Groups 12 to 14 metals; Or a halide of the positive electrode active metal; sodium secondary battery containing. 10. The method of claim 9,
The cathode active material is a sodium secondary battery further containing sodium halide. 10. The method of claim 9,
The anolyte is a sodium secondary battery containing a sodium salt satisfying the following formula (1).
(Formula 1)
NaM(X ₁ ) _n (X ₂ ) _4-n
(In Formula 1, M is an element selected from the group of metals and metalloids having a trivalent oxidation number, X ₁ and X ₂ are different halogen elements, n is a real number with 0≤n≤4) 12. The method of claim 11,
Wherein X ₁ and X ₂ are chlorine (Cl) and iodine (I), n is 2.0 to 3.8 sodium secondary battery. 12. The method of claim 11,
Wherein X ₁ and X ₂ are chlorine (Cl) and bromine (Br), n is 0.2 to 3.8 sodium secondary battery. 10. The method of claim 9,
The positive electrode active metal is titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), One or two or more sodium secondary batteries selected from aluminum (Al), cadmium (Cd) and tin (Sn). 11. The method of claim 10,
A sodium secondary battery comprising charging according to Scheme 1 and discharging according to Scheme 2 below.
(Scheme 1)
mNaX+M _act → mNa+M _act X _m
(In Scheme 1, NaX is sodium halide, M _act is a positive electrode active metal, and m is a natural number of 1 to 4)
(Scheme 2)
mNa+M _act X _m → mNaX+M _act
(In Scheme 2, M _act is a positive electrode active metal, M _act X is a halide of a positive electrode active metal, and m is a natural number of 1 to 4)

Images