KR101914171B1 - Negative electrode for sodium secondary battery, and sodium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a negative electrode for a sodium secondary battery and a sodium secondary battery including the same. By including the negative electrode active material in at least one surface of the porous collector including a plurality of pores and the negative electrode active material, the current density per unit area can be reduced by uniformizing the electron distribution in the electrode and increasing the surface area of the electrode, The growth can be suppressed and shorting of the battery can be prevented.

Description

TECHNICAL FIELD [0001] The present invention relates to a negative electrode for a porous sodium secondary battery, and a sodium secondary battery including the negative electrode. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a negative electrode for a sodium secondary battery and a sodium secondary battery including the negative electrode. More particularly, the present invention can reduce the current density per unit area by uniformizing the electron distribution in the electrode and increasing the surface area of the electrode, To a sodium secondary battery and a sodium secondary battery including the same.

BACKGROUND ART [0002] In recent years, secondary batteries have been used in a wide range of applications, ranging from large capacity batteries for power storage, mid-sized batteries for transportation, and small batteries used as power sources for portable devices. have. Among such secondary batteries, lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate are commercially available and widely used. However, since a lithium secondary battery uses a large amount of rare metals such as cobalt, nickel, and lithium, there is a concern about supply of the rare metal due to an increase in demand for a large secondary battery.

On the other hand, interest is focused on the next-generation sodium secondary battery, which is richly buried in an even distribution throughout the world with an alkali metal belonging to Group 1 of the periodic table together with lithium and has an oxidation-reduction potential value equal to that of lithium and a high energy density .

The sodium secondary battery is composed of a positive electrode containing a positive electrode active material capable of doping and dedoping sodium ions, a negative electrode containing a negative electrode active material capable of doping and dedoping sodium ions, and a nonaqueous electrolyte containing sodium ions , As in the lithium ion of the lithium secondary battery, the sodium ion reciprocates between the negative electrode and the positive electrode through the electrolyte, thereby charging and discharging the battery. A state in which sodium ions are occluded (doped) in a negative electrode active material corresponds to charging, and a state in which sodium ions are desorbed (de-doped) from a negative electrode active material corresponds to a discharge.

However, the sodium ion is larger in size than the lithium ion, so that the diffusion rate is slow and the reaction activity is also very low. Due to the nature of such sodium ions, the materials available for the anode of sodium secondary batteries are limited. Specifically, an active material usable for an electrode for a sodium secondary battery should have a small primary particle size and a high diffusion rate. In addition, when an electrode material used in a lithium secondary battery is applied to a sodium secondary battery, the capacity is often not exhibited, or abrupt degradation in capacity and deterioration in characteristics are caused as compared with characteristics exhibited in a lithium secondary battery.

The anode materials of the sodium secondary batteries studied up to now are mainly carbon-based materials, transition metal oxides, metal sodium or its alloys, and phosphates. Among them, the negative electrode using metal sodium has a large capacity density. However, there is a problem that dendrite of sodium grows due to repetition of charging and discharging, and the separator is destroyed, resulting in a short circuit of the electrode phase. In this case, the charge / discharge cycle efficiency is rapidly lowered and the safety of the battery is lowered. In order to solve this problem, a method of operating the battery at a temperature lower than the melting point of sodium was proposed. In this case, since the sodium starts to soften as the temperature rises, it causes deformation of the sodium cathode, There is a problem that the charge-discharge cycle efficiency (capacity retention rate) and cycle characteristics are deteriorated.

1) Japanese Patent Registration No. 2916023 (registered on April 16, 1999)

It is an object of the present invention to provide a sodium secondary battery which can reduce the current density per unit area by uniforming the distribution of electrons in the electrode and increase the surface area of the electrode and can prevent short circuit of the battery by suppressing growth of dendrite Thereby providing a cathode.

Another object of the present invention is to provide an electrode assembly including the negative electrode and a sodium secondary battery.

According to an embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: a porous current collector including a plurality of pores; and a negative electrode active material positioned in the pores of the porous current collector, wherein the negative electrode active material is selected from the group consisting of metal sodium and sodium alloys A negative electrode for a sodium secondary battery comprising one or a mixture of two or more of them.

The negative electrode for a sodium secondary battery according to claim 1, wherein the porous current collector has a three-dimensional network structure in which the plurality of pores are connected to each other, the negative electrode active material is located in the three-dimensional mesh pore structure, A three-dimensional network structure can be formed.

In the negative electrode for a sodium secondary battery, the porosity of the porous collector may be 50 to 99% by volume, and the average diameter of the pores may be 5 to 500 탆.

In the negative electrode for a sodium secondary battery, the porous collector may be made of at least one selected from the group consisting of Cu, Ni, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, , Bi, Si, Sb, an alloy thereof, and a carbon-based material.

In the negative electrode for a sodium secondary battery, the sodium alloy may be any one selected from the group consisting of Al, Sn, Bi, Si, Sb, B, and alloys thereof, and an alloy of sodium and sodium.

In the negative electrode for a sodium secondary battery, at least one of Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Al, Sn, Bi, Si, Sb, and alloys thereof.

In the negative electrode for a sodium secondary battery, a binder may be further included in the pores of the porous current collector.

The negative electrode for a sodium secondary battery may further include a negative electrode active material layer disposed on at least one side of the porous current collector.

The negative electrode active material may be included in an amount of 5 to 50% by weight based on the total weight of the negative electrode for a sodium secondary battery.

In addition, the negative electrode for a sodium secondary battery includes a protective layer disposed on the porous current collector, and the protective layer may include a sodium ion conductive polymer.

The sodium ion conductive polymer may be at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethylmethacrylate (PMMA), polyethylene oxide (PEO) And a combination thereof.

The protective layer may have a thickness of 0.1 占 퐉 to 20 占 퐉.

According to another embodiment of the present invention, an anode active material capable of sodium insertion and extraction is formed by using at least one method selected from the group consisting of melt infiltration, vapor deposition, electroplating, roll pressing and slurry application , And coating and filling at least one surface of the porous current collector including a plurality of pores and into the pores, wherein the negative electrode active material includes one or a mixture of two or more selected from the group consisting of metal sodium and sodium alloys The present invention also provides a method of manufacturing a negative electrode for a sodium secondary battery as described above.

In addition, the manufacturing method may further include a step of applying the anode active material after the application and filling of the anode active material.

According to another embodiment of the present invention, there is provided an electrode assembly for a sodium secondary battery, wherein the negative electrode and the positive electrode are alternately stacked with a separator as a boundary.

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

The negative electrode for a sodium secondary battery according to the present invention includes the negative electrode active material dispersed in the pores of the porous current collector so that the electrons can be uniformly distributed in the electrode and the electrode surface area can be increased to reduce the current density per unit area , It is possible to suppress the growth of the dendrite and to prevent the battery short circuit.

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.

A negative electrode for a sodium secondary battery according to an embodiment of the present invention includes: a porous collector including a plurality of pores; And a negative electrode active material positioned in the pores of the porous current collector, wherein the negative electrode active material includes one or a mixture of two or more selected from the group consisting of metallic sodium and sodium alloys.

In general, the current collector in the sodium secondary battery serves to collect electrons generated by the electrochemical reaction of the active material or to supply electrons necessary for the electrochemical reaction, as in the lithium secondary battery. Specifically, And supplies the electrons supplied from the anode to the anode active material at the time of charging. Accordingly, it is required to have a high current collecting efficiency and a mechanical strength enough to serve as a support for the electrode.

In the anode for a sodium secondary battery according to an embodiment of the present invention, the porous current collector includes a plurality of pores that can be filled (or impregnated) with a negative electrode active material as well as a function as a general electrode current collector. As a result, the negative electrode active material is included in at least one surface of the porous current collector, that is, at least one external surface, and the pores dispersed in the current collector, so that the electrons in the electrode can be uniformly distributed. Further, the surface area of the electrode is increased, so that the current density per unit area can be reduced, and the growth of the dendrite can be suppressed to prevent the short circuit of the battery.

Furthermore, the plurality of pores included in the porous current collector may be connected to each other to form a three-dimensional network structure. In this case, according to the three-dimensional network structure of the pores, the active material included in the pores also forms a three-dimensional network structure, so that the movement of electrons is facilitated by the formation of a continuous electron transfer path, have.

Considering the function of the current collector as the support in the electrode, the porosity of the porous current collector is specifically 50 to 99% by volume, and the average diameter of the pores May be 5 to 500 mu m. In consideration of the remarkable improvement effect of controlling the average diameter of the pores and the pores, the porosity of the porous collector is more preferably 60 to 80% by volume and the average diameter of the pores is 10 to 100% Mu] m.

The porous collector may be made of a material capable of exhibiting excellent current collecting efficiency without being alloyed with Na, specifically, Cu, Ni, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, A metal such as Ru, Pt, Ir, Al, Sn, Bi, Si, Sb or an alloy thereof; Carbon-based materials such as carbon, graphite or graphene; Or a composite or multilayer laminate of the metal and the carbon-based material. Of these, the porous current collector may more specifically include copper in that it is difficult to form an alloy with sodium and is easily processed into a thin film.

The negative electrode for a sodium secondary battery according to an embodiment of the present invention may further include an active material capable of storing and releasing sodium ions on at least one surface of the porous current collector. As described above, the performance of the battery can be greatly improved by further including an active material on the surface of the collector as well as in the current collector.

On the other hand, in the negative electrode for a sodium secondary battery, the negative electrode active material contained in the pores of the porous current collector may be metal sodium or an alloy thereof. The sodium alloy may be an alloy of any one selected from the group consisting of Al, Sn, Bi, Si, Sb, B and their alloys and sodium.

The negative electrode active material may be a carbon-based material such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbon materials, carbon fibers, sintered organic polymer compounds, amorphous hard carbon and the like capable of storing and releasing sodium ions; Transition metal oxides such as Na ₂ Ti ₃ O, Li ₄ Ti ₅ O ₁₂ and the like; Metal sodium or an alloy thereof; And a phosphate, and optionally a mixture of two or more thereof.

In an anode for a sodium secondary battery according to an embodiment of the present invention, Ni, Cu, Ti, V, Cr, Mn, Fe, and Co are added in the pores of the porous collector in addition to the above- And one or more metals selected from the group consisting of Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Al, Sn, Bi, Si, Sb and alloys thereof.

The metal may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material.

The negative electrode for a sodium secondary battery may further include a binder for increasing the binding force between the active material and the active material and the porous current collector.

The binder is not particularly limited as long as it does not interfere with the electrode reaction and does not interfere with the conduction of sodium ions. Specific examples thereof include polyvinyl alcohol (PVA), carboxymethyl cellulose, hydroxypropylcellulose, Polyethylen oxide (PEO), polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene (PTFE), poly (ethylene terephthalate), polyvinyl chloride, polyvinyl chloride, But are not limited to, vinylidene fluoride, polyolefin styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon. Of these, polytetrafluoroethylene, polyvinyl alcohol, polyethylene, polypropylene, polyethylene oxide, polyvinylidene fluoride, carboxymethylcellulose, or a mixture thereof may be used.

The binder may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the negative electrode active material.

The negative electrode active material may be included in an amount of 5 to 50% by weight, and preferably 10 to 30% by weight based on the total weight of the negative electrode for a sodium secondary battery. At this time, the total weight of the negative electrode for a sodium secondary battery may be the combined weight of the porous collector and the negative electrode active material. If the content of the negative electrode active material is less than 5 wt%, the energy density may be lowered, and if it is more than 50 wt%, the dendrite inhibiting effect may be lowered.

The negative electrode for a sodium secondary battery may further include a protective layer disposed on the porous current collector. The protective layer may be located on one side or both sides of the porous current collector and the negative electrode for a sodium secondary battery may further include an active material capable of storing and releasing sodium ions on at least one surface of the porous current collector as described above And may be located on the surface of the active material located on one side of the porous current collector.

At this time, the protective layer includes a sodium ion conductive polymer. The sodium ion conductive polymer may be at least one selected from the group consisting of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), polyethylene oxide (PEO) The polymer can be ion-exchanged with the polymer since the polymer is swelled into an electrolyte and driven.

In addition, if the thickness of the protective layer is less than 0.1 탆, it may be difficult to block moisture during the process. If the thickness exceeds 20 탆, The output characteristics may be degraded.

The negative electrode for a sodium secondary battery according to an embodiment of the present invention having the above-described structure exhibits a low additive density as a pore-active material of the porous current collector is impregnated or filled. Specifically, the mixture density of the negative electrode may be 0.80 to 1.25 g / cm ³ , more specifically 0.90 to 1.15 g / cm ³ .

In addition, the thickness of the cathode may be 25 to 1300 탆, more specifically 50 to 1000 탆.

The negative electrode for a sodium secondary battery includes: preparing a porous current collector including a plurality of pores; The negative electrode active material capable of intercalating and deintercalating sodium ions is applied to at least one surface and pores of the porous current collector by using at least one method selected from the group consisting of melt infiltration, electroplating, vapor deposition, roll pressing and slurry application. And a filling step. According to another aspect of the present invention, there is provided a method of manufacturing the negative electrode for a sodium secondary battery.

Specifically, in the above production method, step 1 is a step of preparing a porous current collector.

The porous current collector may be manufactured according to a conventional method for producing a porous current collector, except that the porous current collector is performed so as to realize the kind and physical property as described above.

In the above manufacturing method, step 2 may be carried out by using at least one method selected from the group consisting of melt infiltration, electroplating, vapor deposition, and slurry application, .

The melt infiltration, electroplating, vapor deposition, and slurry application may be performed according to a conventional method.

Specifically, the deposition can be performed by a physical vapor deposition method such as a thermal evaporation method, an electron beam evaporation method, an ion beam evaporation method, a sputtering method, an arc evaporation method, and a laser ablation evaporation method.

The slurry may be applied by pasting the active material into a solvent or by mixing the active material with a conductive material, a binder, etc., and then applying the paste to the paste. Examples of the solvent include aprotic polar solvents such as N-methyl-2-pyrrolidone, alcohols such as isopropyl alcohol, ethyl alcohol or methyl alcohol, ethers such as propylene glycol dimethyl ether, acetone, methyl ethyl And ketones such as ketone or methyl isobutyl ketone. Examples of the coating method include a doctor blade method, a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spraying method.

In addition, the manufacturing method may further include a step of filling the negative electrode active material in step 2, followed by pressing, in order to manufacture a high-density electrode.

The squeezing process may be performed by using a squeezing method commonly used in the production of electrodes, and specifically, by performing roll pressing or plate pressing at a pressure of 10 kg / cm ² to 100 ton / cm ² .

By the above-described manufacturing method, the active material penetrates and fills not only the outer surface of the porous current collector but also the pores of the porous current collector, whereby the current density per unit area can be reduced by uniformizing the electron distribution in the electrode and increasing the surface area of the electrode , It is possible to prevent the short circuit of the battery by suppressing the growth of the dendrite, thereby improving the capacity and lifetime characteristics of the battery. In addition, since the electrode current collector is porous, there is no fear that the moving speed of the sodium ion is lowered, and in particular, the effect can be greatly increased in a large-sized battery.

According to another aspect of the present invention, there is provided an electrode assembly for a sodium secondary battery including the negative electrode.

Specifically, the electrode assembly has the positive electrode and the negative electrode alternately stacked with the separator as a boundary, and the negative electrode is as described above.

In the electrode assembly, the positive electrode includes a positive electrode collector and a positive electrode active material layer disposed on at least one surface of the positive electrode collector.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, carbon, nickel, titanium, , Silver or the like may be used. In addition, the cathode current collector may have a thickness of 3 to 500 탆, and fine unevenness may be formed on the surface of the current collector to increase the adhesive force of the cathode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

In addition, the cathode active material layer includes a cathode active material, and optionally, a conductive material and a binder.

As the cathode active material, Na _x CoO ₂ , Na _x Co _2/3 Mn _1/3 O ₂ , Na _x Fe _1/2 Mn _1/2 O ₂ , NaCrO ₂ , NaLi _0.2 Ni _0.25 Mn _0.75 O _2.35 , Sodium metal oxides such as Na _0.44 MnO ₂ , NaMnO ₂ , Na ₂ Fe ₅ Si ₁₂ O ₃₀ , Na _0.7 VO ₂ , or Na _0.33 V ₂ O ₅ (where 0 <x≤1); Oxides such as Na ₃ V ₂ (PO ₄ ) ₃ , NaFePO ₄ , NaMn _0.5 Fe _0.5 PO ₄ , Na ₃ V ₂ (PO ₄ ) ₃ , Na ₃ Fe ₂ (PO ₄ ) ₃ and the like; Na ₂ FePO ₄ F, Na ₃ V ₂ (PO ₄ ) _3, and the like; Sodium or metal fluoride such as sulfur oxides NaFeSO ₄ F; Composite metal oxide of the transition metal _{- NaFeO 2, NaMnO 2, NaNiO} 2 and ₂ NaCoO sodium and the like; Sodium metal fluorides such as Na ₃ FeF ₆ or Na ₂ MnF ₆ ; Sodium metal borates such as NaFeBO ₄ , or Na ₃ Fe ₂ (BO ₄ ) ₃ ; And chalcogen compounds such as TiS ₂ , ZrS ₂ , VS ₂ , V ₂ S ₂ , TaS ₂ , FeS ₂ or NiS _2, and any one or a mixture of two or more of them may be used. Among them, the Fe-containing compound can suppress the elution of the transition metal ions even when the temperature of the electrolyte in the battery is increased, and as a result, the cycle characteristics and the discharge capacity retention rate of the sodium secondary battery can be improved. In addition, chalcogen compounds such as TiS ₂ , ZrS ₂ , and the like can store and desorb sodium ions at a higher potential than the negative electrode when used in combination with metal sodium or its alloy based negative active material, And can exhibit further increased reactivity.

In addition, the binder plays a role of attaching the positive electrode active material particles to each other well and attaching the positive electrode active material to the current collector well. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylcellulose, diacetylcellulose, Polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, Butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black , Ketjen black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

The positive electrode having the above structure can be produced according to a conventional positive electrode manufacturing method, except that the positive electrode active material is used. Specifically, the positive electrode active material layer forming material containing the positive electrode active material, the binder and the conductive material may be coated on the positive electrode current collector, followed by drying and rolling.

Meanwhile, in the electrode assembly, the separation membrane is interposed between the positive electrode and the negative electrode to insulate the positive electrode from the negative electrode, thereby interrupting the internal short circuit of the electrode and impregnating the electrolyte.

As the separation membrane, an insulating thin film having high ion permeability and mechanical strength can be used. The thickness of the separator may be preferably as thin as long as the mechanical strength is maintained because the volume energy density of the battery becomes high and the internal resistance becomes small. Specifically, the separation membrane may have a pore diameter of 0.01 to 10 탆, an air permeability of 50 to 300 sec / 100 cc, and a thickness of 5 to 310 탆.

The separator may be any of those generally used in the art. More specifically, it is possible to use a polymer resin having a chemical resistance and a hydrophobic property, or a glass fiber, and more specifically, a high-density polyethylene, a low density polyethylene, a linear low density polyethylene, a ultra high molecular weight polyethylene, a polypropylene, a polyethylene terephthalate, But are not limited to, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, polyethylenenaphthalene, and copolymers thereof. Any one or a mixture of two or more of them may be used.

The separation membrane may further include a heat-resistant porous layer positioned on at least one side of the separation membrane. The heat-resistant porous layer has excellent heat resistance, thereby blocking an electric current when an abnormal current flows in the battery due to a short circuit between the anode and the cathode or the like, thereby preventing an excessive current from flowing. In addition, It is possible to prevent the waving of the separation membrane.

Specifically, the heat resistant porous layer may be formed of an inorganic powder such as alumina, silica, titanium dioxide or calcium carbonate; Or polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyether ketone, aromatic polyester, polyether sulfone and polyether imide. , Polyamide, polyimide, polyamideimide, polyethersulfone, polyetherimide, and the like. Among them, the polar group contained in the molecule has a good affinity with the non-aqueous electrolyte, so that the liquid electrolyte in the heat-resistant porous layer is highly liquid, the infiltration rate is fast, and the charge / discharge capacity of the sodium secondary battery (Para-oriented aromatic polyamide, meta-oriented aromatic polyamide), an aromatic polyimide, an aromatic polyimide, an aromatic polyimide, an aromatic polyimide, an aromatic polyimide, And nitrogen-containing aromatic polymers such as amide imides. In addition, the nitrogen-containing aromatic polymer may promote the formation of a solid layer on the surface of the anode due to decomposition of the electrolyte, thereby reducing the irreversible capacity of the sodium secondary battery.

When the separator further comprises a heat-resistant porous layer, the heat-resistant porous layer is disposed on the cathode side.

In the present invention, the electrode assembly may have a stacked structure or a stacked / folded structure in which at least one positive electrode and at least one negative electrode are alternately stacked with a separation membrane as a boundary, and are not particularly limited.

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

Specifically, the sodium secondary battery includes the electrode assembly and the electrolyte. At this time, It can be an electrolytic solution or a solid electrolyte which conducts sodium ions quickly and uniformly.

When the electrolyte is an electrolytic solution, it includes an electrolyte salt and a solvent.

Specific examples of the electrolytic salt include sodium hydroxide (for example, sodium hydroxide (NaOH)), borate (for example, sodium metaborate (NaBO ₂ ), borax (Na ₂ B ₄ O ₇ ) (E.g., H ₃ BO ₃ ), phosphates such as trisodium phosphate (Na ₃ PO ₄ ), sodium pyrophosphate (Na ₂ HPO ₄ ), etc.), chloric acid (such as NaClO ₄ ) ₄ , NaAsF ₆ , NaBF ₄ , NaPF ₆ , NaSbF ₆ , NaCF ₃ SO ₃ or NaN (SO ₂ CF ₃ ) ₂ , and any one or a mixture of two or more thereof may be used.

The electrolyte may contain 2 to 50% by weight of the electrolyte salt based on the total weight of the electrolyte.

In addition, the solvent can be used without any particular limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the solvent may be an aqueous solvent such as water, alcohol, or the like; Or a nonaqueous system such as an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, or a carbonate solvent. These may be used singly or in combination of two or more.

Specific examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, But are not limited to, ethyl propionate,? -Butyrolactone, decanolide,? -Valerolactone, mevalonolactone,? -Caprolactone (? -caprolactone, 隆 -valerolactone, 竜 -caprolactone, and the like.

Specific examples of the ether solvent include dibutyl ether, tetraglyme, 2-methyltetrahydrofuran, tetrahydrofuran, and the like.

Specific examples of the ketone-based solvents include cyclohexanone and the like. Specific examples of the aromatic hydrocarbon organic solvent include benzene, fluorobenzene, chlorobenzene, iodobenzene, toluene, fluorotoluene, xylene, (xylene), and the like. Examples of the alkoxyalkane solvent include dimethoxy ethane and diethoxy ethane.

Specific examples of the carbonate solvent include dimethylcarbonate (DMC), diethylcarbonate (DEC), dipropylcarbonate (DPC), methylpropylcarbonate (MPC), ethylpropylcarbonate (EPC) , Methyl ethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylenes carbonate (BC) And fluoroethylene carbonate (FEC).

When the electrolyte is a solid electrolyte, specifically, an organic polymer electrolyte such as a polymer compound containing at least one of a polyethylene oxide-based polymer compound, a polyorganosiloxane chain, and a polyoxyalkylene chain may be used. A so-called gel type in which a non-aqueous electrolyte solution is held in a polymer compound may also be used. In addition, sulfide electrolytes such as Na ₂ S-SiS ₂ and Na ₂ S-GeS ₂ , NaZr ₂ (PO ₄ ) ₃ An inorganic solid electrolyte such as a NASICON-type electrolyte, etc. may be used. When these solid electrolytes are used, there are cases where safety can be further increased.

In the case of using the solid electrolyte in the sodium secondary battery of the present invention, the solid electrolyte may serve as a separator, and in this case, a separator may not be required.

In addition to the above electrolyte components, the electrolyte may further contain an additive (hereinafter, referred to as "other additive") that can be generally used for an electrolyte for the purpose of improving lifetime characteristics of the battery, suppressing reduction in battery capacity, .

It is preferable that 0.1 to 5% by weight of fluorinated ethylene carbonate is further added to the electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. However, the following embodiments are intended to illustrate the invention, but the invention is not limited thereto.

(Example 1)

(1) Preparation of positive electrode

A slurry for a cathode active material was prepared in which NaCoO ₂ as a cathode active material, Super P as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were 95 wt%, 2.5 wt% and 2.5 wt%, respectively, Coated on an aluminum current collector, and then dried to produce a positive electrode.

(2) Manufacture of cathodes

A sodium foil was placed on a current collector of a copper foam having an average pore size of 300 μm and a porosity of 70%, and inserted into the pores of the copper foam through roll pressing to prepare an electrode composite. At this time, the sodium metal was adjusted to be 5% by weight based on the total weight of the electrode composite. Thereafter, a negative electrode was prepared by forming a 5 탆 thick polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP) sodium ion conductive protective film on the electrode composite.

(3) Preparation of sodium secondary battery

An electrode assembly having a polypropylene porous film interposed therebetween was inserted between the prepared positive electrode and negative electrode into a battery case of a pouch type and then a nonaqueous electrolytic solution (1M NaPF ₆ , EC: EMC = 3: 7 ) Was injected, and then a sodium secondary battery was prepared by completely sealing.

(Example 2)

A sodium secondary battery was prepared in the same manner as in Example 1, except that a negative electrode to which an electrode composite containing 10% by weight of sodium metal based on the total weight of the electrode composite was applied was used.

(Example 3)

A sodium secondary battery was prepared in the same manner as in Example 1, except that a negative electrode to which an electrode composite containing 20 wt% of sodium metal based on the total weight of the electrode composite was applied was used as the negative electrode.

(Example 4)

A sodium secondary battery was prepared in the same manner as in Example 1, except that a negative electrode to which an electrode composite containing 30% by weight of sodium metal based on the total weight of the electrode composite was applied was used.

(Example 5)

A sodium secondary battery was prepared in the same manner as in Example 1, except that a negative electrode to which an electrode composite containing 50% by weight of sodium metal based on the total weight of the electrode composite was applied was used.

(Example 6)

A sodium secondary battery was produced in the same manner as in Example 1, except that only the electrode composite in which the sodium ion conductive protective film was not formed was used as the cathode.

(Comparative Example 1)

As a negative electrode, a negative electrode was prepared by sequentially laminating sodium foil and polyvinylidene fluoride-hexafluoro-propane (PVDF-co-HFP) sodium ion conductive protective film having a thickness of 5 탆 on a common plate- A sodium secondary battery was prepared in the same manner as in Example 1. The results are shown in Table 1. &lt; tb &gt; &lt; TABLE &gt;

(Comparative Example 2)

A sodium secondary battery was prepared in the same manner as in Example 1, except that a negative electrode in which sodium foil was laminated on a general flat plate copper collector instead of a copper foil was used as the negative electrode.

[Experimental Example: Short Circuit Measurement of Sodium Secondary Battery]

The sodium secondary batteries prepared in the above-mentioned Examples and Comparative Examples were subjected to repetition of charging at a current density of 0.1 C and discharging at a current density of 0.1 C, and the time point at which the battery was short-circuited was measured and shown in Table 1 below.

division Cycle of battery Example 1 300 Example 2 More than 400 Example 3 More than 400 Example 4 320 Example 5 260 Example 6 170 Comparative Example 1 130 Comparative Example 2 110

Referring to Table 1, it can be seen that the battery is short-circuited when the cycle time of the sodium secondary battery manufactured in the embodiment is longer than that of the sodium secondary battery manufactured in the comparative example.

This is because, in the case of the sodium secondary battery manufactured in the above embodiment, the anode active material is dispersed in the pores of the porous current collector, so that the electrons in the electrode can be uniformly distributed and the surface area of the electrode is increased to reduce the current density per unit area And the growth of the dendrite can be suppressed, so that it is possible to prevent the short circuit of the battery.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (16)

A porous collector including a plurality of pores, and
And a negative electrode active material positioned in the pores of the porous current collector,
Wherein the negative electrode active material is a negative electrode for a sodium secondary battery comprising any one or a mixture of two or more selected from the group consisting of metal sodium and sodium alloys,
Wherein the porous collector is selected from the group consisting of Cu, Ni, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Sn, Bi, Si, Sb, Based material, and at least one selected from the group consisting of a metal-based material,
Wherein the negative electrode active material is contained in an amount of 5 to 50 wt% based on the total weight of the negative electrode for a sodium secondary battery. The method according to claim 1,
Wherein the porous current collector has a three-dimensional mesh pore structure in which the plurality of pores are connected to each other,
Wherein the anode active material is located within the three-dimensional mesh pore structure and forms a three-dimensional mesh structure within the porous current collector. The method according to claim 1,
Wherein the porous collector has a porosity of 50 to 99% by volume and an average diameter of the pores is 5 to 500 占 퐉. delete The method according to claim 1,
Wherein the sodium alloy is one selected from the group consisting of Al, Sn, Bi, Si, Sb, B, and alloys thereof, and an alloy of sodium and sodium. The method according to claim 1,
The porous collector may contain at least one of Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, W, Ag, Au, Ru, Pt, Ir, Al, Sn, Bi, Wherein the negative electrode further comprises any one or two or more metals selected from the group consisting of these alloys. The method according to claim 1,
Wherein the porous current collector further comprises a binder in pores of the porous current collector. The method according to claim 1,
And a negative electrode active material layer disposed on at least one side of the porous current collector. delete The method according to claim 1,
Wherein the negative electrode for a sodium secondary battery includes a protective layer positioned on the porous current collector,
Wherein the protective layer comprises a sodium ion conductive polymer. 11. The method of claim 10,
The sodium ion conductive polymer may be at least one selected from the group consisting of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), polyethylene oxide (PEO) Wherein the negative electrode is a negative electrode. 11. The method of claim 10,
Wherein the protective layer has a thickness of 0.1 占 퐉 to 20 占 퐉. At least one of the porous porous body containing a plurality of pores is formed by using at least one method selected from the group consisting of melt impregnation, vapor deposition, electroplating, roll pressing and slurry application of an anode active material capable of occluding and releasing sodium Coating and filling into one surface and into the pores,
The method of manufacturing an anode for a sodium secondary battery according to claim 1, wherein the negative electrode active material comprises any one or a mixture of two or more selected from the group consisting of metal sodium and sodium alloys. 14. The method of claim 13,
Applying and filling the negative electrode active material, and then pressing the negative electrode active material. In an electrode assembly in which an anode and a cathode are alternately stacked with a separator as a boundary,
The electrode assembly for a sodium secondary battery according to any one of claims 1 to 3, 5 to 8, and 10 to 12. A sodium secondary battery comprising an electrode assembly according to claim 15.