KR101206262B1 - Secondary battery using eutectic mixture electroyte and tin alloy anode - Google Patents

Abstract

The present invention provides a secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the electrolyte includes an eutectic mixture, and the negative electrode has a potential window area of a eutectic mixture with respect to lithium (Li / Li ⁺ ). It provides a secondary battery comprising a tin-containing compound corresponding to the negative electrode active material and an electrolyte for a secondary battery comprising the eutectic mixture.

In the secondary battery according to the present invention, a eutectic mixture is prepared by using a eutectic mixture-containing electrolyte and a negative electrode containing a tin-containing compound having a potential (Li / Li ⁺ ) relative to lithium in the potential window region of the eutectic mixture. It is possible to solve the decomposition of electrolyte solution and the degradation of the battery caused by using it as a battery electrolyte, and also to improve the safety and performance of the battery through thermal, chemical stability, high conductivity, and wide potential window of eutectic mixture. .

Lithium Secondary Battery, Electrolyte, Eutectic Mixture, Amide Group Compound, Tin

Description

Secondary battery using eutectic mixture electrolyte and tin alloy negative electrode {SECONDARY BATTERY USING EUTECTIC MIXTURE ELECTROYTE AND TIN ALLOY ANODE}

1 is a cross-sectional structural view of a coin type secondary battery.

FIG. 2 is a graph showing the capacity change of the lithium secondary battery of Example 1 in which a negative electrode using a tin-based amorphous composite oxide (TCO) -based material as a negative electrode active material and an electrolyte containing a eutectic mixture are used in combination.

3 is a graph showing a capacity change of the lithium secondary battery of Example 2 in which a negative electrode using a tin-sed amorphous composite oxide (TCO) -based material as a negative electrode active material and an electrolyte containing a eutectic mixture are used in combination; .

Figure 4 is a graph showing the capacity change of the lithium secondary battery of Comparative Example 1 using a negative electrode and a eutectic mixture containing electrolyte using a tin oxide as a negative electrode active material.

5 is a graph showing the capacity change of the lithium secondary battery of Comparative Example 2 using a negative electrode and a eutectic mixture-containing electrolyte in combination with a conventional graphite carbon as a negative electrode active material.

6 is a graph showing the capacity change of the lithium secondary battery of Comparative Example 3 using a negative electrode and an ionic liquid electrolyte using a tin alloy (TCO) based material as a negative electrode active material.

≪ Description of reference numerals &

1: anode, 2: cathode, 3: separator and electrolyte, 4: spacer,

5: coin can container, 6: coin can lid, 7: seal rubber

The present invention relates to a secondary battery having improved safety and performance at the same time by using a eutectic mixture-containing electrolyte and a negative electrode having a potential (Li / Li ⁺ ) relative to lithium in the potential region of the eutectic mixture.

Recently, interest in energy storage technology is increasing. As the field of application extends to mobile phones, notebook PCs, and even electric vehicles, research and development on energy storage is becoming concrete. In this respect, the most interesting field is an electrochemical device, and among them, a rechargeable battery capable of charging and discharging is drawing attention. Recently, research and development on the design of new electrodes and batteries have been conducted in order to improve the capacity density in developing such batteries.

Lithium-ion batteries, developed in the early 1990s, are widely used in the field of secondary batteries, which have higher operating voltage and higher energy density than conventional batteries such as Ni-MH, ni-Cd, and sulfuric acid-lead secondary batteries. I am getting it. In general, in a lithium ion battery, a lithium metal oxide is used for the positive electrode, a carbon material or a lithium metal alloy for the negative electrode, and a solution in which lithium salt is dissolved in an organic solvent as the electrolyte is used. Currently widely used organic solvents include ethylene carbonate, propylene carbonate, dimethoxyethane, gamma butyrolactone, N, N-dimethylformamide, tetrahydrofuran or acetylnitrile. However, such organic solvents generally have high flammability and high flammability, and thus have problems in safety during overcharge, overdischarge, short circuit, and high temperature in application to lithium ion secondary batteries.

In order to solve this problem in recent years, there have been many attempts to use nonflammable ionic liquids as electrolytes for lithium ion batteries in Japanese Patent Nos. 11-86905, 11-260400 and 2002-110225. This liquid was reduced at a higher voltage than lithium ions at the cathode, or imidazolium and ammonium cations were inserted together with the lithium ions to the cathode. As a result, when the imidazolium or ammonium-based ionic liquid was applied alone as a liquid electrolyte of a lithium secondary battery, the capacity reduction of the secondary battery in the charge-discharge cycle was very large, and thus it was not suitable for application to an actual secondary battery. In addition, due to problems such as the reaction between the ionic liquid and the carbon-based negative electrode, high viscosity, it has not been put to practical use yet.

Therefore, in order to overcome the disadvantages of the existing organic electrolytes and ionic liquids, attempts have been made to modify electrode materials or to find new electrode materials, and attempts have been made to develop new electrolytes including additives.

In view of the above-described problems, the inventors of the present invention have not only safety problems such as evaporation and ignition of electrolytes that occur when an organic solvent is used as an electrolyte when an eutectic mixture having economical and thermal and chemical stability is used as a component of a battery electrolyte. In addition, the problem of decomposition due to the high reduction potential of the material itself when using the general ionic liquid, the interference effect of the insertion of lithium ions due to the presence of two cations, the complex synthesis process and the purification of the complex problems are solved. At the same time, it was found that due to the excellent conductivity of eutectic mixtures and the wide electrochemical window, the performance of the cell was simultaneously improved.

However, when the electrolyte containing the eutectic mixture is used in combination with the carbon material, which is a conventional negative electrode material, the electrolyte is decomposed due to the electrochemical reaction of the negative electrode occurring at the potential outside the potential window of the eutectic mixture, and thus It was recognized that performance degradation is necessarily incurred.

Accordingly, the present invention improves safety and performance by using a cathode and a eutectic mixture-containing electrolyte in combination with a cathode active material of a tin-containing compound having a potential (Li / Li ⁺ ) relative to lithium as described above in the potential window of the eutectic mixture. At the same time, an object of the present invention is to provide a secondary battery.

The present invention provides a secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the electrolyte includes a eutectic mixture, and the negative electrode contains tin in which a potential (Li / Li ⁺ ) relative to lithium corresponds to a potential window region of the eutectic mixture. It provides a secondary battery, preferably a lithium secondary battery and a secondary battery electrolyte containing the eutectic mixture, characterized in that the compound comprises a negative electrode active material.

Hereinafter, the present invention will be described in detail.

The present invention, as a component of the secondary battery, using a eutectic mixture-containing electrolyte and a tin-containing compound having a lithium potential (Li / Li ⁺ ) corresponding to the electrochemical window region of the eutectic mixture as a negative electrode active material (竝 用It is characterized by.

Eutectic mixtures, like the known ionic liquids (IL), have high electrical conductivity, wide electrochemical window, non-flammability, wide temperature range as liquid, high solvation capability, non-coordinated binding properties, etc. It has physicochemical properties as an environmentally friendly solvent that can replace the flowable organic solvent of. In addition, since it is easier to synthesize than the ionic liquid and has a high flame retardancy, a high ion concentration, and a wide electrochemical window (0.5 to 5.5 V), it can be expected to have a wider application range. However, when the secondary battery is constructed by using the above-mentioned eutectic mixture alone and the carbon material, which is the negative electrode material, in combination with the potential outside the potential window of the eutectic mixture, for example, in the range of 0 to 0.5 V, Due to the electrochemical reaction, decomposition of the electrolyte and thereby deterioration of the secondary battery are inevitably caused.

That is, when the electrochemical reaction occurs outside the potential window of the electrolyte at the negative electrode or the positive electrode during charge and discharge of the battery, decomposition of the electrolyte is caused. For example, when a carbon material having a potential of less than 0 to 0.5 V relative to lithium and a eutectic mixture having an electrochemical window of 0.5 V or more are used as an electrolyte as a negative electrode material, the reduction reaction of the negative electrode outside the potential window of the eutectic mixture as an electrolyte during initial charging is performed. As the eutectic mixture decomposes, the initial capacity and life characteristics of the battery decrease rapidly.

Accordingly, in the present invention, it is recognized that the above-described reduction in initial capacity and life characteristics of the battery is associated with decomposition of the eutectic mixture during initial charging, and the potential (Li / Li ⁺ ) relative to lithium corresponds to the potential window region of the eutectic mixture. By using a tin-containing compound, preferably a tin-based amorphous oxide (TCO) -based material as a negative electrode active material, it is possible to fundamentally solve the decomposition of the electrolyte and the resulting degradation of the battery. In addition, since the tin-containing compound has a reduction reaction at 0.5 V, it is possible to prevent the reduction decomposition of the electrolyte and the decrease in capacity due to the conventional carbon material, and the theoretical capacity is also 1.5 times larger than carbon, thereby achieving high capacity. There is this.

The negative electrode active material of the present invention is not particularly limited as long as it has a tin-containing compound corresponding to the potential window region of the above-described eutectic mixture with respect to lithium (Li / Li ⁺ ). More specifically, it is possible to use tin-containing compounds having a potential (Li / Li ⁺ ) of 0.5 V or more so that the potential relative to lithium is included in the potential window region of the eutectic mixture. Since the tin-containing compound has an electrochemical reaction at 0.5 V or more within the potential window region of the eutectic mixture, the electrolyte does not decompose even when used in combination with an eutectic mixture-containing electrolyte unlike a conventional carbon material having a potential relative to lithium of 0 to 0.5 V. The performance of the battery can be improved.

The tin-containing compound may be an oxide-type tin alloy (TCO: tin-based amorphous composite oxide) -based material containing at least two elements selected from (i) tin, (ii) group 13 and group 15 elements, or (Iii) It is preferable that it is a compound which contains the chalcogenide compound or the metal oxide in the tin of (i) or the tin alloy (TCO) type | system | group material of said (ii).

That is, in the tin alloy (TCO) -based material, Sn-O, which is anisotropic, is uniformly dispersed, and B ₂ O ₃ , P ₂ O ₅ , Al ₂ O _3, etc. form an irregular network structure and the Sn-O It is an amorphous structure surrounding O. Since the tin alloy (TCO) -based material having such a structure does not react with Li even when Sn reacts with Li, unlike the conventional tin oxide, the tin alloy (TCO) -based material can suppress the volume change of the negative electrode active material generated during charging and thus cycle characteristics are improved. great.

In particular, as the negative electrode active material of the present invention, a tin-containing compound containing at least one chalcogenide compound, a metal oxide, or a mixture thereof in the tin or tin alloy (TCO) -based material may be used. In the case of a general Sn-O bond-containing compound, tin-containing compounds such as SnO ₂ or SnO are reduced by the reaction with Li ⁺ to form Li ₂ O as shown in Scheme 1 below, and thus, irreversible capacity increases in the first cycle. Life may be reduced.

^{_{SnO 2 + 2 Li + + 2}} e - → SnO + Li 2 O

^{SnO + 2 Li + + 2 e} - → Sn + Li 2 O

^{Sn + x Li + + xe -} → Li x Sn

On the other hand, after introducing one or more of the chalcogenide compounds, metal oxides or mixtures thereof into the tin or tin alloy (TCO) -based material, and heated at a temperature of about 500 to 2000 ℃, chalcogenide compounds, metal A tin-containing compound having no Sn-O bond can be obtained by an oxide or the like. When the tin-containing compound without Sn-O bond is used as a negative electrode active material, Li ₂ O is not formed by reaction with lithium ions present in the electrolyte during the first charge, thereby improving the lifespan and initial charge and discharge efficiency of the electrode. In addition, the effect of suppressing the volume change of the above-described negative electrode active material can be obtained at the same time.

The chalcogenide compound is not particularly limited as long as it is known in the art, and may be, for example, a compound containing at least one element selected from Group 16 elements of the periodic table, preferably 1 selected from the group consisting of S, Se, and Te. It is a compound containing an element or more of species. The metal oxide is preferably one metal oxide selected from the group consisting of MgO and CaO, but is not limited thereto, and conventional metal oxides may be used.

The tin-containing compound of the present invention may be represented by the following Chemical Formula 1, but is not limited thereto.

SnB _a P _b Al _c S _d Se _e Te _f Ca _l Mg _m O _n

In Formula 1, a, b, c, d, e, f, l, m, and n are each independently a real number of 0 or more and 1 or less, provided that a = b = c = d = e = f = l except where = m = n = 0).

The component constituting the battery electrolyte of the present invention is an eutectic mixture.

The eutectic mixture generally refers to a substance in which two or more substances are mixed to lower the melting temperature, and particularly refers to a mixed salt that is liquid at room temperature. Normal temperature means 100 degreeC here and 60 degreeC in some cases.

One of the components constituting the eutectic mixture is preferably an amide group-containing compound having two polar groups, a carbonyl group and an amine group in the molecule, but having two or more polar functional groups such as an acidic functional group and a basic functional group at the same time. The compound is not particularly limited. The polar functional groups form a eutectic mixture by acting as a complexing agent that weakens the bond between the cation and the anion of the ionizable salt, thereby reducing their melting temperature. In addition to the aforementioned functional groups, compounds that can form eutectic mixtures by including two different polar functional groups in the molecule, which can weaken the binding of the cation and anion of the ionizable salt, are also within the scope of the present invention.

The amide group-containing compound may be a linear, cyclic or mixed form of a structure containing an amide group, and non-limiting examples thereof include alkyl amides, alkenylamides, arylamides or allylamide compounds having 1 to 10 carbon atoms. Etc. Both primary, secondary or tertiary amide compounds can be used. In particular, cyclic amides having a wider potential window are preferred because they do not readily decompose because the number of hydrogens in the amine groups is small and stable at high voltages. Specific examples of the amide-based compound that can be used include acetamide, N-ethylacetamide, urea, methylurea, caprolactam, N-methylcaprolactam, N-ethylurethane, N-methyloxazolidinone and N-hexyloxazolidinone , Valerolactam, trifluoroacetamide, methyl carbamate, N-methylmethylcarbamate, N, N-dimethylmethylcarbamate, ethyl carbamate, butyl carbamate, formamide, formate, or mixtures thereof. .

As another component of the eutectic mixture of the present invention, any ionizable lithium-containing salt may be used. Non-limiting examples of lithium salts include lithium nitrate, lithium acetate, lithium hydroxide, lithium sulfate, lithium alkoxide, lithium halide, lithium oxide, lithium carbonate, lithium oxalate and the like. Specifically LiN (CN) ₂ , LiClO ₄ , Li (CF ₃ ) ₃ PF ₃ , Li (CF ₃ ) ₄ PF ₂ , Li (CF ₃ ) ₅ PF, Li (CF ₃ ) ₆ P, Li (CF ₃ CF ₂ SO ₂ ) ₂ N, Li (CF ₃ SO ₂ ) ₂ N, LiCF ₃ SO ₃ , LiCF ₃ CF ₂ (CF ₃ ) ₂ CO, Li (CF ₃ SO ₂ ) ₃ C, LiCF ₃ (CF ₂ ) ₇ SO ₃ , LiCF ₃ CO ₂ , LiCH ₃ CO ₂ or mixtures thereof are preferred.

The eutectic mixture of the present invention may be represented by the following Chemical Formula 2 or Chemical Formula 3, but is not limited thereto:

In Formula 2, R ₁ , R ₂ and R are each independently hydrogen, halogen, alkyl group having 1 to 20 carbon atoms, alkylamine group, alkenyl group or aryl group; X is selected from hydrogen, carbon, silicon, oxygen, nitrogen, phosphorus and sulfur, provided that m = 0 if X is hydrogen, m = 1 if X is oxygen or sulfur, and X is nitrogen or phosphorus M = 2, and when X is carbon or silicon, m = 3, wherein R is each independently), and Y is anion capable of forming a salt with lithium.

In Formula 3, R ₁ and R are hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkylamine group, an alkenyl group, an aryl group or an allyl group; X is selected from hydrogen, carbon, silicon, oxygen, nitrogen, phosphorus and sulfur, provided that m = 0 and n = 0 if X is hydrogen, m = 0 if X is oxygen or sulfur and X is M = 1 when nitrogen or phosphorus, m = 2 when X is carbon or silicon, and each R is independent); n is an integer from 0 to 10, wherein when n is 1 or more, X is selected from carbon, silicon, oxygen, nitrogen, phosphorus, sulfur except hydrogen; Y is anion that can form a salt with lithium.

In the compound represented by Formula 2 or Formula 3, Y, which is an anion of lithium salt, is not particularly limited as long as it is anion capable of forming a salt with lithium, and non-limiting examples thereof include F ⁻ , ^{Cl -, Br -, I -} , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, RSO 3 -, RCOO -; _{^{PF 6 -, (CF 3)}} 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, (CF 3 _{^{SO 3 -) 2, (CF}} 2 CF 2 SO 3 -) 2, (CF 3 SO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, ( ^{_{SF 5) 3 C -, (}} CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and the like ^{_{-, (CF 3 CF 2 SO}} 2) 2 N.

As described above, the amide group-containing compound and the lithium salt (LiY), which are constituents of the eutectic mixture, are coordinated with the carbonyl group (-C = O) and Li cation (Li ⁺ ) of the lithium salt in the amide compound as shown in Scheme 2 below. A bond of Li-Y is achieved by forming a hydrogen bond between the anion (Y ⁻ ) of the lithium salt and the amine group (—NH ₂ ) in the amide compound. As a result, the melting point of the amide group-containing compound and the lithium salt, which existed in the solid state, is lowered to form a eutectic mixture in liquid form at room temperature.

The melting temperature of the eutectic mixture according to the present invention is not particularly limited, but is preferably in a liquid state at 100 ° C. or lower, more preferably at room temperature. In addition, the viscosity (viscosity) of the eutectic mixture is also not particularly limited, 100 cP or less is preferred.

The eutectic mixture of the present invention may be prepared according to a conventional method known in the art, for example, an amide group-containing compound and a lithium salt are mixed at room temperature, reacted by adding a suitable temperature of 70 ° C. or lower, and then purified. It can be manufactured by. At this time, the mole% ratio of the amide compound and the lithium salt is suitably 1: 1 to 8: 1, and particularly preferably 2: 1 to 6: 1.

When the eutectic mixture is provided as an electrolyte component, 1) due to the physical properties of the eutectic mixture, for example, due to the physical stability of the eutectic mixture itself, it exhibits a wider potential window than conventional organic solvents and ionic liquids. The operating voltage range of the secondary battery can be extended.

2) In addition, the eutectic mixture contained in the electrolyte of the present invention has no vapor pressure as compared to the conventional solvent, there is no problem of evaporation and exhaustion of the electrolyte, and it is possible to improve the safety of the electrochemical device by having flame retardancy. In addition, since the eutectic mixture itself is a very stable form, it is possible to realize side reaction suppression in the battery, and to improve performance through high conductivity.

3) In addition, since a lithium salt is contained in the eutectic mixture as a constituent of the eutectic mixture, an additional lithium salt is not required even in the case of a lithium secondary battery in which lithium ions should be inserted and detached into a positive electrode active material. There is an advantage.

4) Furthermore, when the conventional ionic liquid is used as the electrolyte of the lithium secondary battery, there is a problem in that the initial capacity of the secondary battery and the capacity decrease of the secondary battery after the third cycle are very large in the charge / discharge cycle. The initial capacity of the secondary battery and the decrease in capacity after the cycle is associated with a solid electrolyte interface (SEI) membrane, which is an inert film formed on the surface of the anode during initial charging. Due to the reduction decomposition at a higher voltage than lithium ions at the cathode. In addition, the ionic liquid contains two or more organic cations larger than lithium ions in itself, such as imidazolium and ammonium cations, which travel faster than lithium ions and reach and surround the cathode first. . This not only prevents the smooth movement of lithium ions to be inserted into the negative electrode, but also causes a problem that lithium ions and the organic cations are inserted together in the negative electrode.

In contrast, in the present invention, electrolyte decomposition can be avoided by using not only a eutectic mixture having a high potential window but also a tin-containing compound corresponding to a lithium potential in the potential window region of the eutectic mixture as a negative electrode material. In addition, since only lithium ions (Li ⁺ ) exist as cations in the eutectic mixture itself, the interference effect of the negative electrode insertion of lithium ions is fundamentally solved, and smooth movement of lithium ions can be achieved to improve battery performance. have.

Electrolyte Containing Eutectic Mixture

The electrolyte comprising the eutectic mixture according to the present invention can be applied regardless of the form, but preferably in two embodiments, liquid or gel polymer electrolyte.

1) The first embodiment of the electrolyte according to the present invention is an electrolyte in the form of a eutectic mixture-containing liquid, which may be made by using a eutectic mixture composed of the aforementioned amide group-containing compound and a lithium-containing ion-bonding salt alone. . At this time it may further comprise a conventional electrolyte additive component known in the art.

2) A second embodiment of the electrolyte according to the invention is an electrolyte in the form of a gel polymer containing a eutectic mixture. Since the gel polymer plays a role of supporting the eutectic mixture, there is an advantage in that the electrolyte leakage problem is solved and the device can be thinned and processed in the form of a film.

The gel polymer electrolyte may be prepared according to conventional methods known in the art, and the following three forms may be applied to the preferred embodiment thereof. In this case, the above-described electrolyte additive component may also be included.

① First, the polymerization of monomers is carried out in the presence of eutectic mixtures to form gel polymer electrolytes. The gel polymer may be formed by polymerization of such monomers by In - Situ polymerization in the electrochemical device, or after formation of the gel polymer electrolyte, it may be introduced into the electrochemical device.

The above-mentioned gel polymer electrolyte includes (i) a eutectic mixture composed of an amide group-containing compound and a lithium-containing ion-bonding salt; And (ii) polymerizing an electrolyte precursor liquid (pre-gel) containing a monomer capable of forming a gel polymer by a polymerization reaction.

The monomer may be used without particular limitation as long as it can form the gel polymer by polymerization, and non-limiting examples thereof include vinyl monomers. When the vinyl monomer is mixed with the eutectic mixture to form a gel polymer, transparent polymerization is possible, and the polymerization conditions are very simple.

Non-limiting examples of vinyl monomers that can be used include acrylonitrile, methyl methacrylate, methyl acrylate, methacrylonitrile, methyl styrene, vinyl esters, vinyl chloride, vinylidene chloride, acrylamide, tetrafluoroethylene , Vinyl acetate, methyl vinyl ketone, ethylene, styrene, paramethoxy styrene, paracyano styrene and the like. In addition, it is preferable that the monomer has a low volume shrinkage during polymerization and is capable of in-situ polymerization in an electrochemical device.

Since the polymerization reaction of the above-described monomer (monomer) is generally made through heat irradiation, the electrolyte precursor liquid may include a polymerization initiator.

Initiators decompose by heat to form radicals, and react with monomers by free radical polymerization to form gel polymer electrolytes. Moreover, superposition | polymerization of a monomer can also be advanced, without using an initiator. In general, free radical polymerization is a reaction of initiation where active molecules or active points are formed, a growth reaction in which monomers are added at the end of an active chain to form an active point at the end of a chain, and a chain transfer reaction that moves an active point to other molecules. In addition, the reaction chain undergoes a stop reaction in which the active chain center is destroyed.

Non-limiting examples of thermal polymerization initiators that can be used include organic peroxides such as Benzoyl peroxide, Acetyl peroxide, Dilauryl peroxide, Di-tert-butyl peroxide, Cumyl hydroperoxide, Hydrogen peroxide, and hydroperoxides, 2,2-Azobis (2- azo compounds such as cyanobutane), 2,2-Azobis (Methylbutyronitrile), AIBN (Azobis (iso-butyronitrile), AMVN (Azobisdimethyl-Valeronitrile), and organic metals such as alkylated silvers.

The mixing ratio of the electrolyte precursor liquid to form the gel polymer electrolyte of the present invention is a weight ratio of (eutectic mixture) x: (monomer capable of forming the gel polymer by polymerization) y: (polymerization initiator) z, x is 0.5-0.95, y are 0.05-0.5, z is 0.00-0.05, and it is preferable that x + y + z = 1. More preferably, x is 0.7-0.95, y is 0.05-0.3, and z is 0.00-0.01. However, the present invention is not limited thereto.

The electrolyte precursor liquid for gel polymer formation may optionally contain other additives known in the art, in addition to the above components.

In-Situ polymerization according to the present invention, as described above, the polymerization is initiated through heat to complete the formation of the gel polymer electrolyte. At this time, the degree of polymerization of the gel polymer will depend on the reaction factors, that is, the polymerization time and polymerization temperature in the case of thermal polymerization. Therefore, the degree of gel polymer polymerization can be appropriately controlled by controlling the polymerization time and polymerization temperature which are reaction factors. At this time, the polymerization time depends on the type of initiator and the polymerization temperature. Preferably, the gel polymer electrolyte does not leak during the polymerization, and it is required that the electrolyte is not polymerized to shrink the volume. For example, the polymerization time takes about 20 to 60 minutes, the thermal polymerization temperature is about 40 to 80 ℃.

② Second, the eutectic mixture is impregnated with the polymer or gel polymer already formed through the injection of the eutectic mixture.

Non-limiting examples of polymers that can be used include polymethylmethacrylate, polyvinylidene difluoride, polyvinyl chloride, polyethylene oxide, polyhydroxyethylmethacrylate, and the like. In addition, all conventional gel polymers known in the art can be used. Using this impregnation method has an advantage that the manufacturing process can be simplified compared to the In-Situ method described above.

③ Third, the polymer and eutectic mixture are dissolved in a solvent and then the solvent is removed to form a gel polymer electrolyte. At this time, the eutectic mixture is in the form contained in the polymer matrix of the aforementioned components.

There is no restriction | limiting in particular as a solvent which can be used, For example, the general organic solvent used for a battery can also be used. Non-limiting examples of these include Toluene, Acetone, Acetonitrile, THF, Propylene carbonate (PC), Ethylene carbonate (EC), Diethyl carbonate (DEC), Dimethyl carbonate (DMC), Dipropyl carbonate (DPC), Dimethyl sulfoxide , Acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone (GBL), or mixtures thereof. . Since the organic solvent may impair the safety of the secondary battery due to flammability, it is preferable to use a small amount if possible. In addition, a phosphate ester may be used as a flame retardant additive mainly used in lithium secondary batteries, and non-limiting examples thereof include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, tripropyl phosphate, tributyl phosphate, and mixtures thereof. .

The solvent removal method is also not particularly limited, and is made through heating according to a conventional method. In the third embodiment, a post-treatment process may be required to remove the solvent when forming the gel polymer electrolyte. However, it is also possible to improve the lithium ion conductivity of the electrolyte by not including solvent removal completely so that a part of the solvent in the gel polymer electrolyte is included.

Secondary Battery with Electrolyte-Containing Electrolyte

The secondary battery of the present invention may be composed of a negative electrode, a positive electrode, an electrolyte and a separator as shown in FIG.

In the present invention, all the batteries which have a continuous electrochemical reaction through charge and discharge are referred to as secondary batteries. Particularly preferred are lithium secondary batteries, and non-limiting examples thereof include lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries or lithium ion polymer secondary batteries.

The method for manufacturing the secondary battery of the present invention can be used a conventional method known in the art, for example, after the assembly between the positive electrode through the separator, the eutectic mixture It is prepared by injecting an electrolyte comprising a.

At this time, the positive electrode and the negative electrode according to the present invention to prepare an electrode slurry comprising an electrode active material, that is, a positive electrode active material and a negative electrode active material in accordance with conventional methods known in the art, and apply the prepared electrode slurry to each current collector Thereafter, the solvent or the dispersion medium may be removed by drying to bind the active material to the current collector, and the active material may be bound to each other. In this case, a small amount of a conductive agent and / or a binder may be optionally added.

As the negative electrode active material of the electrode active material, a tin-containing compound, preferably a tin alloy (TCO) -based material, included in the potential window region of the eutectic mixture where lithium potential (Li / Li ⁺ ) is used as an electrolyte component may be used. .

The tin-containing compound may be prepared by mixing and sintering tin or tin oxide with a group 13 element-containing compound and a group 15 element-containing compound, respectively, or additionally mixing and sintering chalcogenide and / or metal oxide, respectively. As a preferred example of the preparation method, SnO, B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ are mixed in a molar ratio Sn: B: P: Al = 5: 3: 3: 2 and then the mixture is ground. The mixed powder is placed in an alumina crucible and heat-treated under argon conditions and at a temperature of 1100 ° C. for at least 10 hours. After the heat treatment, the molten product is slowly cooled at a rate of 10 to 20 ° C./minute, and the resulting yellow colored transparent solid may be powdered again to be used as a negative electrode active material.

The positive electrode active material of the electrode active material can be used if it is a conventional cathode active material such as lithium metal oxide or chalcogenide compound. The lithium metal oxide is a lithium-containing oxide including at least one element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, transition metals and rare earth elements, and examples thereof include LiCoO. ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCrO ₂ , LiFePO ₄ , LiFeO ₂ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO ₄ , LiCoVO ₄ , LiCr _x Mn _2-x O ₄ , LiNiVO ₄ , LiNi _x Mn _2-x O ₄ , Li _2-x CoMn ₃ O _8, or mixtures thereof. In addition, non-limiting examples of the chalcogenide compound include TiS ₂ , SeO ₂ , MoS ₂ , FeS ₂ , MnO ₂ , NbSe ₃ , V ₂ O ₅ , V ₆ O ₁₃ , CuCl _2, or mixtures thereof. .

The separator may use a porous material that blocks internal short circuits of both electrodes and impregnates the electrolyte. Non-limiting examples thereof include a polystyrene-based, polypropylene-based, polycarbonate-based porous separator or a composite porous separator in which an inorganic material is added to the porous separator.

Meanwhile, the electrolyte may include additives for preventing overcharge and forming a passivation layer in addition to the eutectic mixture.

That is, when an electrochemical reaction occurs outside the potential window of the electrolyte at the negative electrode or the positive electrode during charge-discharge of the battery, decomposition of the electrolyte may occur, thereby degrading the performance of the battery. Thus, in the present invention, by adding an additive to the electrolyte, a passivation film, that is, a protective film, which prevents decomposition of the electrolyte can be formed. The protective film may pass through lithium ions in an initial charge-discharge cycle and serve to prevent decomposition of the electrolyte. Non-limiting examples of the passivation film forming additives include 12-crown-4, 18-crown-6, catecholcarbonate, vinylene carbonate, ethylene sulfite, methylchloroformate, susinimide, methyl cinnamate, and the like. .

In addition, to the electrolyte according to the present invention, an overcurrent consumption additive may be added to prevent overvoltage caused by the flow of overcurrent at the anode. Non-limiting examples of the overvoltage protection additives include iodine, butyl ferrocene, tricyanobenzene, tetrashinanoquinomethane, benzene derivatives, pyrocarbonate, cyclohexylbenzene, and the like.

In addition to the aforementioned components, a conductive elastic material may be further used to fill the remaining space of the secondary battery.

The shape of the secondary battery, preferably the lithium secondary battery, manufactured by the above method is not particularly limited, and may be, for example, a cylindrical, square or pouch type of can.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited thereto.

[Examples 1 to 4. Preparation of Secondary Battery]

Example 1

1-1. Preparation of Cathode Active Material

Sn, B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ , S, CaO were mixed in a molar ratio Sn: B: P: Al: S: Ca = 5: 2: 2: 2: 1: 1. The mixture was placed in an Ar filled quartz tube, melted at 1000 ° C., and then cooled slowly to prepare a tin alloy (TCO) based material.

1-2. Preparation of Eutectic Mixture Containing Electrolyte

6 g of purified N, N-dimethylmethylcarbamate and 3 g of LiPF ₆ were placed in a round bottom flask, and stirred slowly for 12 hours in a room temperature nitrogen atmosphere to obtain 9 g of a eutectic mixture. The eutectic mixture was prepared by lowering the eutectic mixture to 20 ppm or less in 0.3 torr vacuum.

1-3. Fabrication of Secondary Battery

LiCoO ₂ as a positive electrode active material, artificial graphite as a conductive agent, polyvinylidene fluoride as a binder was mixed in a weight ratio of 94: 3: 3, and N-methylpyrrolidone was added to the obtained mixture to prepare a slurry. The prepared slurry was applied to aluminum foil, and dried at 130 ° C. for 2 hours to prepare a positive electrode.

As a negative electrode active material, the tin alloy (TCO) -based material powder, artificial graphite, and binder prepared in Example 1-1 were mixed at a weight ratio of 94: 3: 3, and N-methylpyrrolidone was added to prepare a slurry. The prepared slurry was applied to a copper foil and dried at 130 ° C. for 2 hours to prepare a negative electrode.

A positive electrode and a negative electrode prepared as described above were prepared in 1 cm 2, and a separator was interposed therebetween. Injecting the eutectic mixture-containing electrolyte solution prepared in Example 1-2 to finally complete the secondary battery as shown in FIG.

Example 2

2-1. Preparation of Cathode Active Material

The same method as in Example 1-1 was carried out except that SnO, B ₂ O ₃ , Sn ₂ P ₂ O ₇ , and Al ₂ O ₃ were mixed in a molar ratio Sn: B: P: Al = 5: 2: 2: 2. To prepare a tin alloy-based material.

2-2. Fabrication of Secondary Battery

A secondary battery was manufactured in the same manner as in Example 1, except that the tin alloy (TCO) -based material powder prepared in Example 2-1 was used as the negative electrode active material.

Example 3

LiMn ₂ O ₄ was used instead of LiCoO ₂ as the positive electrode, and other conditions were carried out in the same manner as in Example 1, to prepare a lithium secondary battery.

Example 4

LiNi _0.5 Mn _1.5 O ₄ was used instead of LiCoO ₂ as the positive electrode, and the other conditions were performed in the same manner as in Example 1, to prepare a lithium secondary battery.

Comparative Example 1

A lithium secondary material was prepared in the same manner as in Example 1 except that SnO ₂ was used as a negative electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder was mixed at a weight ratio of 85: 10: 5 to prepare a negative electrode. The battery was prepared.

Comparative Example 2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that a conventional carbon material was used instead of the tin alloy (TCO) prepared in Examples 1 to 2 as the negative electrode active material.

Comparative Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the ionic liquid EMI-BF ₄ was used instead of the eutectic mixture prepared in Example 1-2 as the electrolyte.

Experimental Example 1. Characterization of Secondary Battery

According to the present invention, the characteristics of the lithium secondary battery including the eutectic mixture-containing electrolyte and the tin alloy (TCO) -based negative electrode active material were analyzed as follows.

The eutectic mixture containing electrolyte and the negative electrode formed of a tin alloy-based negative electrode active material (Examples 1-1 and 2-1) having a potential (Li / Li ⁺ ) relative to lithium in the potential window region of the eutectic mixture are used in combination. The lithium secondary batteries of Examples 1 and 2 were used, and as a control thereof, the lithium secondary battery of Comparative Example 1 using a tin oxide anode and an eutectic mixture-containing electrolyte in combination with a conventional carbon material anode and an eutectic mixture-containing electrolyte was used. The lithium secondary battery of Comparative Example 3 using a lithium secondary battery of Comparative Example 2 in combination and a negative electrode formed from a tin alloy series negative electrode active material (Example 1-1) and an ionic liquid (EMI-BF ₄ ) electrolyte in combination was used.

As a result of the experiment, the characteristics of the secondary battery prepared in Example 1 obtained a discharge capacity of 96% at 20 charge-discharge cycles, the charge-discharge efficiency was 99% (see FIG. 2), and the secondary battery prepared in Example 2 As for the characteristic of the battery, the discharge capacity of 65% was obtained in one charge / discharge, and after that, the cycle of 99% of charge / discharge efficiency was maintained (refer FIG. 3). Since the operating potential of the negative electrode mentioned above is about 0.5 V relative to the lithium potential, the operating potential of the positive electrode is about 3.8 V, and the potential window of the eutectic mixture is 0.5 to 5.5 V, the operating voltage when constructing secondary batteries with these elements is It was found that about 3.3 V, excellent energy density, and stable to overcharge, short circuit and thermal shock.

On the other hand, the characteristics of the secondary battery of Comparative Example 1 using tin oxide as the negative electrode active material showed that the discharge capacity in one charge / discharge was about 50% lower than that of Example 1 or Example 2, and thereafter, the charge / discharge thereafter. A cycle of 90% efficiency was maintained (see FIG. 4). In addition, in the characteristics of the secondary battery of Comparative Example 2 using a conventional carbon material as the negative electrode active material, a rapid cycle was lowered after one charge and discharge, and a discharge capacity of almost 0% was obtained from five charge and discharge cycles. The charge-discharge efficiency was also about 70% or less (see FIG. 5). In addition, the characteristics of the secondary battery of Comparative Example 3 using the ionic liquid EMI-BF ₄ as the electrolyte showed a discharge capacity of almost 0% from six charge-discharge cycles. The charge-discharge efficiency was also about 70% or less (see FIG. 6). This proves that the performance of the battery is inevitably caused by the electrochemical reaction of the carbon material, the negative electrode material, which occurs at the potential beyond the potential window of the eutectic mixture as the electrolyte component.

Therefore, a lithium secondary battery using a eutectic mixture-containing electrolyte and a tin alloy (TCO) -based negative electrode containing a potential (Li / Li ⁺ ) relative to lithium in the potential window region of the eutectic mixture is excellent in terms of safety as well as performance. I could confirm it.

In the present invention, by using a eutectic mixture-containing electrolyte and a negative electrode containing a tin-containing compound contained in the potential window region of the eutectic mixture in combination with the eutectic mixture, decomposition of the electrolytic solution generated when the eutectic mixture is used as a battery electrolyte Not only can the performance degradation of the battery be solved, but also the thermal and chemical stability of the eutectic mixture, high conductivity, and a wide potential window can simultaneously provide the safety and performance of the battery.

Claims (17)

In a secondary battery having a positive electrode, a negative electrode, an electrolyte and a separator, The electrolyte includes an eutectic mixture, and the negative electrode includes a tin-containing compound having a potential (Li / Li ⁺ ) relative to lithium in the potential window region of the eutectic mixture, as a negative electrode active material. The negative electrode active material including the tin-containing compound has a potential of 0.5 V or more relative to lithium (Li / Li ⁺ ), The tin-containing compound is a tin-based amorphous composite oxide (TCO) -based compound containing at least two elements selected from the group 13 or group 15 elements, respectively, or the tin alloy (TCO) -based compound A secondary battery characterized in that the chalcogenide compound or a compound containing a metal oxide. delete delete delete The secondary battery of claim 1, wherein the tin-containing compound is prepared by mixing and sintering a chalcogenide compound or a metal oxide with a tin alloy (TCO) -based material, respectively. The secondary battery of claim 1, wherein the eutectic mixture is formed of an amide group-containing compound and an ionizable lithium salt. The secondary battery of claim 1, wherein the eutectic mixture is represented by the following Chemical Formula 2 or Chemical Formula 3: [Formula 2]

(In Formula 2, R ₁ , R ₂ and R are each independently hydrogen, halogen, alkyl group having 1 to 20 carbon atoms, alkylamine group, alkenyl group or aryl group; X is hydrogen, carbon, silicon, oxygen, Selected from nitrogen, phosphorus and sulfur, provided that m = 0 if X is hydrogen, m = 1 if X is oxygen or sulfur, m = 2 if X is nitrogen or phosphorus and X is carbon or M = 3 for silicon, where R is independent of each other, Y is anion capable of forming salts with lithium; (3)

(In Formula 3, R ₁ and R are hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkylamine group, an alkenyl group, an aryl group or an allyl group; X is hydrogen, carbon, silicon, oxygen, nitrogen, phosphorus and sulfur M = 0, n = 0 if X is hydrogen, m = 0 if X is oxygen or sulfur, m = 1 if X is nitrogen or phosphorus, and X is carbon or silicon M is 2 and R is independent of each other; n is an integer of 0 to 10, wherein when n is 1 or more, X is selected from carbon, silicon, oxygen, nitrogen, phosphorus, sulfur, except hydrogen; Y is anion capable of forming salts with lithium. The compound of claim 6, wherein the amide group-containing compound is acetamide, N-ethylacetamide, urea, methylurea, caprolactam, N-methylcaprolactam, N-ethylurethane, N-methyloxazolidinone, N-hexyl From the group consisting of oxazolidinone, valelactam, trifluoroacetamide, methyl carbamate, N-methylmethyl carbamate, N, N-dimethylmethyl carbamate, ethyl carbamate, butyl carbamate, formamide and formate A secondary battery characterized by at least one selected. The method of claim 6, wherein the lithium salt anion is ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, RSO 3 -, RCOO -; ^{_{PF 6 -, (CF 3)}} 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, (CF 3 ^{_{SO 3 -) 2, (CF}} 2 CF 2 SO 3 -) 2, (CF 3 SO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, ( ^{_{SF 5) 3 C -, (}} CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and _{(CF 3 CF 2 SO 2)} 2 N - secondary battery is characterized by at least one member selected from the group consisting of. The secondary battery of claim 1, wherein the electrolyte is a liquid type. The method of claim 1, wherein the electrolyte is (i) a eutectic mixture; And (ii) a gel polymer type formed by polymerizing an electrolyte precursor solution containing a monomer capable of forming a gel polymer by a polymerization reaction. The method of claim 11, wherein the monomer is acrylonitrile, methyl methacrylate, methyl acrylate, methacrylonitrile, methyl styrene, vinyl esters, vinyl chloride, vinylidene chloride, acrylamide, tetrafluoroethylene, A secondary battery characterized by at least one member selected from the group consisting of vinyl acetate, vinyl chloride, methyl vinyl ketone, ethylene, styrene, paramethoxy styrene, and paracyano styrene. The secondary battery of claim 11, wherein the electrolyte precursor liquid further comprises a polymerization initiator or a photoinitiator. 12. The method of claim 11, wherein the electrolyte in the battery is In - situ the characteristics that the secondary battery produced by polymerization. The secondary battery of claim 1, wherein the electrolyte is impregnated with a eutectic mixture in a polymer or a gel polymer. The secondary battery of claim 15, wherein the polymer is selected from the group consisting of polymethyl methacrylate, polyvinylidene difluoride, polyvinyl chloride, polyethylene oxide, and polyhydroxyethyl methacrylate. The secondary battery of claim 1, wherein the secondary battery is a lithium secondary battery.

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