KR20160037794A - Lithium Secondary Battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery which comprises: an anode; a cathode; a separation film disposed between the anode and the cathode; and a non-aqueous electrolyte having a lithium salt dissolved in a non-aqueous solvent. The separation film includes: a porous substrate; and an organic and inorganic composite separation film including a porous coating layer formed in at least one surface of the porous substrate, wherein the porous coating layer includes a plurality of inorganic particles, a polymer binder, and pores formed by interconnecting and fixing the inorganic particles by the polymer binder. The non-aqueous electrolyte includes: a lithium salt with concentration of 0.8-2 M; and a non-aqueous solvent with viscosity of 1.4-50 cP, and is highly viscous non-aqueous electrolyte with viscosity greater than or equal to 3.5 cP at 25°C.

Description

[0001] Lithium Secondary Battery [0002]

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery including a high viscosity non-aqueous electrolyte having high wettability and safety.

In recent years, demand for secondary batteries has been rapidly increasing due to explosive demand for portable electric and electronic devices. In particular, lithium secondary batteries are receiving the greatest attention in terms of high capacity.

The lithium secondary battery developed in the early 1990s is composed of a carbonaceous anode capable of intercalating and deintercalating lithium ions, a cathode made of a lithium-containing oxide, a separator interposed between the anode and the cathode, and a non-aqueous electrolyte.

The separation membrane of the lithium secondary battery uses a porous separator made of a polyolefin porous film or a polyester nonwoven fabric to increase the ionic conductivity based on a high porosity while electrically insulating the anode and the cathode.

The non-aqueous electrolyte is a mixed solution of a cyclic carbonate compound such as ethylene carbonate or propylene carbonate and a linear carbonate compound such as dimethyl carbonate, ethylmethyl carbonate or diethyl carbonate.

On the other hand, as the capacity of secondary batteries increases, importance of wetting of the electrolytic solution is increasing. If the impregnation (wetting) of the electrolyte solution is incomplete in the secondary cell manufacturing process, the capacity of the secondary battery is lowered, and the non-uniformity of the electrode state is intensified, so that the electrode reaction locally concentrates, It can cause serious problems in safety. The wetting failure of the electrolyte has a problem in that the life of the battery can be shortened by accelerating the degradation of the electrode even though other electrode states are good

In order to improve the wettability of the electrolytic solution, a method using a low viscosity organic solvent has been proposed. In this case, however, not only electrolyte leakage but also ignition and explosion when a secondary battery malfunctions occur, and safety is deteriorated.

In order to solve such a problem, attempts have been recently made to improve safety by including a non-aqueous solvent having a high viscosity (typically, viscosity of 1.4 cP or more at 25 캜) with a high flash point in the non-aqueous electrolyte.

However, when a non-aqueous solvent having a high viscosity is included in the non-aqueous electrolyte, the wettability of the porous separator is lowered, and the charge / discharge performance of the lithium secondary battery is greatly reduced, and charging and discharging are impossible.

In order to solve the above problems, the present invention provides a lithium secondary battery comprising a nonaqueous electrolyte solution having not only stability but also wetting effect on a porous separator.

In order to achieve the above object,

In one specific embodiment of the present invention

A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte solution in which a lithium salt is dissolved in a nonaqueous solvent,

The separation membrane comprises a porous substrate; And a porous coating layer formed on at least one surface of the porous substrate, wherein the porous coating layer is formed by a plurality of inorganic particles, a polymeric binder, and a polymeric binder, and the pores formed by connecting and fixing the inorganic particles to each other ≪ / RTI &

The nonaqueous electrolyte solution is a high viscosity nonaqueous electrolyte solution containing a lithium salt having a concentration of 0.8 M to 2 M and a nonaqueous solvent having a viscosity of 1.4 to 50 cP and having a viscosity of 3.5 cP or more at 25 캜.

According to the present invention, safety and wettability to a porous separator are improved by including a high viscosity non-aqueous electrolyte having a viscosity of at least 3.5 cP at 25 DEG C, and a lithium secondary battery having good charge-discharge characteristics can be produced.

Fig. 1 is a graph showing the results of evaluation of other charge-discharge characteristics in Experimental Example 1. Fig.
2 is a graph showing the results of evaluation of charge-discharge characteristics according to Experimental Example 2. FIG.
3 is a graph showing the results of the charge-discharge characteristic evaluation according to Experimental Example 3.
4 is a graph showing the results of evaluation of charge-discharge characteristics according to Experimental Example 4. FIG.

Hereinafter, the present invention will be described in detail. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the constitutions described in the embodiments described herein are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents which can be substituted at the time of application It should be understood that variations can be made.

First, in a specific embodiment of the present invention

A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte solution in which a lithium salt is dissolved in a nonaqueous solvent,

The separation membrane comprises a porous substrate; And a porous coating layer formed on at least one surface of the porous substrate, wherein the porous coating layer is formed by a plurality of inorganic particles, a polymeric binder, and a polymeric binder, and the pores formed by connecting and fixing the inorganic particles to each other ≪ / RTI &

The nonaqueous electrolyte solution is a high viscosity nonaqueous electrolyte solution containing a lithium salt having a concentration of 0.8 M to 2 M and a nonaqueous solvent having a viscosity of 1.4 to 50 cP and having a viscosity of 3.5 cP or more at 25 캜.

Specifically, the non-aqueous electrolyte may include a high viscosity non-aqueous electrolyte containing a lithium salt having a concentration of 0.8 M to 2 M and a non-aqueous solvent having a viscosity of 1.4 to 30 cP and having a viscosity of from 3.5 cP to 60 cP at 25 ° C.

More specifically, the non-aqueous electrolyte of the present invention may include a high viscosity non-aqueous electrolyte containing a lithium salt having a concentration of 0.8 M to 1.4 M and a non-aqueous solvent having a viscosity of 1.4 to 4.5 cP and having a viscosity at 25 ° C of 3.5 cP or more and 60 cP or less have.

The present inventors have found that when an organic / inorganic hybrid separator comprising the porous coating layer and a high viscosity non-aqueous electrolyte satisfying both the viscosity of the non-aqueous electrolyte and the concentration of the lithium salt are applied, not only the safety but also the wettability of the non- It was confirmed that a lithium secondary battery improved in charge / discharge characteristics can be manufactured.

Hereinafter, the lithium secondary battery of the present invention will be described in more detail as follows.

(a)

As described above, in the lithium secondary battery of the present invention,

A porous substrate; And a porous coating layer formed on at least one surface of the porous substrate,

The porous coating layer includes a plurality of inorganic particles, a polymeric binder, and pores formed by connecting and fixing the inorganic particles with the polymeric binder.

(i) a porous substrate

As the porous substrate of the organic / inorganic composite separator of the present invention, a conventional porous film or a porous nonwoven fabric may be used.

Typical examples of the porous film include polyolefin-based porous films formed of polyethylene, polypropylene, polybutylene, and polypentene either singly or in a mixture of two or more thereof.

In addition to the polyolefin-based nonwoven fabric, representative examples of the porous nonwoven fabric include polyesters such as polyethylene terephthalate or polybutylene terephthalate, polyamides such as polyacetal, polyester, and aramid, polycarbonate, polyimide, poly Polyether sulfone, ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, polytetrafluoroethylene, polyfluorinated vinylidene, polyvinyl chloride, polyacrylonitrile, cellulose, nylon, polyparaphenylene Benzobisoxazole, polyarylate, and glass, respectively, or a nonwoven fabric formed of a mixture of two or more thereof.

The thickness of the porous substrate constituting the organic / inorganic hybrid separation membrane of the present invention is not particularly limited, but is preferably 1 to 100 μm, and the pore size and porosity present in the porous substrate are also not particularly limited, And preferably 10 to 95%. When the pore size and porosity are within the above ranges, the mechanical properties and ion conductivity of the desired separation membrane can be realized.

(ii) a porous coating layer

In addition, the organic / inorganic hybrid separation membrane of the present invention may include a porous coating layer containing a plurality of inorganic particles and a polymeric binder on at least one surface of the porous substrate.

In addition, the porous coating layer includes pores formed by connecting and fixing the inorganic particles by the polymer binder.

The porous coating layer may be suitably formed as a single layer or at least two or more layers by controlling the content of the inorganic particles, the polymer binder, and the process conditions.

 (ii-1) Inorganic particles

The inorganic particles are excellent in affinity for non-aqueous solvents. Thus, the high viscosity solvent penetrates well through the pores formed by the void spaces between the inorganic particles. That is, in the case of a separation membrane including a porous coating layer containing inorganic particles as compared with a separation membrane not including a porous coating layer on a porous substrate, the affinity between the polar substances and the wettability with respect to the high viscosity solvent are further improved by the capillary phenomenon .

The inorganic particles used for forming such a porous coating layer are not particularly limited as long as they are electrochemically stable. Specifically, the inorganic particles have a high dielectric constant and can oxidize and / or oxidize at a working voltage range of the lithium secondary battery (for example, 0 to 5 V based on Li / Li ⁺ Or inorganic particles that do not undergo a reduction reaction can be used.

As described above, when inorganic particles having a high dielectric constant are used, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte can be increased, and the ion conductivity of the electrolyte can be improved.

For the reasons stated above, it is preferable that the inorganic particles include high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Representative examples of such inorganic particles is _{BaTiO 3, BaTiO 3, Pb (} Zr, Ti) O 3 (PZT), Pb 1 - x La x Zr 1 - y Ti y O 3 (PLZT, where, 0 <x <1, SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, MgO, and MgO), Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiC, and mixtures thereof, or a mixture of two or more thereof.

In addition to the inorganic particles, inorganic particles having a lithium ion transferring ability, that is, inorganic particles containing a lithium element but having a function of transferring lithium ions without storing lithium can be further used. Examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O _5, including (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3) (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li ₃ lithium nitride such as _{N (Li x N y, 0} <x <4, 0 <y <2), Li 3 PO 4 SiS 2 family, such as _{-Li 2 S-SiS 2 glass (} Li x Si _{y S z, 0 <x <} 3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 , etc., such as P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7), or a mixture thereof.

The average particle size of the inorganic particles is not limited. However, since the pore size and porosity mainly depend on the size of the inorganic particles, it is preferable that the inorganic particles have a mean particle size of about 0.001 to 10 탆 . If the average particle diameter is less than 0.001 탆, the dispersibility may deteriorate, and if the average particle diameter exceeds 10 탆, the thickness of the porous coating layer may increase.

(ii-2) Polymeric binder

In order to improve mechanical properties such as flexibility and elasticity of the finally formed porous coating layer, the polymer binder contained in the porous coating layer of the present invention preferably has a glass transition temperature (Tg) of -200 Lt; 0 &gt; C to 200 &lt; 0 &gt; C is preferably used.

These polymeric binders act as a binder to bond and stably fix between inorganic particles or between the inorganic particles and the porous substrate. The polymer binder may be a polymer commonly used in the art to form a porous coating layer on a porous substrate. Specifically, a polymer having better heat resistance than the porous substrate may be used.

In addition, the polymer binder does not necessarily have ion conductivity, but the performance of the lithium secondary battery can be further improved when a polymer having ion conductivity is used. Therefore, it is preferable to use a material having a high permittivity constant, which is also possible for a polymeric binder. In fact, since the degree of dissociation of the salt in the electrolyte depends on the permittivity constant of the electrolyte solvent, the higher the permittivity constant of the polymeric binder, the better the salt dissociation in the electrolyte. The permittivity constant of the polymeric binder may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), preferably 10 or more.

In addition to the functions described above, the polymeric binder may be characterized by being capable of exhibiting a high degree of swelling by gelation upon impregnation with a liquid electrolyte. Accordingly, it is preferred that solubility parameter is used to 15 to 45 MPa ^1/2 of a polymer, may be specifically used a polymer having a solubility parameter of 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range . If, or the solubility of the polymer is less than 15 MPa ^1/2, if it exceeds 45 MPa ^1/2, there is impregnation in the liquid electrolyte can be lowered.

It is preferable to use a hydrophilic polymer having a larger number of polar groups than hydrophobic polymers such as polyolefins as a polymer binder satisfying all of these physical properties.

Specifically, examples of the hydrophilic polymer having many polar groups include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, poly (vinylidene fluoride-trichlorethylene) Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyethylene), polyvinylpyrrolidone, oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyano Butyl cellulose, and the like (cyanoethylcellulose), cyanoethyl sucrose (cyanoethylsucrose), pullulan (pullulan), carboxymethyl cellulose (carboxyl methyl cellulose).

In the organic / inorganic hybrid separation membrane of the present invention, the mixing ratio of the inorganic particles constituting the porous coating layer and the polymer binder is, for example, 50:50 to 99: 1 by weight, specifically 70:30 to 95: . At this time, if the content ratio of the inorganic particles is less than 50, the content of the polymer binder is high, so that the pore size and porosity in the porous coating layer can be reduced. Also, when the content ratio of the inorganic particles exceeds 99, the mechanical properties (strength) of the porous coating layer may be weakened because the polymer binder content is too small.

In the organic / inorganic composite separator of the present invention, the pore size and porosity of the porous coating layer are not particularly limited, but the pore size is preferably in the range of 0.001 to 10 μm, and the porosity is preferably in the range of 10 to 90% Do. Since the pore size and porosity mainly depend on the size of the inorganic particles, when the inorganic particles having a particle size of 1 탆 or less are used, the pores formed are also about 1 탆 or less. This pore structure is filled with the non-aqueous electrolyte to be injected at a later time, and the non-aqueous electrolyte filled in this way serves as an ion transfer function. When the pore size and porosity are 0.001 탆 or less and 10% or less, respectively, it can act as a resistive layer. If the pore size and porosity exceed 10 탆 and 90% respectively, mechanical properties may be deteriorated.

In the organic / inorganic composite separator of the present invention, the thickness of the porous coating layer may be 0.01 to 20 탆.

The organic / inorganic hybrid separation membrane of the present invention can be produced by coating a porous substrate with a polymeric binder solution in which inorganic particles are dispersed, and drying the resultant. In this case, the coating method may be a conventional coating method known in the art, for example, a dip coating, a die coating, a roll coating, a comma coating, Various methods can be used. The porous coating layer may be selectively formed on one or both surfaces of the porous substrate.

In addition, the separation membrane according to the present invention may further include other additives for gelation within the scope of not impairing the object of the present invention, in addition to the above-mentioned inorganic particles and polymers as the porous coating layer component.

The separator of the present invention is interposed between the positive electrode and the negative electrode. In the case where the polymer binder is a polymer capable of gelation upon impregnation with a liquid electrolyte, the electrolyte injected after assembling the cell may react with the polymer to gel.

(b) Non-aqueous electrolyte

Further, in the lithium secondary battery of the present invention, the non-aqueous electrolyte includes a lithium salt and a non-aqueous solvent.

Specifically, the non-aqueous electrolyte of the present invention includes a lithium salt having a concentration of 0.8 M to 2 M and a non-aqueous solvent having a viscosity of 1.4 to 50 cP at 25 캜, and a high viscosity non-aqueous electrolyte having a viscosity of 3.5 cP or more at 25 캜 .

(i) a lithium salt

Specifically, if the concentration of the lithium salt contained in the nonaqueous electrolyte solution of the present invention is too low or too high, an optimal point at which the ionic conductivity becomes maximum can be obtained (J. Phys. Chem. B. 2003, page 107) For example, 0.8 to 2 M concentration, specifically 0.8 to 1.4 M concentration.

If the concentration of the lithium salt is less than 0.8 M, not only the ion conductivity of the electrolytic solution is drastically lowered but also the viscosity of the final non-aqueous electrolyte is lowered even when a high viscosity non-aqueous solvent is used as the solvent of the non-aqueous electrolyte. The wettability effect of the separator is reduced, and thus the meaning of using the separator containing the porous coating layer is discolored. If the concentration of the lithium salt is more than 2M, the ionic conductivity of the electrolyte is drastically lowered, and the viscosity of the final nonaqueous electrolyte rapidly increases irrespective of the viscosity of the nonaqueous solvent, so that the wettability effect of the separator is lowered.

The lithium salt may be used, without limitation, those which are commonly used in a lithium secondary battery, and the representative examples include _{LiPF 6, LiBF 4, LiFSI (} Lithium bis (fluorosulfonyl) imide, F 2 NO 4 S 2. Li), LiBETI ( lithium bisperfluoroethanesulfonimide, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiTFSI (lithium bis) trifluoromethanesulfonimide, LiN (CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ Li, LiC (CF ₃ SO ₂ ) ₃ , LiSbF _{6 , LiAsF 6, LiClO 4, LiDFOB} (LiC 2 BO 4 F 2), LiTFOP (LiC 2 PO 4 F 4), LiDFOP (LiC 4 PO 4 F 2), LiDFP (LiPO 2 F 2), LiN (C 2 F ₅ SO ₂ ) ₂ And LiBOB (LiC ₄ BO ₈ ), or a mixture of two or more thereof.

(ii) a non-aqueous solvent

The non-aqueous solvent constituting the non-aqueous electrolyte of the present invention is preferably a high viscosity non-aqueous solvent having a viscosity of at least 1.4 cP at 25 DEG C because it can ultimately improve the safety of the non-aqueous electrolyte.

Specifically, the non-aqueous solvent preferably has a viscosity at 25 ° C of 1.4 to 50 cP, specifically 1.4 to 30 cP, more specifically 1.4 to 4.5 cP.

In fact, since the viscosity of the nonaqueous electrolyte depends on the viscosity of the nonaqueous solvent, the viscosity of the nonaqueous electrolyte can be improved when the viscosity of the nonaqueous solvent is within the range of 1.4 to 50 cP. If the viscosity of the nonaqueous solvent is 50 cP or more, the safety of the nonaqueous electrolyte solution may be improved, but the ionic conductivity of the electrolyte solution and the wettability of the separator membrane are decreased, thereby decreasing the performance of the secondary battery.

The high viscosity non-aqueous solvent contained in the non-aqueous electrolyte of the present invention has a viscosity within the above range, and any high viscosity non-aqueous solvent capable of contributing to the thermal stability of the battery can be used. Typical examples of the highly viscous nonaqueous solvents include ethylene glycol, gamma-butyrolactone, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, cis-2,3-butylene carbonate, trans- , A succinonitrile, an adiponitrile, a fluoroethylene carbonate, or a difluoroethylene carbonate, and an ionic liquid, or a mixed solvent of two or more kinds.

The ionic liquid is a liquid having a very high viscosity and can be used as any ionic liquid that does not burn, volatilize, has a relatively high ionic conductivity, and can contribute to the thermal stability of a lithium secondary battery. Based ionic liquid, a pyridinium ionic liquid, a piperidinium ionic liquid, and a phosphonium ionic liquid, or a mixture of two or more thereof. Specifically, 1-Ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide as shown in the following Table 1 was used as the ionic liquid, imide: EMIm-TFSI (CAS no. 174899-82-2), 1-Ethyl-3-methylimidazorium bis (fluorosulfonyl) imide : EMIm-FSI), 1-methyl-1-propylpiperidinium bis (trifluoromethanesulfonyl) imide: MPPi-TFSI), 1- 1-propylpiperidinium bis (fluorosulfonyl) imide: MPPi-FSI), 1-methyl-1-propylpyrrolidinium bis Methyl-1-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide (1-methyl-1-propyl pyrrolidinium bis (fluorosulfonyl) imide: MPPy-FSI) -methyl-1-propyl &lt; / RTI &gt; pyrrolidinium bis (trifluoromethyl) ethyl-3-methylimidazorium fluorosulfonylamide (EMIFSA), and 1-ethyl-1-butylpiperidinium bis (triphenylphosphine) imide: MPPy-TFSI 1-ethyl-1-butyl piperidinium bis (trifluoromethanesulfonyl) -imide: PP24-TFSI), or a mixed solvent of two or more kinds.

Also, the non-aqueous solvent of the present invention can be prepared by mixing a conventionally used low viscosity non-aqueous solvent such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) Other organic solvents such as a low viscosity organic solvent such as sodium carbonate, sodium carbonate, potassium carbonate, sodium carbonate, sodium carbonate, sodium carbonate, sodium carbonate, sodium carbonate,

At this time, the low viscosity non-aqueous solvent may include up to 10% of the total content of the high viscosity non-aqueous solvent.

In addition, in order to improve the secondary battery performance, compounds such as lactone, ether, ester, acetonitrile, lactam, and ketone may be added to the non-aqueous solvent of the present invention.

The nonaqueous electrolyte solution of the present invention comprising the lithium salt and the nonaqueous solvent as described above is preferably a high viscosity nonaqueous electrolyte solution having a viscosity of not less than 3.5 cP and not more than 60 cP. If the viscosity of the non-aqueous electrolyte is 3.5 cP or less, the stability of the secondary battery may be lowered or the electrolyte salt concentration may be lowered, thereby deteriorating the battery performance. On the contrary, when the viscosity of the nonaqueous electrolyte is higher than 60 cP, the wettability of the separation membrane including the porous coating layer is deteriorated and the performance of the secondary battery deteriorates.

The nonaqueous electrolyte solution of the present invention may be injected at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

As described above, the high viscosity non-aqueous electrolyte of the present invention can be prepared by incorporating a lithium salt having a certain concentration into a non-aqueous solvent having a predetermined viscosity, thereby improving the wettability of the separation membrane containing the porous coating layer, .

(c) anode and cathode

Meanwhile, the electrode (anode and cathode) to be applied together with the separator of the present invention is not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof. The cathode active material may be a conventional cathode active material that can be used for a cathode of a conventional lithium secondary battery. It is preferable to use a lithium composite oxide. As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for a negative electrode of a lithium secondary battery can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable.

Non-limiting examples of the positive current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example

I. Non-aqueous electrolyte  Viscosity change measurement

Ethylene glycol: gamma-butyrolactone was mixed at 2: 3 v / v to prepare a nonaqueous solvent having a viscosity of 1.99 cP at 25 ° C.

Next, the viscosity change of the non-aqueous solvent was measured while adding dimethyl carbonate (DMC) to the non-aqueous solvent at the ratio shown in the following Table 1, and the results are shown in Table 1 below.

Next, 1M LiPF ₆ was added to the nonaqueous solvent to prepare a non-aqueous electrolyte, and then the viscosity change was measured. The results are shown in Table 2 below.

DMC input (g) Viscosity (cP) Before the introduction of LiPF ₆ After the 1M LiPF ₆ charge a 0 1.99 6.49 b One 1.65 5.62 c 2 1.44 4.87 d 3 1.28 4.66 e 4 1.18 3.90 f 5 1.10 3.48 g 6 1.05 3.27 h 7 1.01 3.09 i 8 0.97 2.90-

As shown in Table 2, it was confirmed that the viscosity of the non-aqueous electrolyte increased up to 4.5 cP after the addition of 1M LiPF ₆ (a in Table 2).

II. Non-aqueous electrolyte  Produce

(Production Example 1)

1.0M of LiPF ₆ was dissolved in fluoroethylene carbonate having a viscosity of 4.1 cp at a temperature of 25 ° C to prepare a non-aqueous electrolyte (1) of the present invention having a viscosity of 8.28 cP (see Table 3 below).

(Production Example 2)

Ethylene carbonate: gamma-butyrolactone was mixed at 2: 3 v / v under a temperature condition of 25 占 폚 to prepare a non-aqueous solvent having a viscosity of 2 cP.

Next, 1.5 M LiBF ₄ was added to the nonaqueous solvent to prepare a non-aqueous electrolyte (2) of the present invention having a viscosity of 5.23 cP (see Table 3 below).

(Production Example 3)

A nonaqueous solvent having a viscosity of 1.44 cP was prepared by mixing ethylene carbonate: gamma-butyrolactone: dimethyl carbonate (DMC) at a ratio of 2: 3: 2 v / v under a temperature condition of 25 ° C.

Next, 1.5M LiBF ₄ was added to the nonaqueous solvent to prepare a non-aqueous electrolyte (3) of the present invention having a viscosity of 3.93 cP (see Table 3 below).

(Production Example 4)

(EMIm-TFSI) having a viscosity of 45.9 cP under a temperature condition of 25 ° C was charged with 0.8 M of LiTFSI to obtain a nonaqueous electrolyte solution of the present invention having a viscosity of 52.2 cP at 25 ° C (4) (see Table 3 below).

(Production Example 5)

Ethyl methyl imidazole-trifluoromethanesulfonylamide: dimethyl carbonate (DMC) was mixed at 4: 6 v / v under a temperature condition of 25 ° C to prepare a nonaqueous solvent having a viscosity of 1.94 cP.

Next, 1.5 M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte (5) of the present invention having a viscosity of 5.04 cP (see Table 3 below).

(Production Example 6)

Ethyl methyl imidazole-trifluoromethanesulfonylamide: dimethyl carbonate (DMC) was mixed at 4: 6 v / v under a temperature condition of 25 ° C to prepare a nonaqueous solvent having a viscosity of 1.94 cP.

Next, 0.8M of LiTFSI was added to the non-aqueous solvent to prepare a non-aqueous electrolyte (6) of the present invention having a viscosity of 4.91 cP (see Table 3 below).

(Production Example 7)

A nonaqueous solvent having a viscosity of 1.52 cp was prepared by mixing ethylene carbonate: gamma-butyrolactone: EMC at 2: 3: 2 v / v under a temperature condition of 25 ° C.

Next, 1.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte (7) of the present invention having a viscosity of 4.07 cp (see Table 3 below).

(Preparation Example 8)

Ethylmethyl imidazole-trifluoromethanesulfonylamide: ethyl methyl carbonate (EMC) was mixed at 4: 6 v / v under a temperature condition of 25 ° C to prepare a nonaqueous solvent having a viscosity of 2.08 cP.

Next, 1.5M LiBF ₄ was added to the nonaqueous solvent to prepare a non-aqueous electrolyte (8) of the present invention having a viscosity of 5.2 cP (see Table 3 below).

(Comparative Production Example 1)

Ethylene carbonate: gamma-butyrolactone: dimethyl carbonate (DMC) was mixed at a ratio of 2: 3: 3 v / v under a temperature condition of 25 ° C to prepare a nonaqueous solvent of 1.28 cP.

Next, 1.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 3.15 cP at 25 ° C (see Table 3 below).

(Comparative Production Example 2)

A nonaqueous solvent having a viscosity of 1.44 cP was prepared by mixing ethylene carbonate: gamma-butyrolactone: dimethyl carbonate (DMC) at a ratio of 2: 3: 2 v / v under a temperature condition of 25 ° C.

Next, 0.5M LiBF ₄ was added to the nonaqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 2.07 cP at 25 ° C (see Table 3 below).

(Comparative Production Example 3)

Ethylene carbonate: gamma-butyrolactone: dimethyl carbonate (DMC) was mixed at a ratio of 2: 3: 3 v / v under a temperature condition of 25 ° C to prepare a nonaqueous solvent of 1.28 cP.

Next, 2.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 4.81 cP at 25 ° C (see Table 3 below).

 (Comparative Production Example 4)

A nonaqueous solvent having a viscosity of 1.49 cP was prepared by mixing ethylene carbonate: gamma-butyrolactone: EMC at 2: 3: 3 v / v under a temperature condition of 25 ° C.

Next, 0.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 2.10 cP (see Table 3 below).

(Comparative Production Example 5)

And a non-aqueous solvent having a viscosity of 1.52 cP was prepared by mixing ethylene carbonate: gamma-butyrolactone: EMC at 2: 3: 2 v / v under a temperature condition of 25 ° C.

Then, 0.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 2.13 cP (see Table 3 below).

(Comparative Production Example 6)

A nonaqueous solvent having a viscosity of 1.49 cP was prepared by mixing ethylene carbonate: gamma-butyrolactone: EMC at 2: 3: 3 v / v under a temperature condition of 25 ° C.

Next, 2.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 4.97 cP (see Table 3 below).

(Comparative Production Example 7)

Ethylene carbonate: gamma-butyrolactone was mixed at 2: 3 v / v under a temperature condition of 25 占 폚 to prepare a non-aqueous solvent having a viscosity of 2 cP.

Next, 0.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 2.53 cP (see Table 3 below).

(Comparative Production Example 8)

Ethylene carbonate: gamma-butyrolactone was mixed at 2: 3 v / v under a temperature condition of 25 占 폚 to prepare a non-aqueous solvent having a viscosity of 2 cP.

Next, 2.5M LiBF ₄ was added to the non-aqueous solvent to prepare a non-aqueous electrolyte having a viscosity of 6.02 cP (see Table 3 below).

II. Battery Manufacturing

(Example 1)

a. Membrane manufacturing

Polyvinylidene fluoride-hexafluoropropylene copolymer and cyanoethylpolyvinyl alcohol were added to acetone at 5 weight ratio and 5 weight ratio, respectively, and dissolved at 50 DEG C for 12 hours or longer to prepare a polymer binder solution. Was added thereto over 12 hours, the ball mill method (ball mill) the average particle size of the Al ₂ O ₃ powder by Al ₂ O ₃ powder (:: polymer mixture = 90 10 wt% Al ₂ O ₃ powder) in a polymer binder solution prepared The slurry was pulverized and dispersed at 400 nm to prepare a slurry. The thus-prepared slurry was coated on a polyethylene / polypropylene porous substrate having a thickness of 16 탆 by a dip coating method to prepare an organic / inorganic hybrid membrane including a porous coating layer. At this time, the pore size of the porous substrate was 0.5 μm and the porosity was 58%. Also, the thickness of the porous coating layer was adjusted to about 4 탆 based on one side of the film. The pore size in the porous coating layer was about 0.5 mu m and the porosity was about 58%.

b. Manufacture of batteries

A separator prepared by the above-described method was interposed between a cathode made of LiCoO ₂ and Li (Ni _0.53 Co _0.20 Mn _0.27 ) ₂ O ₂ in an amount of 2: 1 and a cathode made of artificial graphite, and fluoroethylene carbonate Of 4.1 cP), 1.0 M of LiPF ₆ dissolved in a non-aqueous electrolyte (viscosity at 25 was 8.28 cP) And then the coin cell of the present invention was prepared by a general method (see Table 3 below).

(Example 2)

In the same manner as in Example 1, except that an organic / inorganic hybrid separator comprising a polyethylene terephthalate nonwoven fabric base material having a thickness of 12 탆 was used instead of the polyethylene / polypropylene porous material in Example 1, Cells were prepared. The nonwoven fabric used was made of microfine fibers having an average thickness of about 3 탆 and pores having a particle diameter of less than 70 탆 were used in an amount exceeding 50% (see Table 3 below).

(Example 3)

A coin cell of the present invention was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte of Production Example 2 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 4)

A coin cell of the present invention was prepared in the same manner as in Example 2 except that the non-aqueous electrolyte of Production Example 2 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 5)

A coin cell of the present invention was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte of Production Example 3 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 6)

A coin cell of the present invention was prepared in the same manner as in Example 2 except that the non-aqueous electrolyte of Production Example 3 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 7)

A coin cell of the present invention was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte of Production Example 4 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 8)

A coin cell of the present invention was prepared in the same manner as in Example 2 except that the non-aqueous electrolyte of Production Example 4 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 9)

A coin cell of the present invention was produced in the same manner as in Example 1 except that the non-aqueous electrolyte of Production Example 5 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 10)

A coin cell of the present invention was prepared in the same manner as in Example 2 except that the non-aqueous electrolyte of Production Example 6 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 11)

As the cathode active material, LiCoO ₂ 2.5 wt% of Super-P as a conductive material and 2.5 wt% of PVdF as a binder were added to NMP (N-methyl-2-pyrrolidone) to prepare a cathode active material slurry. And pressed to produce a positive electrode.

As the negative electrode active material, artificial graphite 2.5 wt% of Super-P as a conductive material and 2.5 wt% of PVdF as a binder were added to NMP (N-methyl-2-pyrrolidone) to prepare an anode active material slurry, which was coated on one surface of a copper foil And pressed to produce a positive electrode.

An electrode assembly was produced between the positive electrode and the negative electrode through the separation membrane prepared in the step (a) of Example 1, and then the nonaqueous electrolyte solution of Production Example 2 was injected to prepare a circular lithium secondary battery See Table 3 below).

(Example 12)

A coin cell was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte of Production Example 7 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 13)

A coin cell was prepared in the same manner as in Example 2 except that the non-aqueous electrolyte of Production Example 7 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Example 14)

A coin cell was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte of Production Example 8 was used instead of the non-aqueous electrolyte of Production Example 1 (see Table 3 below).

(Comparative Example 1)

A coin cell was prepared in the same manner as in Example 1, except that a polyethylene / polypropylene porous base membrane having a thickness of 16 μm, which did not contain a porous coating layer, was used in place of the organic / inorganic hybrid membrane of Example 1 3).

(Comparative Example 2)

A coin cell was prepared in the same manner as in Example 3, except that a polyethylene / polypropylene porous base membrane having a thickness of 16 μm, which did not contain a porous coating layer, was used in place of the organic / inorganic hybrid separation membrane of Example 3 3).

(Comparative Example 3)

A coin cell was prepared in the same manner as in Example 5, except that a polyethylene / polypropylene porous base membrane having a thickness of 16 μm, which did not contain a porous coating layer, was used in place of the organic / inorganic hybrid membrane of Example 5 3).

(Comparative Example 4)

A coin cell was prepared in the same manner as in Example 7 except that a polyethylene / polypropylene porous base membrane having a thickness of 16 탆, which did not contain a porous coating layer, was used in place of the organic / inorganic hybrid membrane of Example 7 3).

(Comparative Example 5)

A coin cell was prepared in the same manner as in Example 10, except that a polyethylene / polypropylene porous base membrane having a thickness of 16 μm, which did not contain a porous coating layer, was used in place of the organic / inorganic hybrid separation membrane of Example 10 3).

(Comparative Example 6)

A secondary battery was produced in the same manner as in Example 11 except that the nonaqueous electrolyte of Comparative Production Example 1 was used in place of the nonaqueous electrolyte of Production Example 2 (see Table 3 below).

(Comparative Example 7)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 2 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

(Comparative Example 8)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 3 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

(Comparative Example 9)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 4 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

(Comparative Example 10)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 5 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

(Comparative Example 11)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 6 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

(Comparative Example 12)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 7 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

(Comparative Example 11)

A secondary battery was prepared in the same manner as in Comparative Example 6 except that the non-aqueous electrolyte of Comparative Preparation Example 6 was used in place of the non-aqueous electrolyte of Comparative Preparation Example 1 (see Table 3 below).

Experimental Example

Experimental Example  One. Charging and discharging  Evaluation of characteristics (1)

A coin cell of Example 1 using a polyolefin-based porous film as a porous substrate and a coin cell of Example 2 using a polyethylene terephthalate nonwoven fabric as a porous substrate were subjected to CC / CV charging (4.35 V, 1 / 20 C cut), and CV discharge (3.0 V cut) to evaluate charge / discharge characteristics.

As shown in Fig. 1, the coin cell of Example 2 using a polyethylene terephthalate nonwoven fabric as a porous substrate was superior to that of the coin cell of Example 1 using a polyolefin porous film as a porous substrate. It is considered that this is due to the kind of the polymer constituting the nonwoven fabric and the porosity of the nonwoven fabric.

Experimental Example  2. Charging and discharging  Evaluation of characteristics (2)

CC / CV charging (4.35 V, 1 / 20C cut) at 2.5 mA current (0.5 C) was performed on the coin cells of Comparative Examples 1 and 2 using a separation membrane without a porous coating layer and a high viscosity nonaqueous solvent (4.91 cp) Charging and discharging were performed under the condition of CV discharge (3.0 V cut) to evaluate charge-discharge characteristics. The results are shown in Fig. At this time, the measurement method is the same as that of Experimental Example 1 above.

As shown in FIG. 2, it can be seen that the coin cells of Comparative Examples 1 and 2 using a separator without a porous coating layer and a high viscosity non-aqueous solvent (4.91 cp) were unable to charge and discharge.

Experimental Example  3. Charging and discharging  Evaluation of characteristics (3)

The coin cells of Comparative Examples 2 and 3 using the separation membrane without the porous coating layer together with the high viscosity non-aqueous solvent and the coin cells of Examples 3 to 6 and 12 and 13 of the present invention were subjected to a current of 2.5 mA ) Was charged / discharged under conditions of CC / CV charging (4.35V, 1 / 20C cut) and CV discharging (3.0V cut) to evaluate charge / discharge characteristics. The results are shown in Fig.

As shown in FIG. 3, the coin cells of Comparative Examples 2 and 3 using a separator having no porous coating layer together with a high viscosity non-aqueous solvent had a largely poor charge-discharge performance, whereas the organic / inorganic composite The coin cells of Examples 3 to 6 and Examples 12 and 13 using the separator and the high viscosity non-aqueous solvent together show good charge-discharge performance. Particularly, the charge / discharge performance of the coin cell of Example 13 using the polyethylene terephthalate nonwoven fabric as a porous substrate was superior to that of the coin cell of Example 12 using a polyolefin porous film as a porous substrate.

Experimental Example  4. Charging and discharging  Evaluation of characteristics (4)

The coin cells of Examples 7 to 10 using a high viscosity nonaqueous electrolyte solution together with the separator provided with the porous coating layer and the separator without the porous coating layer and the coin cells of Comparative Examples 4 and 5 using the ionic liquid as the non- Charge-discharge characteristics were evaluated by charging / discharging under conditions of CC / CV charging (4.35V, 1 / 20C cut) and CV discharging (3.0V cut) at 2.5mA current (0.5C). The results are shown in Fig.

As shown in FIG. 4, the coin cells of Examples 7 to 10 are confirmed to have better performance than the coin cells of Comparative Examples 4 and 5.

Experimental Example  5. Evaluation of overcharge characteristics

Ten circular lithium secondary batteries prepared in Example 11 and Comparative Examples 6 to 13 were charged to 4.2 V. The charged batteries were overcharged to 10 V with a constant current of 2A. Subsequently, a constant voltage of 18.5 V was maintained for 6 hours to observe occurrence of ignition and explosion, and the results are shown in Table 3 below.

Also, the overcharged circular lithium secondary batteries were put into an oven at 60 DEG C, and the time point at which the battery was short-circuited due to a malfunction of the CID which is the overcharge prevention window was measured. The results are shown in Table 4 below.

Example
11 Comparative Example
6 Comparative Example
7 Comparative Example
8 Comparative Example
9 Comparative Example
10 Comparative Example
11 Comparative Example
12 Comparative Example 13 Ignition / explosion
(Count) 0 Three 5 Three 5 6 2 6 One Non-ignition / non-explosion
(Count) 10 things 7 5 7 5 4 8 4 9 When CID malfunctions > 100 days <15 days <13 days <18 <14 days <13 days <19th <16th <25

Referring to Table 4, in the case of the circular lithium secondary batteries of Comparative Examples 6 to 13, the lithium salt is contained at a low concentration or the high viscosity solvent sufficient to prevent overcharging is insufficient. On the other hand, in the case of the circular secondary cell of Example 11 using the high viscosity non-aqueous solvent according to the present invention, it was found that the safety was excellent, and the explosion was prevented in the overcharging due to the small amount of generated gas even in a high temperature environment, .

Claims (20)

A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte solution in which a lithium salt is dissolved in a nonaqueous solvent,
The separation membrane comprises a porous substrate; And a porous coating layer formed on at least one surface of the porous substrate, wherein the porous coating layer comprises a plurality of inorganic particles, a polymeric binder, and a polymeric binder, the inorganic particles being connected and fixed to each other to form pores &Lt; / RTI &
Wherein the non-aqueous electrolyte is a high viscosity non-aqueous electrolyte containing a lithium salt having a concentration of 0.8 M to 2 M and a non-aqueous solvent having a viscosity of 1.4 to 50 cP and having a viscosity of 3.5 cP or more at 25 ° C.
The method according to claim 1,
Wherein the non-aqueous electrolyte comprises a lithium salt having a concentration of 0.8 M to 2 M and a non-aqueous solvent having a viscosity of 1.4 to 30 cP, and having a viscosity at 25 ° C of 3.5 cP or more and 60 cP or less.
The method according to claim 1,
Wherein the nonaqueous electrolyte solution is a nonaqueous electrolyte solution containing a lithium salt having a concentration of 0.8 M to 1.4 M and a nonaqueous solvent having a viscosity of 1.4 to 4.5 cP and having a viscosity at 25 캜 of 3.5 cP or more and 60 cP or less.
The method according to claim 1,
Wherein the porous substrate comprises a porous film or a porous nonwoven fabric.
The method of claim 4,
Wherein the porous film is a single substance selected from the group consisting of polyethylene, polypropylene, polybutylene, and polypentene, or a mixture of two or more thereof.
The method of claim 4,
The porous nonwoven fabric may be at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyester, polycarbonate, polyimide, polyether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, Is a single substance or a mixture of two or more selected from the group consisting of ethylene, polyvinylidene fluoride, polyvinyl chloride, polyacrylonitrile, cellulose, nylon, polyparaphenylenebenzobisoxazole, polyarylate and glass A lithium secondary battery characterized by.
The method according to claim 1,
Wherein the inorganic particles include inorganic particles in which an oxidation and / or reduction reaction does not occur in an operating voltage range of the lithium secondary battery (for example, 0 to 5 V based on Li / Li ⁺ ).
The method according to claim 1,
Wherein the inorganic particles include high-permittivity inorganic particles having a dielectric constant of 5 or more.
The method according to claim 1,
The inorganic particles are _{BaTiO 3, BaTiO 3, Pb (} Zr, Ti) O 3 (PZT), Pb 1 - x La x Zr 1 - y Ti y O 3 (PLZT, where, 0 <x <1, 0 <y MgO, NiO, CaO, ZnO (MgO), Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , , ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , and SiC, or a mixture of two or more thereof.
The method according to claim 1,
Wherein the polymer binder comprises a polymer having a glass transition temperature (Tg) of -200 to 200 ° C.
The method according to claim 1,
Wherein the polymer binder includes a polymer having a solubility index of 15 to 45 MPa & ^{lt ; 1/2 &} gt ;.
The method according to claim 1,
The polymeric binder may be selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polymethyl methacrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, ethylene vinyl acetate Cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethyl sucrose, fluoran and carboxymethylcellulose as well as cellulose derivatives such as polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, Or a mixture of two or more of them. The lithium secondary battery according to claim 1,
The method according to claim 1,
Wherein the mixing ratio of the inorganic particles: polymer binder is 50:50 to 99: 1 by weight.
The method according to claim 1,
The thickness of the porous substrate is 1 to 100 탆,
Wherein the thickness of the porous coating layer is 0.01 to 20 占 퐉.
The method according to claim 1,
The lithium salt is _{LiPF 6, LiBF 4, LiFSI (} F 2 NO 4 S 2. Li), LiBETI (LiN (C 2 F 5 SO 2) 2), LiTFSI (LiN (CF 3 SO 2) 2), CF 3 _{SO 3 Li, LiC (CF 3} SO 2) 3, LiSbF 6, LiAsF 6, LiClO 4, LiDFOB (LiC 2 BO 4 F 2), LiTFOP (LiC 2 PO 4 F 4), LiDFOP (LiC 4 PO 4 F 2 ), LiDFP (LiPO ₂ F ₂ ), LiN (C ₂ F ₅ SO ₂ ) ₂ and LiBOB (LiC ₄ BO ₈ ), or a mixture of two or more thereof. battery.
The method according to claim 1,
The non-aqueous solvent may be selected from the group consisting of ethylene glycol, gamma-butyrolactone, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, cis-2,3-butylene carbonate, trans- Wherein the lithium ion secondary battery comprises a single substance selected from the group consisting of adiponitrile, fluoroethylene carbonate, or difluoroethylene carbonate, and an ionic liquid, or a mixed solvent of two or more thereof.
18. The method of claim 16,
Wherein the ionic liquid is at least one selected from the group consisting of an imidazolium ionic liquid, an ammonium ionic liquid, a pyrrolidinium ionic liquid, a pyridinium ionic liquid, and a phosphonium ionic liquid, Lithium secondary battery according to claim 1 or 2.
The method according to claim 16 or 17,
Wherein the ionic liquid is selected from the group consisting of 1-ethylmethyl-3-imidazolium bis (trifluoromethanesulfonyl) imide, 1-ethylmethyl-3-imidazolium-bis (fluorosulfonyl) Propylpiperidinium bis (trifluoromethanesulfonyl) imide, 1-methyl-1-propylpiperidinium bis (fluorosulfonyl) imide, 1-methyl- Methyl-1-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide, (1-ethyl-3-methylimidazolium fluorosulfonylamide, And 1-ethyl-1-butylpiperidinium bis (trifluoromethanesulfonyl) -imide, or a mixture of two or more thereof.
The method according to claim 1,
Wherein the non-aqueous solvent further comprises a low-viscosity organic solvent or a cyclic carbonate solvent.
The method of claim 19,
The low-viscosity organic solvent may be a single substance selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, ethyl acetate and propyl acetate, And mixtures thereof. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;

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