KR20140008233A - Separator for rechargeable lithium battery and rechargeable lithium battery including the same - Google Patents

Abstract

The present invention relates to a separator for rechargeable lithium battery and a rechargeable lithium battery including the same. According to the embodiment of the present invention, the separator for rechargeable lithium battery includes a phase transition material of which phase transition temperature of changing insulator into conductor is 67-75 °C. The phase transition material is tungsten vanadium oxide (VO2).

Description

A separator for a lithium secondary battery and a lithium secondary battery including the same {SEPARATOR FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME}

The present invention relates to a separator for a lithium secondary battery and a lithium secondary battery including the same.

At present, the IT industry technology continues to make rapid progress compared to other science and technology fields, and many products are being developed around portable and easy mobile devices such as laptops, mobile phones, and PDAs. For such IT mobile devices, miniaturization, weight reduction, and large capacity of batteries, which are energy sources, are essential, and lithium secondary batteries are currently being used and researched.

Lithium secondary batteries are the most widely used batteries because of their high energy density per unit volume. However, in lithium secondary batteries, when the temperature inside the battery rises, the battery swells and explodes at about 150 ° C. This explosion has long been known, but there is no countermeasure. Therefore, there is a need for measures for preventing or delaying such an explosion.

One embodiment of the present invention is to provide a separator for a lithium secondary battery that can prevent and delay the explosion risk of the lithium secondary battery.

Another embodiment of the present invention is to provide a lithium secondary battery including the separator.

One embodiment of the present invention provides a separator for a lithium secondary battery including a phase change material having a phase transition temperature of 67 to 75 ° C., which changes from an insulator to a conductor.

The phase change material may be tungsten doped vanadium oxide (VO ₂ ).

The tungsten-doped vanadium oxide (VO ₂ ) may be doped with tungsten at 10 to 20% by weight based on the total amount of the tungsten-doped vanadium oxide (VO ₂ ).

Another embodiment of the present invention is a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; The separator positioned between the anode and the cathode; And it provides a lithium secondary battery comprising an electrolyte solution impregnated with the positive electrode, the negative electrode and the separator.

Another embodiment of the present invention is a porous substrate; A first phase transition region located on one surface of the porous substrate; And a second phase transition region located on the other side of the porous substrate, wherein the first phase transition region and the second phase transition region are symmetrically positioned with the porous substrate therebetween, and the first phase transition region and the The second phase transition region provides a separator for a lithium secondary battery comprising a phase change material that changes from an insulator to a conductor above a phase transition temperature.

The pores of the porous substrate may include a phase change material at a position between the first phase transition region and the second phase transition region.

The first phase transition region and the second phase transition region may be connected to each other through the porous substrate to form an integrated phase transition region.

An area of the first phase transition region or the second phase transition region may be 10% or less of one surface area of the porous substrate, and specifically 5% to 10% of one surface area of the porous substrate.

The first phase transition region or the second phase transition region may be positioned as a coating layer on one surface or the other surface of the porous substrate.

The coating layer may have a thickness of 5 to 10 ㎛.

The phase transition temperature may be 67 to 75 ℃.

The phase change material may be tungsten doped vanadium oxide (VO ₂ ).

The tungsten-doped vanadium oxide (VO ₂ ) may be doped with tungsten at 10 to 20% by weight based on the total amount of the tungsten-doped vanadium oxide (VO ₂ ).

Another embodiment of the present invention is a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; The separator positioned between the anode and the cathode; And it provides a lithium secondary battery comprising an electrolyte solution impregnated with the positive electrode, the negative electrode and the separator.

The first phase transition region of the separator may be in contact with the cathode, and the second phase transition region of the separator may be in contact with the anode.

The separator may be formed to prevent or delay the explosion of the lithium secondary battery when the lithium secondary battery is overheated.

Other details of the embodiments of the present invention are included in the following detailed description.

The separator may prevent and delay an explosion when the lithium secondary battery is overheated.

1 is a cross-sectional view showing a cross section of a separator according to an embodiment.
2 is a diagram illustrating one surface of a separator according to another exemplary embodiment.
3 is a cross-sectional view illustrating a cross section of a separator according to another embodiment.
4 is a cross-sectional view illustrating a cross section of a separator according to another embodiment.
5 is a view schematically showing a lithium secondary battery structure according to one embodiment.
6 is a schematic cross-sectional view of a rechargeable lithium battery according to another embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

The present invention may be embodied in many different forms and is described with reference to the drawings as necessary and is not limited to the embodiments described herein. Since the size and thickness of each component shown in the drawings of the present specification are arbitrarily shown for convenience of description, the present invention is not necessarily limited to the illustrated.

The separator for a rechargeable lithium battery according to one embodiment may include a phase change material.

The phase change material refers to a material that changes from an insulator to a conductor above a predetermined temperature. The temperature at which the phase change material changes from an insulator to a conductor is called a phase transition temperature.

If the temperature rises excessively during operation of the lithium secondary battery, the battery may explode. Since the phase change material changes to a conductor at or above the phase transition temperature, the separator including the phase change material may be energized, and as a result, the separator may generate a short between the cathode and the anode above the phase transition temperature. By doing so, it is possible to further stop the operation of the battery and thereby prevent or at least delay the explosion of the battery by preventing further temperature rise.

The phase change material may be tungsten doped vanadium oxide (VO ₂ ).

Vanadium oxide (VO ₂ ) is a typical phase change material having an insulating property of about 10 ⁵ Ω below about 67 ° C., and having a resistance of about 10 to about 10 ⁻² Ω of the conductor above about 67 ° C. Doping tungsten (W) to vanadium oxide may control the phase transition temperature of about 67 ℃. For example, the phase change material of tungsten doped vanadium oxide may have a phase transition temperature of about 67 to about 75 ° C.

The phase transition temperature may be adjusted by changing the doping content of tungsten. For example, the tungsten-doped vanadium oxide (VO ₂ ) may be doped with tungsten at 10 to 20 wt% based on the total amount of the tungsten-doped vanadium oxide (VO ₂ ).

The phase change material of tungsten-doped vanadium oxide may be prepared without limitation according to known methods by sputtering, ion plating, e-beam deposition, and the like.

For example, a method of preparing the phase change material of the tungsten-doped vanadium oxide by the sputtering method will be described in detail. The laser is irradiated with a single vanadium raw material or two vanadium raw materials and a tungsten raw material in the chamber so that tungsten (W) and vanadium (V) particles are deposited on the substrate. The separator may be manufactured by using the substrate as a porous substrate to be described later. At this time, the process conditions should be the conditions under which the phase change material can be formed, so that it is possible to generate VO ₂ , which is not a phase change material, but V ₂ O ₅ . For example, it is carried out in a mixed gas atmosphere of Ar and O _{2 in} the chamber, where the mixing ratio, temperature and pressure conditions of Ar and O ₂ gas are VO ₂ It is an important condition of production. The condition at this time is Ar: O ₂ in chamber. = 99: 1 to 98: 2, temperature 350 to 400 ° C., and pressure 8 to 12 mTorr.

In general, the separator is formed of a substrate including pores, and the separator may allow the phase change material to be present in the pores. Above the phase transition temperature, the separator may be connected to the phase-transfer materials present in the pores can be energized.

The content of the phase change material included in the separator may be included only to the extent that the current can be supplied above the phase transition temperature.

In another embodiment of the present invention, a separator including a porous substrate, a first phase transition region located on one surface of the porous substrate, and a second phase transition region located on the other surface of the porous substrate is provided.

The first phase transition region and the second phase transition region are located at two-sided symmetric positions with the porous substrate therebetween. The first phase transition region and the second phase transition region include a phase change material, and the phase change material is a material that phase-transfers from an insulator to a conductor above the phase transition temperature as described above.

1 is a cross-sectional view showing a cross section of a separator according to an embodiment.

Referring to FIG. 1, the separator 10 includes a porous substrate 11, and first phase transition regions 12 and 12 ′ are formed on one surface of the porous substrate 11. In addition, second phase transition regions 13 and 13 ′ are formed on the other surface of the porous substrate 11.

The first phase transition regions 12 and 12 'and the second phase transition regions 13 and 13' are symmetrically formed with the porous substrate 11 interposed therebetween. Arrows A, B, C and D in the separator 10 indicate the same phase (height), respectively, and the first phase transition regions 12 and 12 'and the second phase transition regions 13 and 13' It shows a structure formed in a symmetrical phase.

For example, the first phase transition regions 12 and 12 'and the second phase transition regions 13 and 13' may be formed by coating or patterning a portion of the surface of the porous substrate 11 with a phase change material, respectively. have. In one embodiment, a pattern for coating or patterning the phase change material on the surface of the porous substrate to form the phase change material covers a negatively patterned plate, and the aforementioned sputtering method, ion plating method, e The separator may be manufactured by depositing tungsten (W) doped vanadium oxide (VO ₂ ) directly by an e-beam deposition method.

The thickness of the coating layer or pattern formed from the phase change material is also not particularly limited. For example, the coating thicknesses of the first phase transition region and the second phase transition region may be about 5 μm to about 10 μm.

2 is a diagram illustrating one surface of a separator according to another exemplary embodiment. In detail, FIG. 2 illustrates one surface of the separator 10 'manufactured by patterning one surface of the porous substrate 11 with a phase change material to form first phase transition regions 12 and 12'.

The other surface of the separator 10 'may be patterned with a phase change material in the same shape to form second phase transition regions 13 and 13'. In FIG. 2, the phase change region is formed by patterning the phase change material in a stripe shape, but as described above, the pattern shape of the phase change region is not limited.

When the separators 10 and 10 'are overheated during operation of a lithium secondary battery, phase change materials included in the first phase transition regions 12 and 12' and the second phase transition regions 13 and 13 'are formed on the porous substrate 11. The first phase transition region 12 and the second phase transition region 13, and the first phase transition region 12 ′ and the second phase transition region 13 ′ are respectively porous. Through the phase change material penetrating into the pores of the base material 11, it is possible to conduct electricity at a phase transition temperature or higher, thereby inducing a short.

The separator 10, 10 ′ has a structure including two pairs of the first phase transition regions 12 and 12 ′ and the second phase transition regions 13 and 13 ′, but a pair of the first phase transition regions ( The combination of 12) and the second phase transition region 13, or only one of the other pair of the first phase transition region 12 'and the second phase transition region 13' may be present. In addition, the method may further include a combination of an additional first phase transition region and a second phase transition region.

3 is a cross-sectional view illustrating a cross section of a separator according to another embodiment. Referring to FIG. 3, in the separator 20, a phase change material included in the first phase transition regions 22 and 22 ′ and the second phase transition regions 23 and 23 ′ is overheated by a lithium secondary battery. It may include porous substrate regions 24, 24 ′ that penetrate into the pores of 21 to include phase change material in the pores.

4 is a cross-sectional view illustrating a cross section of a separator according to another embodiment.

Referring to FIG. 4, the separator 30 may connect the first phase transition region and the second phase transition region through the porous substrate 31 to form an integrated phase transition region 35, 35 ′. .

The area of the first phase transition region or the second phase transition region may be such that an electric current can be supplied at or above the phase transition temperature, and may be so large that it does not interfere with the separator function as a Li ion channel. For example, an area of the first phase transition region or the second phase transition region may be 10% or less of one surface area of the porous substrate, and specifically 5% to 10%.

The first phase transition region or the second phase transition region may be located on one surface or the other surface of the porous substrate in the form of a coating layer. At this time, the coating layer may have a thickness of 5 to 10 ㎛.

Detailed description of the phase change material is as described above.

In another embodiment, a lithium secondary battery including a cathode including a cathode active material, an anode including an anode active material, and the above-mentioned separator is provided.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and the electrolytic solution used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted. Since the separator has improved binding strength by using a coating layer containing a binder polymer, in particular, in a pouch-type battery in which a flexible packaging material such as a laminate film is used, the separator is more stably bound between the electrode and the separator, thereby resulting in a gap between the electrode and the separator. It can prevent occurrence and fix the position of the separator

5 is a view schematically showing a lithium secondary battery structure according to one embodiment.

Referring to FIG. 5, the lithium secondary battery 100 has a cylindrical shape, a negative electrode 112, a positive electrode 114, a separator 113 disposed between the negative electrode 112 and the positive electrode 114, and the negative electrode 112. ), The electrolyte 114 (not shown) impregnated in the positive electrode 114 and the separator 113, the battery container 120, and the sealing member 140 which encloses the said battery container 120 are comprised as a main part. The lithium secondary battery 100 is constructed by laminating a cathode 112, a separator 113 and an anode 114 in this order and then winding them in a spiral wound state in the battery container 120.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the lithium metal alloy include lithium and a metal such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Q alloy (Q is an alkali metal, an alkaline earth metal, A transition metal, a rare earth element or a combination thereof and not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, A rare earth element or a combination thereof, but not Sn). The specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The anode includes a current collector and a cathode active material layer formed on the current collector.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, it is possible to use at least one of complex oxides of cobalt, manganese, nickel or a combination of metals and lithium, and specific examples thereof include compounds represented by any one of the following formulas. Li _a A _{1 - b} R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _{1 - b} R _b O _{2 - c} D _c , wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05; LiE _{2 - b} R _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -bc} Co _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 - b - c} Co _b R _c O _{2 - ?} Z _{? Wherein} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z _{? Where the} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1; Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise, as a coating element compound, an oxide, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

The cathode active material layer also includes a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

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

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

The electrolytic solution includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate , Ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, An amide such as nitriles such as dimethylformamide, and dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to about 1: 9, the performance of the electrolytic solution may be excellent.

The non-aqueous organic solvent may further include the aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1: 1 to about 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (1).

[Formula 1]

In Formula 1, R ₁ to R ₆ are each independently hydrogen, halogen, a C1 to C10 alkyl group, a C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon-based organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3- , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 - triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 - trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotol Ene, 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, or may be a combination thereof.

The non-aqueous electrolytic solution may further contain vinylene carbonate or an ethylene carbonate compound of the following formula (2) to improve battery life.

(2)

Wherein R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group, and at least one of R ₇ and R ₈ Is a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include, for example, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, . When the vinylene carbonate or the ethylene carbonate compound is further used, the amount of the vinylene carbonate or the ethylene carbonate compound can be appropriately controlled to improve the life.

The lithium salt is dissolved in the non-aqueous organic solvent to act as a source of lithium ions in the battery to enable operation of a basic lithium secondary battery, and a material capable of promoting the movement of lithium ions between the positive electrode and the negative electrode to be. Representative examples of the lithium salt are LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y +1} SO ₂ ), where x and y are natural numbers, LiCl, LiI, LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) borate (LiBOB) or combinations thereof The lithium salt concentration is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is in the above range, the electrolyte has an appropriate conductivity and viscosity. It can exhibit excellent electrolyte performance, and lithium ions can move effectively.

The separator 113 separates the cathode 112 and the anode 114 and provides a passage for moving lithium ions, as described above.

6 is a schematic cross-sectional view of a rechargeable lithium battery according to another embodiment.

The lithium secondary battery 200 includes the above-described separator 213, wherein the first phase transition region of the separator 213 is in contact with the negative electrode 212, and the second phase transition region of the separator 213 is The anode 214 may be in contact. In addition, the lithium secondary battery 200 may include phase transition regions 205 and 205 ′ formed by connecting the first phase transition region and the second phase transition region to each other.

Hereinafter, examples of the present invention will be described. The following embodiments are only examples of the present invention, and the present invention is not limited to the following embodiments.

Example  1 and 2

A separator was prepared by depositing tungsten-doped vanadium oxide, which is a phase change material, in a stripe pattern as shown in FIG. 2 by sputtering (used equipment: Excimer laser, laser type: KrF (248 nm)) on both surfaces of a polyethylene substrate.

Deposition conditions are as follows.

Laser intensity: 4J / ㎠

Repetition rate: 8 Hz

Distance between source and substrate: 8.5 cm

Volume ratio of atmosphere in the chamber Ar: O ₂ = 99: 1 (Example 1) / Ar: O ₂ = 98: 2 (Example 2)

Deposition Pressure: 10mTorr

Substrate Temperature: 400 ℃

Deposition time: 12.5 min

The separator for a lithium secondary battery according to an embodiment may use a phase change material having a phase transition temperature of 67 to 75 ° C. that changes from an insulator to a conductor, thereby preventing or delaying the explosion of the lithium secondary battery when the lithium secondary battery is overheated.

In addition, the separator for a lithium secondary battery according to another embodiment may include a porous substrate, a first phase transition region located on one surface of the porous substrate, and a second phase transition region located on the other surface of the porous substrate. The first phase transition region and the second phase transition region may be symmetrically positioned with the porous substrate interposed therebetween, and the first phase transition region and the second phase transition region are phase transitions that change from an insulator to a conductor at or above a phase transition temperature. By including a material, it is possible to prevent or delay the explosion of the lithium secondary battery when the lithium secondary battery is overheated.

10, 10 ', 20, 30: separator
11, 21, 31: porous substrate
12, 12 ', 22, 22': first phase transition region
13, 13 ', 23, 23': second phase transition region
24, 24 ': porous substrate region
35, 35 ', 205, 205': phase transition region
100, 200: lithium secondary battery
112, 212: cathode
113, 213: Separator
114, 214: anode
120: Battery container
140: sealing member

Claims (17)

Phase transition material with a phase transition temperature of 67 to 75 ° C, changing from insulator to conductor
Separator for a lithium secondary battery comprising a.
The method of claim 1,
The phase change material is tungsten doped vanadium oxide (VO ₂ ) separator for a lithium secondary battery.
3. The method of claim 2,
The tungsten-doped vanadium oxide (VO ₂ ) is a tungsten-doped vanadium oxide (VO ₂ ) is doped at 10 to 20% by weight relative to the total amount of the tungsten-doped vanadium oxide (VO ₂ ) separator.
A cathode comprising a cathode active material;
A negative electrode comprising a negative electrode active material;
The separator of any one of Claims 1-3 located between the said anode and said cathode; And
Electrolyte impregnating the positive electrode, the negative electrode and the separator
&Lt; / RTI &gt;
A porous substrate;
A first phase transition region located on one surface of the porous substrate; And
Second phase transition region located on the other side of the porous substrate
/ RTI &gt;
The first phase transition region and the second phase transition region are located symmetrically with each other with the porous substrate therebetween,
And the first phase transition region and the second phase transition region include a phase change material that changes from an insulator to a conductor at or above a phase transition temperature.
The method of claim 5,
The pores of the porous substrate includes a phase change material at a position between the first phase transition region and the second phase transition region.
The method of claim 5,
And the first phase transition region and the second phase transition region are connected to each other through the porous substrate to form an integrated phase transition region.
The method of claim 5,
A separator for a lithium secondary battery, wherein an area of the first phase transition region or the second phase transition region is 10% or less of one surface area of the porous substrate.
9. The method of claim 8,
The area of the first phase transition region or the second phase transition region is 5% to 10% of the surface area of the porous substrate separator for a lithium secondary battery.
The method of claim 5,
The first phase transition region or the second phase transition region is a separator for a lithium secondary battery is located on one surface or the other surface of the porous substrate as a coating layer.
The method of claim 10,
The coating layer is a lithium secondary battery separator having a thickness of 5 to 10 ㎛.
The method of claim 5,
The phase transition temperature is a separator for a lithium secondary battery of 67 to 75 ℃.
The method of claim 5,
The phase change material is tungsten doped vanadium oxide (VO ₂ ) separator for a lithium secondary battery.
The method of claim 13,
The tungsten-doped vanadium oxide (VO ₂ ) is a tungsten-doped vanadium oxide (VO ₂ ) is doped at 10 to 20% by weight relative to the total amount of the tungsten-doped vanadium oxide (VO ₂ ) separator.
A cathode comprising a cathode active material;
A negative electrode comprising a negative electrode active material;
The separator of any one of Claims 5-14 located between the said anode and said cathode; And
Electrolyte impregnating the positive electrode, the negative electrode and the separator
&Lt; / RTI &gt;
16. The method of claim 15,
The first phase transition region of the separator is in contact with the cathode,
The second phase transition region of the separator is in contact with the anode
Lithium secondary battery.
16. The method of claim 15,
The separator is configured to prevent or delay the explosion of the lithium secondary battery when the lithium secondary battery overheats.

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