KR20140082565A - Cyclotriphosphazene compound, preparing method thereof, electrolyte for lithium secodary battery, and lithium secodary battery including the same - Google Patents

Abstract

A cyclotriphosphazene compound in which at least one fluorine is substituted with a group represented by formula 1 below, a preparing method thereof, an electrolyte for a lithium secondary battery including the cyclotriphosphazene compound, and a lithium secondary battery including the electrolyte are provided. Formula 1 is *A-B-CN, where A is a heteroatom having an unshared electron pair, * represents a combined site of the fluorinated cyclotriphosphazene compound with phosphor (P), and B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms.

Description

TECHNICAL FIELD The present invention relates to a cyclotriphosphazene compound, a method for producing the same, an electrolyte for a lithium secondary battery comprising the cyclotriphosphazene compound, and a lithium secondary battery having the electrolyte.

A cyclotriphosphazene compound, a process for producing the same, an electrolyte for a lithium secondary battery comprising the same, and a lithium secondary battery having the same.

A lithium secondary battery, which has recently been spotlighted as a power source for portable electronic devices, has a discharging voltage twice as high as that of a conventional battery using an aqueous alkaline solution, resulting in a battery exhibiting a high energy density. Such a lithium secondary battery includes a positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium and a negative electrode including a negative active material capable of intercalating and deintercalating lithium And the electrolyte solution is injected into the battery cell.

At present, such a lithium secondary battery is not satisfactory in terms of safety, flame retardancy, and life characteristics, and thus there is much room for improvement.

In one aspect, there is provided a novel cyclotriphosphazene compound and a process for producing the same.

Another aspect of the present invention is to provide an electrolyte for a lithium secondary battery containing the cyclotriphosphazene compound and having improved stability.

Another aspect of the present invention is to provide a lithium secondary battery including the electrolyte and having improved ion conductivity with improved stability.

According to one aspect, there is provided a cyclotriphosphazene compound wherein at least one fluorine of the fluorinated cyclotriphosphazene compound is substituted by a group represented by the following formula (1).

[Chemical Formula 1]

* A-B-CN

Wherein A is a hetero atom having a non-covalent electron pair,

* Represents the region bound to phosphorus (P) of the fluorinated cyclotriphosphazene compound,

And B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms.

According to other aspects

Lithium salts;

Non-aqueous organic solvent; And

There is provided an electrolyte for a lithium secondary battery comprising the above-mentioned cyclotriphosphazene compound.

According to another aspect, an anode; cathode; And a lithium secondary battery including the above-described electrolyte.

According to another aspect, there is provided a process for preparing a cyclotriphosphazene compound which comprises reacting a compound represented by the following formula (6), hexafluorocyclotriphosphazene and a solvent to obtain the above-mentioned cyclotriphosphazene compound / RTI >

[Chemical Formula 6]

AH-B-CN

In the above formula (6), A is a hetero atom having a non-covalent electron pair,

And B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms.

The electrolyte for a lithium secondary battery according to an exemplary embodiment can realize a lithium secondary battery having excellent flame retardance and safety as well as improved charge / discharge and lifetime characteristics.

1 is a schematic view showing a lithium secondary battery according to one embodiment.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

There is provided a cyclotriphosphazene compound wherein at least one fluorine of the fluorinated cyclotriphosphazene compound is substituted by a group represented by the following formula (1).

[Chemical Formula 1]

* A-B-CN

Wherein A is a hetero atom having a non-covalent electron pair,

* Represents the region bound to phosphorus (P) of the fluorinated cyclotriphosphazene compound,

And B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms.

The A may be, for example, nitrogen or oxygen.

The alkylene group having 1 to 5 carbon atoms includes methylene, ethylene, propylene, butylene or pentyl group.

The group represented by the formula (1) is represented by the following formula (1a) or (1b).

[Formula 1a]

Wherein n is an integer of 1 to 5,

[Chemical Formula 1b]

In the formula (1b), n is an integer of 1 to 5,

In the above formulas (1a) and (1b), * represents a region bonded to phosphorus (P) of the fluorinated cyclotriphosphazene compound.

The cyclotriphosphazene compound is a novel compound having a high phosphorus content and excellent reduction resistance. And as the flame retardant additive, an electrolyte for a lithium secondary battery that can prevent thermal runaway of the battery can be manufactured.

The cyclotriphosphazene compound has a P = N group and a C≡N group, and these groups act as a positive electrode additive in order to enhance the oxidation stability of the electrolyte and the negative reaction at the positive electrode interface And the performance and stability of the battery such as suppression of thickness expansion can be improved. It acts on the metal in the electrolyte eluted from the anode to prevent OCV failure. Further, by varying the number of cyano groups in the cyclotriphosphazene compound, the degree of coordination with the cathode active material can be controlled differently.

The cyclotriphosphazene compound is, for example, a compound represented by the following formula (2) or a compound represented by the following formula (3).

(2)

In the general formula (2), n is an integer of 1 to 5.

(3)

In the above formula (3), n is an integer of 1 to 5.

In Formula 2, n is an integer of 1 to 4, for example. In Formula 3, n is an integer of 1 or 2, for example.

According to one embodiment, the cyclotriphosphazene compound is a compound represented by the following formula (4) or a compound represented by the following formula (5).

[Chemical Formula 4]

[Chemical Formula 5]

The cyclotriphosphazene compound can be obtained by reacting a compound represented by the following formula (6), hexafluorocyclotriphosphazene and a solvent.

[Chemical Formula 6]

AH-B-CN

In the above formula (6), A is a hetero atom having a non-covalent electron pair,

And B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms.

In Formula 6, A may be, for example, nitrogen (N) or oxygen (O).

The compound represented by the formula (6) is a compound represented by the following formula (7) or a compound represented by the formula (8).

(7)

Wherein n is an integer of 1 to 5,

[Chemical Formula 8]

In Formula 8, n is an integer of 1 to 5.

The amount of the compound represented by the formula (6) may be 1.0 to 6.1 moles based on 1 mole of hexafluorocyclotriphosphazene. For example, in the case of obtaining the compound represented by the general formula (4) or the compound represented by the general formula (5), the compound represented by the general formula (6) is used in an amount of 1 mole to 1.1 mole based on 1 mole of hexafluorocyclotriphosphazene .

The reaction of the compound represented by Chemical Formula 6 with hexafluorocyclotriphosphazene and a solvent can be carried out, for example, under reflux conditions.

The hexafluorocyclotriphosphazene can be prepared by reacting hexachlorocyclotriphosphazene, sodium fluoride and a solvent.

The content of sodium fluoride is 7.0 to 7.1 mol based on 1 mol of hexachlorocyclotriphosphazene. As the solvent, acetonitrile or the like is used.

And said hexachlorocyclotriphosphazene is ammonium chloride, a contaminant. Can be prepared by reacting zinc chloride and a solvent. The reaction is carried out under reflux conditions.

The solvent is, for example, monochlorobenzene.

The content of zinc chloride is not particularly limited, but is, for example, 0.005 to 0.03 mol based on 1 mol of phosphorus pentachloride.

The content of the ammonium chloride is not particularly limited, but is, for example, 1.0 to 1.1 moles based on 1 mole of phosphorous contamination.

Ammonium chloride, contaminant. The reaction of the zinc chloride and the solvent is carried out at 100 to 150 ° C.

The synthesis of the compound represented by the formula (4) and the compound represented by the formula (5), which is a cyclotriphosphazene compound according to one embodiment, is as follows.

As shown in Reaction Scheme 1 below, it can be easily synthesized through a three-step reaction step using phosphorus chloride and ammonium chloride as starting materials.

[Reaction Scheme 1]

In Scheme 1, n is 2, Et ₂ O is ether, CH ₃ CN is acetonitrile, and MCB is monochlorobenzene.

Unless otherwise specified herein, "substituted" means that at least one hydrogen atom is replaced by a halogen atom, a hydroxy group, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C1 to C20 alkoxy group, A C3 to C30 cycloalkynyl group, a C2 to C30 heterocycloalkyl group, a C2 to C30 heterocycloalkenyl group, a C2 to C30 heterocycloalkynyl group, a C6 to C30 aryl group, a C6 to C30 aryl (Wherein R 'and R "are the same or different from each other and are a hydrogen atom, a C1 to C20 alkyl group or a C6 to C30 aryl group), an ester group (C2 to C30 heteroaryl group, (-COOR '' ', wherein R' '' is a small atom, a C1 to C20 alkyl group or a C6 to C30 aryl group), a carboxyl group (-COOH), a nitro group (-NO2) or a cyano group (-CN) .

The electrolyte for a lithium secondary battery according to an embodiment includes a lithium salt, a non-aqueous organic solvent, and the above-mentioned cyclotriphosphazene compound.

When the cyclotriphosphazene compound is used for an electrolyte, the battery has excellent safety in overcharging, and is excellent in conductivity and lifetime.

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 the basic lithium secondary battery, and a material that promotes the movement of lithium ions between the positive electrode and the negative electrode to be.

The lithium salt Specific examples include _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiCF 3 SO 3, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiN (SO 3 C 2 F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) wherein x and y are natural numbers, have.

The concentration of the lithium salt can be used within the range of about 0.1M to about 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and can effectively transfer lithium ions.

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 compound, an ester compound, an ether compound, a ketone compound, an alcohol compound, an aprotic solvent or a combination thereof may be used.

As the carbonate compound, a chain carbonate compound, a cyclic carbonate compound, or a combination thereof may be used.

The chain carbonate compound may be selected from the group consisting of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropylcarbonate , EPC), methylethyl carbonate (MEC), or a combination thereof. The cyclic carbonate compound may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate , BC), fluoroethylene carbonate (FEC), vinylethylene carbonate (VEC), or a combination thereof.

The carbonate compound may be used in an amount of more than about 60% by weight of the chain carbonate compound and less than about 40% by weight of the cyclic carbonate compound. When used within the above ratio range, it can be made from a solvent having a high viscosity and a low dielectric constant.

Examples of the ester compound include methyl acetate, acetate, n-propyl acetate, dimethylacetate, methyl propionate, ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone mevalonolactone, caprolactone, and the like may be used. Examples of the ether compound include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran and the like. As the ketone compound, cyclohexanone and the like may be used . Examples of the alcohol-based compound include ethyl alcohol, isopropyl alcohol, and the like.

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

The electrolyte may further include succinonitrile as an additive. The succinonitrile may be contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total weight of the electrolyte, and specifically 0.5 to 3 parts by weight. When the succinonitrile is further added to the electrolyte, the succinonitrile bonds with the transition metal of the cathode active material at the cathode interface, thereby suppressing the failure of OCV at the time of conversion and improving the stability at a high temperature such as heat exposure.

The electrolyte may further include 1,3-propane sultone as an additive. The 1,3-propane sultone may be contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the electrolyte. When the 1,3-propane sultone is further added to the electrolyte, charging / discharging and cycling characteristics are improved.

Hereinafter, a lithium secondary battery including the electrolyte will be described with reference to FIG.

1 is a schematic view showing a lithium secondary battery according to one embodiment.

1, a lithium secondary battery 3 according to an embodiment includes a positive electrode 5, a negative electrode 6, and a separator 7 positioned between the positive electrode 5 and the negative electrode 6 The electrode assembly 4 is a prismatic type battery which is located in the battery case 8 and contains an electrolyte injected into the upper part of the case and is sealed with the cap plate 11. [ Of course, the lithium secondary battery according to one embodiment is not limited to the prismatic shape, and any shape such as a cylindrical shape, a coin shape, and a pouch shape may be used as long as it includes an electrolyte for a lithium secondary battery according to an embodiment and can operate as a battery. Of course.

The electrolyte includes an electrolyte according to an embodiment of the present invention. The electrolyte is, for example, a liquid electrolyte.

The anode 5 includes a current collector and a cathode active material layer formed on the current collector. The cathode active material layer includes a cathode active material, a binder, and optionally a conductive agent.

Al (aluminum) may be used as the current collector, but the present invention is not limited thereto. 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 cobalt, manganese, nickel, or a composite oxide of a metal and lithium in combination thereof, and specific examples thereof include compounds represented by any one of the following formulas:

Li _a A _{1 - b} B _b D ₂ wherein, in the formula, 0.90? A? 1.8, and 0? B? 0.5; Li _a E _{1 -b} B _b O _{2 -c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05; LiE (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) 2 -b BbO 4-c D c; Li _a Ni _{1 -b- c} Co _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _{2 -?} F _? Wherein? 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? _{Li a Ni 1 - bc Co b} B c O 2 -α F 2 ( wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2 a); Li _a Ni _{1 -b- c} Mn _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1 -b- c} Mn _b B _c O _{2 - ?} F _{? Wherein} , in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2; 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 G _e O 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 wherein, in the above formula, 0.90? A? 1.8, and 0.001? B? 0.1; Li _a MnG _b O ₂ (in the above formula, 0.90? A? 1.8, 0.001? B? 0.1); Li _a Mn ₂ GbO 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 ; LiIO 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; B 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; F 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; I is Cr, V, Fe, Sc, Y or a combination thereof; J may be 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 at least one coating element compound selected from the group consisting of oxides, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. 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 process can be carried out by using the above-mentioned compounds in the above-mentioned compound so that the physical properties of the cathode active material are not adversely affected (for example, if it can be coated by spray coating,

And it can be understood by those who are engaged in the field, so a detailed explanation will be omitted.

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. Specific examples thereof include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, But are not limited to, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- , Acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but are not limited thereto.

The conductive agent 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 agent include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as Ketjen black, carbon fiber, copper, nickel, aluminum and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used singly or in combination.

The negative electrode 6 includes a current collector and a negative electrode active material layer formed on the current collector.

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, but is not limited thereto.

The negative electrode active material layer includes a negative electrode active material, a binder, and optionally a conductive agent.

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 the material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material generally used in lithium secondary batteries can be used as the carbonaceous material, and typical examples thereof include crystalline carbon, Amorphous carbon or any 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.

As the lithium metal alloy, a lithium-metal alloy may be selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, An alloy of a selected metal may be used.

As the material capable of doping and dedoping lithium, Si, SiOx (0 <x <2), Si-Y alloy (Y is an alkali metal, an alkaline earth metal, a Group 13 to Group 16 element, a transition metal, And a combination thereof.

(Wherein Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 to Group 16 element, a transition metal, a rare earth element, and a combination thereof, Sn), and the like, and at least one of them may be mixed with SiO2. The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Se, Te, Po, and combinations thereof.

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

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Examples of the binder include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, 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 agent 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 agent include natural graphite, artificial graphite, carbon black, acetylene black, Carbon-based materials such as Ketjen black and carbon fiber; 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 positive electrode 5 and the negative electrode 6 are prepared by mixing an active material, a conductive agent 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 separator 7 may be a single film or a multilayer film, and may be made of, for example, polyethylene, polypropylene, polyvinylidene fluoride or a combination thereof.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto. In addition, contents not described here can be inferred sufficiently technically if they are skilled in the art, and a description thereof will be omitted.

Manufacturing example  1: Cyclotriphosphazene  Synthesis of compounds

1) Preparation of hexachlorocyclotriphosphazene A

[Reaction Scheme 2]

                                                      A

A three neck round-bottomed flask equipped with a reflux condenser, a magnetic stirrer bar and a temperature controller was charged with phosphorus pentachloride (PCl ₅ , 1 eq), ammonium chloride (ammonium chloride (NH ₄ Cl, 1.1 eq), zinc chloride (ZnCl ₂ , 0.015 eq) and monochlorobenzene (MCB) were added.

The reaction temperature was gradually raised to 130 DEG C over 3 hours while stirring the reaction mixture, and the mixture was stirred at this temperature for 2 hours.

When the reaction was completed, the reaction mixture was cooled to room temperature, filtered under reduced pressure, and the solvent was removed under reduced pressure to obtain a crude product. The crude product was purified by column chromatography to obtain hexachlorocyclotriphosphazene A.

2) Preparation of hexafluorocyclotriphosphazene B

[Reaction Scheme 3]

      A B

Hexachlorocyclo-triphosphazene A (1 eq), sodium fluoride (7 eq) and acetonitrile were added to a one-necked round bottom flask equipped with a magnetic stirrer, and when the reaction was completed Lt; / RTI &gt; at room temperature.

When the reaction was complete, the reaction mixture was filtered and the solvent was removed under reduced pressure. The resultant was purified by column chromatography to obtain hexafluorocyclotriphosphazene B.

_{^{19 F-NMR (CDCl 3)}} -68.24, -68.48, -69.82, -70.03;

FT-IR (neat) 120, 1100, 950, 800, 750

3) Preparation of cyclotriphosphazene compound of formula (4)

[Reaction Scheme 4]

  B Formula 4

A 1 neck round-bottomed flask was charged with hexafluorocyclotriphosphazene B (2 eq), 3-hydroxypropionitrile (1 eq) and monoglyme ) 2.5 mol%, sodium carbonate (1.1 eq) and diethyl ether were added and stirred. The reaction mixture was stirred overnight at ambient temperature until the reaction was complete.

The reaction mixture was filtered and the solvent was removed under reduced pressure. The resultant product was purified by flash column chromatography to obtain a cyclotriphosphazene compound of formula (4).

The structure of the cyclotriphosphazene compound of Formula 4 obtained according to Preparation Example 1 was confirmed by NMR spectroscopy and NMR spectroscopy.

_{^{1 H-NMR (CDCl 3)}} 2.85 (2H), 4.05 (2H);

_{^{13 C-NMR (CDCl 3)}} 19.39, 63.11, 115.31;

¹⁹ F-NMR (CDCl ₃ ) -65.28, -67.55, -69.17, -69.85, -70.13;

FT-IR (neat) 1500, 1270, 970, 820

Manufacturing example  2: Cyclotriphosphazene  Synthesis of compounds

[Reaction Scheme 5]

   B Formula 5

Hexafluorocyclotriphosphazene B (1 eq) obtained according to Preparation Example 1 and diethyl ether (1 eq) obtained according to Preparation Example 1 were placed in a three-neck round bottom flask equipped with a reflux condenser, a magnetic stirrer bar and a temperature controller And 3,3'-iminodipropionitrile (1 eq) in ether was slowly added dropwise to the ether for 1 hour.

After the completion of the reaction, the reaction mixture was cooled to room temperature, the solvent was removed under reduced pressure, and the residue was purified by column chromatography to obtain the cyclo To obtain a triphosphazene compound.

The structure of the cyclotriphosphazene compound of Chemical Formula 5 obtained in Preparation Example 2 was confirmed by NMR spectroscopy and IR spectroscopic data.

Example  1-3: Electrolyte Manufacturing

, Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a weight ratio of 3: 5: 2, respectively, in an amount of 5 parts by weight based on 100 parts by weight of a polypropylene resin, 6 parts by weight of a fluoroethylene carbonate (FEC), 0.5 part by weight of vinylethylene carbonate a mixed solution of 0.9M LiPF ₆ concentration of 0.2 and ₄ parts by weight were dissolved LiBF, succinonitrile, 3 parts by weight, 1,3-propane sultone (1,3-pROPANE sULTONE) 2.5 parts by weight Preparation example 1 Was added according to the kind and content shown in Table 1 below to prepare an electrolyte.

Example  4-6: Electrolyte Manufacturing

Except that the cyclotriphosphazene compound of Chemical Formula 5 obtained in Production Example 2 was used instead of the cyclotriphosphazene compound of Chemical Formula 4 obtained in Preparation Example 1, Electrolyte was prepared.

division Content of cyclotriphosphazene compound ^* (parts by weight) Example 1 5 Example 2 10 Example 3 15 Example 4 5 Example 5 10 Example 6 15

* Based on 100 parts by weight of electrolyte.

Comparative Example  1-3: Electrolyte Manufacturing

Except that the dimethylaminocyclotriphosphazene compound represented by the following formula (9) was used in place of the cyclotriphosphazene compound of the formula (4), respectively, to prepare an electrolyte.

[Chemical Formula 9]

Comparative Example  4: Electrolyte Manufacturing

An electrolyte was prepared in the same manner as in Example 1 except that the cyclotriphosphazene compound (4) was not added.

Comparative Example  5-7: Preparation of electrolyte

1 part by weight of succinonitrile, and 1 part by weight of 1,3-propane sultone (1,3-propane sultone) were used to prepare electrolytes.

Comparative Example  8: Preparation of electrolyte

An electrolyte was prepared in the same manner as in Comparative Example 5, except that the dimethylaminocyclotriphosphazene compound represented by the formula (9) was not added.

Production Example  1: Manufacture of lithium secondary battery

LiCoO ₂ as a cathode active material, polyvinylidene fluoride (PVDF) as a binder, and carbon as a conductive agent were mixed at a weight ratio of 92: 4: 4, respectively, and dispersed in N-methyl-2-pyrrolidone to prepare a cathode active material layer composition . The positive electrode active material layer composition was coated on an aluminum foil having a thickness of 20 탆 and dried and rolled to prepare a positive electrode.

Crystalline artificial graphite as a negative electrode active material and polyvinylidene fluoride (PVDF) as a binder were mixed at a weight ratio of 92: 8, respectively, and dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode active material layer composition. The negative electrode active material layer composition was coated on a copper foil having a thickness of 15 탆 and dried and rolled to prepare a negative electrode.

The prepared positive electrode and negative electrode were wound and compressed using a separator made of polyethylene having a thickness of 25 占 퐉 and inserted into a square (2050 mA) can of 51 mm x 51 mm x 61 mm to prepare a lithium secondary battery. In this case, the electrolyte of Example 1 was used as the electrolyte.

Production Example  2-6: Lithium secondary battery production

A lithium secondary battery was produced in the same manner as in Production Example 1, except that the electrolyte of Example 2-6 was used instead of the electrolyte of Example 1, respectively.

Comparative Production Example  1-8: Lithium secondary battery production

A lithium secondary battery was produced in the same manner as in Production Example 1 except that the electrolyte of Comparative Example 1-8 was used in place of the electrolyte of Example 1, respectively.

Evaluation example  1: Lithium secondary battery Heat exposure  evaluation

Each of the lithium secondary batteries manufactured in accordance with Production Examples 1 to 6 and Comparative Production Examples 1 to 8 was fabricated in the following manner. I) After a rated charging (1025 mA / 4.35 V, cut-off 102 mA) , Ii) after raising the temperature to 5 ° C / min until reaching 150 ° C, holding it at the cell temperature of 150 ° C for 60 minutes, and iii) observing the OCV, The safety of exposure was evaluated, and the results are shown in Table 2 below.

Evaluation example  2: Through test of lithium secondary battery

Each of the lithium secondary batteries manufactured in accordance with Production Examples 1 to 6 and Comparative Production Examples 1 to 8 was fabricated in the following manner. I) After a rated charging (1025 mA / 4.35 V, cut-off 102 mA) Iii) after passing through the cell at the center of the cell at a speed of 150 mm / s, and observing the appearance and appearance of the cell, the penetration stability was evaluated. The results are shown in Table 2 below.

The safety evaluation criteria in the evaluation examples 1 and 2 are as follows.

The number before L means the number of test cells,

L0: good, L1: leakage, L2: flash, L3: smoke, L4: ignition, and L5: rupture.

division Thermal exposure test Penetration test Production Example 1 3L1 3L1 Production Example 2 3L1 3L1 Production Example 3 3L1 3L1 Production Example 4 3L1 3L1 Production Example 5 3L1 3L1 Production Example 6 3L1 3L1 Comparative Production Example 1 3L1 3L1 Comparative Production Example 2 3L1 3L1 Comparative Production Example 3 3L1 3L1 Comparative Production Example 4 2L1, 1L4 - Comparative Production Example 5 3L4 3L1 Comparative Production Example 6 3L4 3L1 Comparative Production Example 7 3L4 3L1 Comparative Production Example 8 3L4 1L1, 2L4

Referring to Table 2, the lithium secondary battery of Production Example 1-6 had the same thermal exposure test and penetration test results as those of Comparative Production Examples 1-3, but the lithium secondary battery of Production Example 1-6 It is confirmed that the event time at which the heat exposure of the first embodiment is performed is delayed compared with the case of Comparative Production Example 1-3. Therefore, it was found that the lithium secondary battery of Production Example 1-6 has improved safety and flame retardancy as compared with Comparative Production Examples 1-3.

In addition, the lithium secondary battery of Production Example 1-6 had improved heat exposure characteristics as compared with Comparative Production Examples 4-8. As a result of the penetration test, it was confirmed that the safety of the lithium secondary battery of Production Example 1-6 was improved as compared with Comparative Production Example 8. [

Evaluation example  3: Lithium secondary battery Semi-penetrating  Test

Three lithium rechargeable batteries were manufactured in accordance with Production Examples 1 to 3 and Comparative Production Example 9, and charged with constant current-constant voltage (CC-CV) (1025 mA / 4.35 V, cut-off 102 mA) (CC) discharge (500mA, cut-off 3.3V) after a rest period within 72 hours or more. The central portion of the cell of the battery was semi-penetrated at a rate of 10 mm / s, and the generation phenomenon and the appearance thereof were observed to evaluate the penetration stability. The results are shown in Table 2 below.

The safety evaluation criteria in the evaluation example 3 are as follows.

The number before L means the number of cells corresponding to the evaluation criterion described later,

L0: Good, L1: Leaking, L2: Smoke (<200 ^o C), L3: Smoke (> 200 ^o C), L4: Ignition, and L5: Rupture.

division Semi-penetration test Production Example 1 3L1 Production Example 2 3L1 Production Example 3 3L1 Comparative Production Example 4 2L1, L4

Referring to Table 3, it was found that the lithium secondary battery of Production Example 1-3 was improved as a result of the penetration test as compared with Comparative Production Example 4. [ From these results, it can be seen that the safety of the lithium secondary battery of Production Example 1-3 is improved as compared with Comparative Production Example 4. [

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

3: lithium secondary battery 5: anode
6: cathode 7: separator
8: Battery case 11: Cap plate

Claims (15)

At least one fluorine of the fluorinated cyclotriphosphazene compound,
A cyclotriphosphazene compound substituted by a group represented by the following formula (1): &lt; EMI ID =
[Chemical Formula 1]
* AB-CN
Wherein A is a hetero atom having a non-covalent electron pair,
* Represents the region bound to phosphorus (P) of the fluorinated cyclotriphosphazene compound,
And B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms. The method according to claim 1,
The cyclotriphosphazene compound represented by the general formula (1) is represented by the following general formula (1a) or (1b)
[Formula 1a]

Wherein n is an integer of 1 to 5,
[Chemical Formula 1b]

In the formula (1b), n is an integer of 1 to 5,
In the above formulas (1a) and (1b), * represents a region bonded to phosphorus (P) of the fluorinated cyclotriphosphazene compound. The method according to claim 1,
Wherein the cyclotriphosphazene compound is a compound represented by the following formula 2 or a compound represented by the following formula 3:
(2)

Wherein n is an integer of 1 to 5,
(3)

In the above formula (3), n is an integer of 1 to 5. The method of claim 3,
In Formula 2, n is 1, 2, 3 or 4,
Wherein n is 1 or 2 in the formula (3). The method according to claim 1,
Wherein the cyclotriphosphazene compound is a compound represented by the following formula (4) or a compound represented by the following formula (5).
[Chemical Formula 4]

[Chemical Formula 5]

Lithium salts;
Non-aqueous organic solvent; And
An electrolyte for a lithium secondary battery comprising the cyclotriphosphazene compound of any one of claims 1 to 5. The method according to claim 6,
Wherein the content of the cyclotriphosphazene compound is 0.5 to 10 parts by weight based on 100 parts by weight of the total weight of the electrolyte. The method according to claim 6,
The lithium salt is _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiCF 3 SO 3, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiN (SO 3 C 2 F 5 ) ₂ , LiC ₄ F ₉ SO ₃ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers) Electrolyte for lithium secondary battery. anode;
cathode; And
A lithium secondary battery comprising the electrolyte according to claim 6. 10. The method of claim 9,
Wherein the content of the cyclotriphosphazene compound is 0.5 to 10 parts by weight based on 100 parts by weight of the total weight of the electrolyte. 10. The method of claim 9,
The lithium salt
_{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiCF 3 SO 3, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiN (SO 3 C 2 F 5) 2, LiC ₄ F ₉ SO ₃ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) wherein x and y are natural numbers, or a combination thereof. A process for producing a cyclotriphosphazene compound, which comprises reacting a compound represented by the following formula (6) and hexafluorocyclotriphosphazene and a solvent to obtain the cyclotriphosphazene compound of any one of claims 1 to 5 &Lt; / RTI &gt;
[Chemical Formula 6]
AH-B-CN
In the above formula (6), A is a hetero atom having a non-covalent electron pair,
And B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms. 13. The method of claim 12,
Wherein the compound represented by the formula (6) is a compound represented by the following formula (7) or a compound represented by the following formula (8).
(7)

Wherein n is an integer of 1 to 5,
[Chemical Formula 8]

In Formula 8, n is an integer of 1 to 5. 13. The method of claim 12,
Wherein the hexafluorocyclotriphosphazene is obtained by reacting a cyclotriphosphazene, sodium fluoride and a solvent. 15. The method of claim 14,
Wherein the hexachlorocyclotriphosphazene is obtained by reacting ammonium chloride, phosphorus pentachloride, zinc chloride and a solvent.

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