KR20180026325A - Electrolyte for lithium secondary battery and lithium secondary battery including the electrolyte - Google Patents

Abstract

Provided are an electrolyte for lithium secondary batteries, and a lithium secondary battery including the same. The electrolyte contains a compound represented by chemical formula 1, a lithium salt, and an organic solvent, wherein the content of the compound represented by chemical formula 1 is less than 3 wt% based on the total weight of the electrolyte. In the chemical formula 1, R_1 to R_15 are independently hydrogen, fluorine, an alkyl group of 1-10 carbon atoms, or an aryl group of 6-10 carbon atoms.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrolyte for a lithium secondary battery, and a lithium secondary battery including the electrolyte.

An electrolyte for a lithium secondary battery, and a lithium secondary battery comprising the same.

As the electric, electronic, communication and computer industries rapidly develop, demand for high performance and high safety secondary batteries is rapidly increasing. In particular, secondary batteries, which are core components, are required to be light in weight and small in size in accordance with the trend of small size and portable use of electric and electronic products. In addition, the necessity of a new type of energy supply source due to environmental pollution problems such as air pollution and noise due to massive supply of automobiles and oil depletion, and the need for development of electric vehicles capable of solving the problems have been increased. It is required to develop a battery having high output and high energy density. In response to this demand, one of the next-generation high-performance new-type high-performance batteries, which are receiving the most attention in recent years, is a lithium secondary battery.

In order to produce lithium secondary batteries having high-density characteristics, a cathode active material having a high nickel content and excellent capacity characteristics is used. However, such a cathode active material is required to be improved since the surface characteristics after cell operation are not sufficiently stable. There is a high need for the development of an electrolyte capable of improving the stability of the above-described cathode active material.

One aspect is to provide an electrolyte for a lithium secondary battery improved in capacity and lifetime characteristics.

Another aspect is to provide a lithium secondary battery having improved cell performance including the electrolyte described above.

On one side

A compound represented by Formula 1 below; Lithium salts; And an organic solvent,

Wherein the content of the compound represented by the formula (1) is less than 3.0% by weight based on the total weight of the electrolyte.

[Chemical Formula 1]

In the formula (1), R ₁ to R ₁₅ independently represent hydrogen, fluorine, a C1-C10 alkyl group, or a C6-C10 aryl group.

The electrolyte further includes at least one selected from vinylene carbonate, vinylethylene carbonate, maleic anhydride and succinic anhydride.

According to another aspect,

anode;

cathode; And

And a reaction product of the electrolyte and the electrolyte disposed between the electrolyte and the electrolyte.

When the electrolyte for a lithium secondary battery according to an embodiment is used, a lithium secondary battery having improved capacity and life characteristics can be manufactured.

FIG. 1 illustrates a structure of a lithium secondary battery according to an embodiment.

Hereinafter, an electrolyte for a lithium secondary battery and a lithium secondary battery including the same according to exemplary embodiments will be described in more detail.

An electrolyte for a lithium secondary battery according to an embodiment includes a compound represented by the following Formula 1: Lithium salts; And an organic solvent,

The content of the compound represented by the formula (1) is less than 3.0% by weight, for example, 0.1 to 2.9% by weight, specifically 0.1 to 2.4% by weight based on the total weight of the electrolyte.

[Chemical Formula 1]

In the formula (1), R ₁ to R ₁₅ independently represent hydrogen, fluorine, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C6-C10 aryl group.

The electrolyte further includes at least one selected from vinylene carbonate, vinylethylene carbonate, maleic anhydride and succinic anhydride.

When a nickel rich nickel-based composite oxide having a high nickel content is used as a cathode active material for a lithium secondary battery, a lithium secondary battery having high output and high capacity can be produced. However, the nickel-rich lithium-nickel composite oxide is unstable in its surface structure after the operation of the battery, leading to further elution of transition metals such as nickel, thereby deteriorating the high temperature lifetime characteristics of the lithium secondary battery comprising the nickel-rich lithium-nickel composite oxide .

Accordingly, the present inventors have solved the above problems and provide an electrolyte excellent in stabilizing the surface of the nickel-rich lithium-nickel composite oxide.

The compound represented by the formula (1) is a compound represented by the following formula (2).

(2)

In the general formula (2), R ₃ , R ₈ and R ₁₃ independently represent hydrogen, fluorine or a methyl group.

R ₃ , R ₈ and R ₁₃ are, for example, all fluorine, hydrogen or a methyl group.

The compound of formula (1) has strong affinity for Ni ^{3 +} at the anode surface. Therefore, Ni is preferentially adsorbed to the Ni on the surface of the anode to protect the surface Ni of the anode. Specifically, there is an effect of preventing the elution of Ni from the surface of the anode or stabilizing the destabilization due to the change of the Ni atom on the surface of the anode.

The compound represented by the formula (1) includes at least one selected from the compounds represented by the following formulas (3) to (6), (6a) and (6b)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

[Chemical Formula 6a]

[Formula 6b]

The content of at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, maleic anhydride and succinic anhydride is 0.1 to 2% by weight, for example, 0.4 to 1.5% by weight, based on the total weight of the electrolyte. When the content of at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, maleic anhydride and succinic anhydride is within the above range, the life and resistance suppressing effect of the lithium secondary battery is excellent.

The electrolyte may contain maleic anhydride. Here, the content of maleic anhydride is 0.1 to 2% by weight, for example, 0.4 to 1.5% by weight.

The electrolyte may further comprise fluoroethylene carbonate. The content of the fluoroethylene carbonate may be 0.5 to 10% by volume or less based on the total volume of the organic solvent. For example, the electrolyte may contain the FEC in an amount of 0.5% by volume or more and 8% by volume or less based on the total volume of the nonaqueous solvent. For example, the electrolyte may contain the FEC in an amount of 1 % by volume or more and 7% by volume or less based on the total volume of the organic solvent.

The organic solvent may be at least one selected from a carbonate-based solvent, an ester-based solvent, an ether-based solvent, and a ketone-based solvent.

Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) EC), propylene carbonate (PC), butylene carbonate (BC), and the like can be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, butyl acetate, methyl propionate, ethyl propionate Decanoate, valerolactone, mevalonolactone, caprolactone, and the like may be used as the active ingredient. 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 organic solvent, for example, tetraethylene glycol dimethyl ether (TEGDME) or the like may be used.

The organic solvent according to one embodiment contains, for example, 50 to 95% by volume of chain carbonate and 5 to 50% by volume of cyclic carbonate.

Wherein the chain carbonate is at least one selected from the group consisting of ethyl methyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC) and dipropyl carbonate The cyclic carbonate is at least one selected from the group consisting of ethylene carbonate, propylene carbonate and butylene carbonate.

The content of the compound represented by the formula (1) is, for example, 0.5 to 2% by weight based on the total weight of the electrolyte.

When the electrolyte according to one embodiment is used, the surface stabilization effect of the nickel-rich lithium-nickel composite oxide is excellent. This surface stabilization effect can be confirmed by preserving the nickel-rich lithium-nickel composite oxide at a high temperature in an anode or by eluting Ni amount after a high-temperature cycle. More specifically, when the electrolyte according to one embodiment is used, the surface Ni is stabilized and the Ni elution amount in the electrolyte becomes smaller than that in the case where the electrolyte is not used after high temperature preservation or high temperature cycle.

The use of an electrolyte having the above-described characteristics not only improves the lifetime at a high temperature of the lithium secondary battery, but also improves the resistance increase suppressing effect.

The electrolyte includes a disulfone-based compound represented by the following formula (7).

(7)

In Formula (7), R ₁ and R ₂ are independently a substituted or unsubstituted C ₁ -C ₃₀ alkylene group, and the substituent of the substituted C ₁ -C ₃₀ alkylene group is halogen, methyl, ethyl, n-propyl (Propenyl) group, a propenyl group, a butenyl group, a butenyl group, an isopropyl group, an n-butyl group, a sec- butenyl) group.

In the present specification, the substituent in the "substituted alkyl group, substituted aryl group, substituted alkylene group" includes a halogen atom, a C1-C20 alkyl group substituted with a halogen atom (eg, CCF ₃ , CHCF ₂ , CH ₂ F, CCl ₃ , , A C 1 -C 20 alkoxy, a C 2 -C 20 alkoxyalkyl, a hydroxy group, a nitro group, a cyano group, an amino group, an amidino group, a hydrazine, a hydrazone, a carboxyl group or a salt thereof, a sulfonyl group, a sulfamoyl group, C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C6-C20 aryl, C6-C20 arylalkyl, C6- C20 heteroaryl group, C7-C20 heteroarylalkyl group, C6-C20 heteroaryloxy group, C6-C20 heteroaryloxyalkyl group and C6-C20 heteroarylalkyl group.

The disulfone compound is at least one selected from compounds represented by the following formula (7a), for example.

[Formula 7a]

The content of the disulfide compound is 0.1 to 5% by weight based on the total weight of the electrolyte. When the content of the disulfide-based compound is in the above range, the life improving effect of the lithium secondary battery is more excellent.

The disulfone-based compound may be, for example, a compound represented by the following formula (15).

[Chemical Formula 15]

The disulfone-based compound has a cyclic structure containing two sulfonyl groups. When such a compound is added to the electrolyte, sulfonate (-SO ₃ -) based polymer film is formed by reduction decomposition first of other components of the electrolyte due to the sulfonyl group and stable at a high temperature due to the cyclic structure. Such a polymer film can cover a wider electrode area, and further, the sulfonate polymer film has excellent stability at a high temperature. Therefore, it is possible to exhibit a strong resistance increase inhibiting effect at a high temperature.

The concentration of the lithium salt in the electrolyte according to an embodiment may be 0.1 to 5.0 M, for example, 0.1 to 2.0 M. However, the concentration is not necessarily limited to this range, and an appropriate concentration may be used if necessary. Further improved battery characteristics within the above range of concentration can be obtained.

The lithium salt _{LiPF 6, LiBF 4, LiCF 3} SO 3, Li (CF 3 SO 2) 2 N, [Li (FSO 2) 2 N, LiC 4 F 9 SO 3, LiN (SO 2 CF 2 CF 3) ₂ , and the compounds represented by the general formulas (8) to (11).

[Chemical Formula 8] [Chemical Formula 9]

 [Chemical formula 10]       (11)

According to one embodiment, the lithium salt is, for example, LiDFOB or LiPF ₆ represented by the general formula (10). The lithium salt may be 1 to 2 M in the electrolyte.

The above-described anode according to another aspect; cathode; And a reaction product of the electrolyte and the electrolyte disposed between the electrolyte and the electrolyte.

As used herein, the term " reaction product of an electrolyte " means a product obtained by the reaction of the electrolyte itself during or after operation of the lithium secondary battery, or a product obtained by reacting the electrolyte with other components of the battery or the like.

The positive electrode comprises a nickel-rich lithium nickel complex oxide having a nickel content of 70 to 95 mol%, for example 80 to 93 mol%, based on the total molar amount of the transition metal.

The nickel-rich lithium-nickel composite oxide may be, for example, a compound represented by the following formula (14).

[Chemical Formula 14]

_{Li a Ni x Co y Mn z} M c O 2 - b A b

1, 0? Z? 1, 0? C <1, x + y + z + c = 1, 0? B? 0.2 ,

M is at least one element selected from the group consisting of vanadium V, magnesium Mg, gallium Ga, silicon Si, tungsten W, molybdenum Mo, iron Fe, chromium Cr, copper Cu, ), Titanium (Ti), aluminum (Al) and boron (B)

A is an element of F, S, Cl, Br or a combination thereof.

The positive electrode compound represented by the formula (14) is, for example, a compound represented by the following formula (14a) or (14b).

[Chemical Formula 14a]

LiNi _x Co _y Mn _z O ₂

 [Chemical Formula 14b]

LiNi _x Co _y Al _z O ₂

In the above formulas (14a) and (14b), 0.8? X? 0.95, 0 <y? 0.2, 0 <z? 0.1.

The nickel-rich lithium nickel composite oxide for example LiNi _{0. 7} Co _{0 . 2} Mn _{0 . 1} O ₂ , LiNi _0.8 Co _0.15 Mn _0.05 O ₂ , LiNi _{0 . 8} Co _{0 . 1} Mn _{0 . 1} O ₂ , LiNi _{0 . 88} Co _{0 . 1} Mn _{0 . 02} O ₂ , LiNi _{0 . 8} Co _{0 . 15} Al _{0 . 05} O ₂ , LiNi _0.7 Co _0.1 Mn _0.2 O _2, or LiNi _{0 . 88} Co _{0 . 1} Al _{0 . 02} O ₂ .

The negative electrode may be at least one selected from the group consisting of a silicon compound, a carbonaceous material, a composite of a silicon compound and a carbonaceous material, and a silicon oxide (SiO _x (0 <x <2), wherein the carbonaceous material includes graphite and the like.

The lithium secondary battery including the electrolyte has a direct current internal resistance (DCIR) rate of increase of 165% or less, for example, 105 to 160% after 300 cycles of charging and discharging at 45 ° C.

The electrolyte according to one embodiment is selected from the group consisting of i) tri (4-fluorophenyl) phosphine, triphenylphosphine, tri (4-methylphenyl) phosphine, tris (2,4-difluorophenyl) Fluoroethylene carbonate, ethylmethyl carbonate, dimethyl carbonate and vinylene carbonate, or ii) at least one member selected from the group consisting of tri (4-fluorophenyl) phosphine, triphenylphosphine At least one member selected from the group consisting of tri (4-methylphenyl) phosphine, tris (2,4-difluorophenyl) phosphine and tris (pentafluorophenyl) phosphine, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and vinyl And may include a carbonate or carbonate.

The electrolyte can be at least one selected from, for example, tri (4-fluorophenyl) phosphine, triphenylphosphine and tri (4-methylphenyl) phosphine, ethylene carbonate, fluoroethylene carbonate, ethylmethyl carbonate, dimethyl carbonate and vinyl The content of tri (4-fluorophenyl) phosphine is 0.5 to 1.5% by weight based on the total weight of the electrolyte, and the mixing volume ratio of ethylene carbonate, fluoroethylene carbonate, ethylmethyl carbonate and dimethyl carbonate is 7: 7: 46: 40, and the content of vinylene carbonate is 0.5 to 1.5% by weight based on the total weight of the electrolyte.

In an electrolyte according to an embodiment, the mixing ratio of the organic solvent, for example, ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate is 20:40:40.

The mixing volume ratio of ethylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in the electrolyte according to another embodiment is, for example, 17: 3: 40: 40.

The electrolyte may further comprise at least one selected from tri (4-fluorophenyl) phosphine, triphenylphosphine and tri (4-methylphenyl) phosphine, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and vinylene carbonate . The content of tri (4-fluorophenyl) phosphine is 0.5 to 1.5% by weight based on the total weight of the electrolyte, the mixing volume ratio of ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate is 20:40:40, The content is 0.5 to 1.5% by weight based on the total weight of the electrolyte.

The shape of the lithium secondary battery is not particularly limited and includes a lithium ion battery, a lithium ion polymer battery, a lithium sulfur battery, and the like.

The lithium secondary battery according to one embodiment can be manufactured by the following method.

First, the anode is prepared.

For example, a cathode active material composition in which a cathode active material, a conductive agent, a binder and a solvent are mixed is prepared. The positive electrode active material composition is coated directly on the positive electrode collector to produce a positive electrode. Alternatively, the cathode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on the metal current collector to produce a cathode. The anode is not limited to those described above, but may be in a form other than the above.

The cathode active material may include a common lithium-containing metal oxide in addition to the nickel-rich lithium-nickel composite oxide described above. As the lithium-containing metal oxide, for example, two or more kinds of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used.

The cathode active material is, for example, Li _a A _{1 - b} B _b D ₂ (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 where} 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05; LiE _{2 - b} B _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; 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, 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 ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1 -bc} 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 -b- c} Mn _b B _c O _{2 - ?} F ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 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 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 G _b O ₄ wherein, 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); In the formula of LiFePO ₄ it may be a compound represented by any one:

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 combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

For example, LiCoO ₂ , LiMn _x O _2x (x = 1 or 2), LiNi _{1 - x} Mn _x O _2x (0 <x <1), LiNi _{1 -xy} Co _x Mn _y O ₂ 0.5, 0≤y≤0.5, a 1-xy> 0.5), LiFePO 4 or the like.

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 an oxide, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a coating element compound of the hydroxycarbonate of the 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 any coating method as long as it can coat the above compound by a method that does not adversely affect physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

The conductive agent is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black; Conductive fibers such as carbon fiber and metal fiber; Carbon fluoride; Metal powders such as aluminum and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And conductive polymers such as polyphenylene derivatives can be used.

The content of the conductive agent is 1 to 20% by weight based on the total weight of the cathode active material composition.

The binder is a component that assists in binding of the active material and the conductive agent and bonding of the active material to the current collector, and is usually added in an amount of 1 to 30 wt% based on the total weight of the cathode active material composition. Examples of such binders include polyvinylidene fluoride (PVdF), polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethylcellulose (CMC) But are not limited to, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, polystyrene, polymethylmethacrylate, polyaniline, acrylonitrile butadiene styrene, phenol resin, epoxy resin, polyethylene terephthalate , Polytetrafluoroethylene, polyphenylene sulfide, polyamideimide, polyetherimide, polyether sulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-diene terpolymer ), Sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, various copolymers and the like.

As the solvent, N-methylpyrrolidone, acetone, water or the like may be used, but not limited thereto, and any solvent which can be used in the technical field can be used. The content of the solvent is, for example, 10 to 100 parts by weight based on 100 parts by weight of the positive electrode active material. When the content of the solvent is within the above range, it is easy to form the active material layer.

The content of the positive electrode active material, the conductive agent, the binder and the solvent is a level commonly used in a lithium secondary battery. Depending on the application and configuration of the lithium secondary battery, one or more of the conductive agent, the binder, and the solvent may be omitted.

For example, N-methylpyrrolidone (NMP) may be used as a solvent, PVdF or PVdF copolymer may be used as a binder, and carbon black or acetylene black may be used as a conductive agent. For example, 94% by weight of the positive electrode active material, 3% by weight of the binder and 3% by weight of the conductive agent were mixed in powder form, NMP was added thereto so as to have a solid content of 70% by weight, The anode can be rolled.

The cathode current collector generally has a thickness of 3 mu m to 50 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The loading level of the prepared cathode active material composition is 30 mg / cm ² or more, for example, 35 mg / cm ² or more, specifically 40 mg / cm ² or more. The electrode density is 3 g / cc or more, for example, 3.5 g / cc or more. For energy density-intensive designs, a loading level of 35 mg / cm ² to 50 mg / cm ² or less and a density of 3.5 g / cc to 4.2 g / cc or less is preferred. For example, it may be a double-sided coated plate with a loading level of 37 mg / cc and a density of 3.6 g / cc.

When the loading level of the cathode active material composition and the range of the electrode density are satisfied, the cell including such a cathode active material can exhibit a high cell energy density of 500 wh / L or more. In the lithium secondary battery, the DCIR (direct current internal resistance) increase rate after charging and discharging at 45 ° C is 165% or less.

Next, the cathode is prepared.

For example, a negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive agent, a binder and a solvent. The negative electrode active material composition is coated directly on the negative electrode collector and dried to produce a negative electrode. Alternatively, the negative electrode active material composition may be cast on a separate support, and then the film peeled off from the support may be laminated on the metal current collector to produce a negative electrode plate.

The negative electrode active material may be, for example, a silicon compound, a silicon oxide (SiO _x (0 <x <2), a composite of a silicon compound and a carbonaceous material. , For example from 10 to 150 nm. The term size refers to the average particle size when the silicone particles are spherical and to the average long axis length when the particles are non-spherical.

When the size of the silicon particles is within the above range, the life characteristics are excellent, and when the electrolyte according to one embodiment is used, the lifetime of the lithium secondary battery is further improved.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in the form of non-shaped, flake, flake, spherical or fiber, and the amorphous carbon may be a soft carbon (soft carbon) Or hard carbon, mesophase pitch carbonization products, fired cokes, and the like.

The composite of the silicon-based compound and the carbon-based material may be, for example, a composite having a structure in which silicon particles are disposed on the graphite surface, or a composite in which silicon particles are contained in and on the graphite surface. The composite may be prepared by dispersing Si particles having an average particle size of about 200 nm or less, for example, 100 to 200 nm, specifically 150 nm, on graphite particles, and then carbon-coating the active material or silicon (Si) The active material is present. Such a composite is available under the trade name SCN1 (Si particle on Graphite) or SCN2 (Si particle inside as w as a on graphite). SCN1 is a carbon-coated active material obtained by dispersing Si particles having an average particle size of about 150 nm on graphite particles. And SCN2 is an active material in which Si particles having an average particle size of about 150 nm are present on and in the graphite.

The negative electrode active material may be used together with the negative electrode active material as long as it can be used as a negative electrode active material of a lithium secondary battery in the related art. (For example, Y is an alkali metal, an alkaline earth metal, a Group 13 to Group 16 element, a transition metal, a transition metal oxide rare earth element, or a mixture thereof) of Si, Sn, Al, Ge, Pb, Bi, Sb, And Y is an alkali metal, an alkaline earth metal, an element of group 13 to group 16, a transition metal, a rare earth element or a combination element thereof, and is not Sn), and the like. 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, Ge, P, As, Sb, Bi, Te, Po, or a combination thereof.

For example, the negative electrode active material may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like.

The conductive agent and the binder in the negative electrode active material composition may be the same as those in the positive electrode active material composition.

However, in the negative electrode active material composition, water may be used as a solvent. For example, when water is used as a solvent, and carboxymethyl cellulose (CMC) - styrene butadiene rubber (SBR), acrylate polymer, or methacrylate polymer is used as a binder, and carbon black, acetylene black, You can use zero.

The content of the negative electrode active material, the conductive agent, the binder and the solvent is a level commonly used in a lithium secondary battery. Depending on the application and configuration of the lithium secondary battery, one or more of the conductive agent, the binder, and the solvent may be omitted.

For example, after mixing 94 wt% of the negative electrode active material, 3 wt% of the binder and 3 wt% of the conductive material in powder form, water is added so that the solid content is about 70 wt%, slurry is formed, , And rolled into a negative electrode plate.

The negative electrode current collector is generally made to have a thickness of 3 mu m to 50 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The loading level of the negative electrode active material composition is set according to the loading level of the positive electrode active material composition. Cm ² or more, for example, 15 mg / cm ² or more, depending on the capacity per g of the negative electrode active material composition. The cathode density can be 1.5 g / cc or more, for example, 1.6 g / cc or more. As a design with an emphasis on energy density, a negative electrode density of 1.65 g / cc or more and 1.9 g / cc or less is preferred.

When the loading level of the negative electrode active material composition and the range of the electrode density are satisfied, the battery including such a negative electrode can exhibit a high cell energy density of 500 wh / L or more.

Next, a separation membrane to be inserted between the positive electrode and the negative electrode is prepared.

The separator is usable as long as it is commonly used in a lithium battery. A material having low resistance against the ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a separable membrane such as polyethylene, polypropylene or the like can be used for the lithium ion battery, and a separator membrane having excellent electrolyte impregnation ability can be used for the lithium ion polymer battery. For example, the separation membrane can be produced according to the following method.

A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separation membrane composition may be directly coated on the electrode and dried to form a separation membrane. Alternatively, after the separation membrane composition is cast and dried on a support, a separation membrane film peeled from the support may be laminated on the electrode to form a separation membrane.

The polymer resin used in the production of the separator is not particularly limited, and any material used for the binder of the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or mixtures thereof may be used.

The loading level of the negative electrode active material composition is set according to the loading level of the positive electrode active material composition. Cm ² or more, for example, 15 mg / cm ² or more, depending on the capacity per g of the negative electrode active material composition. The electrode density can be 1.5 g / cc or more, for example, 1.6 g / cc or more. As a design that places importance on energy density, the density is preferably 1.65 g / cc or more and 1.9 g / cc or less.

Next, the above-described electrolyte is prepared.

According to one embodiment, the electrolyte may include a non-aqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte in addition to the electrolyte described above.

Examples of the organic solid electrolyte include a polymer including a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, and an ionic dissociation group Can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI- such as _{LiOH, Li 3 PO 4 -Li 2} S-SiS 2 , may be used.

As shown in FIG. 1, the lithium secondary battery 1 includes an anode 3, a cathode 2, and a separator 4. The anode 3, the cathode 2 and the separator 4 are wound or folded and accommodated in the battery case 5. Then, the electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium secondary battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the lithium secondary battery may be a large-sized thin-film battery. The lithium secondary battery may be a lithium ion battery.

A separator may be disposed between the anode and the cathode to form a battery structure. The cell structure is laminated in a bi-cell structure, then impregnated with an electrolyte, and the obtained result is received in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of battery assemblies may be stacked to form a battery pack, and such battery pack may be used for all devices requiring high capacity and high output. For example, a notebook, a smart phone, an electric vehicle, and the like.

The lithium secondary battery according to an embodiment of the present invention significantly reduces the rate of DCIR increase and exhibits excellent battery characteristics as compared with a lithium secondary battery employing a general nickel-rich lithium-nickel composite oxide as a cathode active material.

The operating voltage of the lithium secondary battery to which the positive electrode, the negative electrode and the electrolyte are applied is, for example, 2.5-2.8V as a lower limit and 4.1-4.4V as an upper limit, and an energy density is 500w / L or more.

Further, the lithium secondary battery may be a power tool, for example, powered by an electric motor and moving; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (Escooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

As used herein, alkyl refers to fully saturated branched or unbranched (or straight chain or linear) hydrocarbons.

Non-limiting examples of "alkyl" include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n- pentyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl and the like.

"Alkyl" at least one hydrogen atom of an alkyl group of a halogen atom, halogen-substituted C1-C20 (for _{example: CF 3, CHF 2, CH} 2 F, CCl 3 , etc.), an alkoxy of C1-C20 alkoxy, C2-C20 of A sulfamoyl group, a sulfonic acid group or a salt thereof, a phosphoric acid or a salt thereof, a C1-C20 alkyl group, a hydroxyl group, a nitro group, a cyano group, an amino group, an amidino group, a hydrazine, a hydrazone, a carboxyl group or a salt thereof, C20 alkenyl, C2-C20 alkynyl, C1-C20 heteroalkyl, C6-C20 aryl, C6-C20 arylalkyl, C6-C20 heteroaryl, C7-C20 heteroaryl An alkyl group, a C6-C20 heteroaryloxy group, a C7-C20 heteroaryloxyalkyl group or a C7-C20 heteroarylalkyl group.

The term &quot; halogen &quot; includes fluorine, bromine, chlorine, iodine and the like.

"Alkoxy" denotes "alkyl-O- ", wherein alkyl is as described above. Examples of the alkoxy group include a methoxy group, an ethoxy group, a 2-propoxy group, a butoxy group, a t-butoxy group, a pentyloxy group and a hexyloxy group. At least one hydrogen atom of the alkoxy may be substituted with the same substituent as the alkyl group described above.

&Quot; Alkenyl &quot; refers to branched or unbranched hydrocarbons having at least one carbon-carbon double bond. Non-limiting examples of the alkenyl group include vinyl, allyl, butenyl, propenyl, isobutenyl, etc., and at least one hydrogen atom of the alkenyl may be substituted with the same substituent as the alkyl group described above.

&Quot; Alkynyl &quot; refers to branched or unbranched hydrocarbons having at least one carbon-carbon triple bond. Non-limiting examples of the "alkynyl" include ethynyl, butynyl, isobutynyl, isopropynyl, and the like.

At least one hydrogen atom of &quot; alkynyl &quot; may be substituted with the same substituent as in the alkyl group described above. &Quot; Aryl &quot; also includes groups wherein the aromatic ring is optionally fused to one or more carbon rings. Non-limiting examples of &quot; aryl &quot; include phenyl, naphthyl, tetrahydronaphthyl, and the like. Also, at least one hydrogen atom in the &quot; aryl &quot; group may be substituted with the same substituent as in the case of the above-mentioned alkyl group.

&Quot; Heteroaryl &quot; means a monocyclic or bicyclic organic group containing one or more heteroatoms selected from N, O, P, or S and the remaining ring atoms carbon. The heteroaryl group may contain, for example, from 1 to 5 hetero atoms, and may include 5-10 ring members. The S or N may be oxidized to have various oxidation states.

Examples of heteroaryl include thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, , 5-oxadiazolyl, 1,3,4-oxadiazolyl group, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, Thiadiazolyl, isothiazol-3-yl, isothiazol-4-yl, isothiazol-5-yl, oxazol- Yl, isoxazol-3-yl, 1,2,4-triazol-5-yl, Yl, pyrid-3-yl, 2-pyrazin-4-yl, 1,2,3-triazol-5-yl, tetrazolyl, 2-yl, pyrazin-4-yl, pyrazin-5-yl, 2-pyrimidin-2-yl, 4-pyrimidin-2-yl or 5-pyrimidin-2-yl.

The term &quot; heteroaryl &quot; includes those where the heteroaromatic ring is optionally fused to one or more aryl, cycloaliphatic, or heterocycle.

Will be explained in more detail through the following examples and comparative examples. However, the examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

Manufacturing example  One

A nonaqueous organic solvent obtained by mixing ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 7: 7: 46: 1 wt% of the compound was added, and 1.15 M LiPF ₆ was used as the lithium salt.

(3)

Manufacturing example  2

An electrolyte was produced in the same manner as in Production Example 1 except that the content of the compound of Formula 3 was changed to 2.9% by weight.

Manufacturing example  3

An electrolyte was prepared in the same manner as in Production Example 1, except that the compound of the formula (4) was used instead of the compound of the formula (3).

[Chemical Formula 4]

Manufacturing example  4

An electrolyte was prepared in the same manner as in Production Example 3 except that the content of the compound of Formula 4 was changed to 2.9% by weight.

Manufacturing example  5

An electrolyte was prepared in the same manner as in Preparation Example 1, except that the compound of the formula (5) was used instead of the compound of the formula (3).

 [Chemical Formula 5]

Manufacturing example  6

An electrolyte was prepared in the same manner as in Production Example 3, except that the content of the compound of Formula 4 was changed to 0.1 wt%.

Manufacturing example  7-11

Electrolytes were prepared in the same manner as in Production Example 1 except that the electrolyte compositions shown in Table 1 were changed.

Manufacturing example  12

Vinylene carbonate (VC) and sulphone (methylene methanedisulfonate) (MMDS) represented by the following general formula (15) are added in the production of electrolyte and the content of vinylene carbonate is 1 wt% based on the total weight of the electrolyte , And the content of sulphon was 0.45% by weight based on the total weight of the electrolytic solution, the same procedure as in Production Example 1 was carried out to prepare an electrolyte.

[Chemical Formula 15]

Manufacturing example  13

(EC: EMC: DMC = 20: 40: 40 by volume) in which ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate were mixed at a volume ratio of 20:40:40 as non-aqueous solvents, An electrolyte was prepared in the same manner as in Production Example 1, except that 1 wt% of VC was further added based on the weight.

Manufacturing example  14

(EC: FEC: EMC: DMC = 17: 3: 40: 1) prepared by mixing ethylene carbonate, fluoroethylene carbonate, ethylmethyl carbonate and dimethyl carbonate as nonaqueous solvents in the volume ratio of 14:46:40, : 40 volume ratio) was used, and 1% by weight of VC was further added based on the amount of the electrolyte to be added, to prepare an electrolyte.

Manufacturing example  15

(EC: FEC: EMC: DMC = 7: 7: 46) in which ethylene carbonate, fluoroethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate were mixed as non-aqueous solvents at a volume ratio of 14:46:40 : 40 volume ratio) was used, and 1% by weight of VC was further added based on the electrolyte charge amount, the same procedure as in Production Example 7 was carried out to prepare an electrolyte.

The compositions of the electrolytes prepared in Preparation Examples 1 to 14 are summarized in Table 1 below.

division Content of additive (% by weight) Solvent (vol.%) content
(weight) content
(weight%) EC FEC EMC DMC VC Sulthon Production Example 1 (3)
1 wt% 7 7 46 40 × × Production Example 2 (3)
2.9 wt% 7 7 46 40 × × Production Example 3 Formula 4
1 wt% 7 7 46 40 × × Production Example 4 Formula 4
2.9 wt% 7 7 46 40 × × Production Example 5 Formula 5
1 wt% 7 7 46 40 × × Production Example 6 Formula 4
0.1 wt% 7 7 46 40 × × Production Example 7 Formula 5
2 wt% 7 7 46 40 × × Production Example 8 Formula 5
2.9 wt% 7 7 46 40 × × Production Example 9 Formula 5
0.1 wt% 7 7 46 40 × × Production Example 10 (3)
1 wt% 7 7 46 40 One × Production Example 11 Formula 4
1 wt% 7 7 46 40 One × Production Example 12 (3)
1 wt% 7 7 46 40 One 0.45 Production Example 13 (3)
1 wt% 20 × 40 40 One  × Production Example 14 (3)
1 wt% 17 3 40 40 One  X Production Example 15 Formula 5
1 wt% 7 7 46 40 One ×

Manufacturing example  16-23

The electrolyte was prepared in the same manner as in Preparation Example 1, except that the composition of the electrolyte shown in Table 2 was changed. In Table 2 below, VC represents vinylene carbonate and Sulton represents a compound represented by the following formula (15).

 [Chemical Formula 15]

The compositions of the electrolytes prepared in Production Examples 16 to 23 are summarized in Table 2 below.

division Content of additive (% by weight) Solvent (vol.%) content
(weight%) content
(weight%) EC FEC EMC DMC VC Sulthon Production Example 16 (3)
2 wt%
2 wt% 7 7 46 40 One 0.5 Production Example 17 (3)
2.4 Weight
2.4 wt% 7 7 46 40 One 0.5 Production Example 18 (3)
1 wt%
Maleinic anhydride 1 wt%
1% by weight of lithium bis (fluorosulfonyl) imide (LiFSI) 7 7 46 40 0 0.5 Production Example 19 (3)
0.5 wt%
1 wt%
LiFSI 1 wt% 7 7 46 40 0 One Production example 20 (3)
1 wt% 7 7 46 40 0.1 0.45 Production Example 21 (3)
1 wt% 7 7 46 40 2 0.45 Production Example 22 (3)
1 wt% 20 0.5 42.5 37 One 0.45 Production Example 23 (3)
1 wt% 10 10 43 37 One 0.45

division Content of additive (% by weight) Solvent (vol.%) content
(weight%) content
(weight%) EC FEC EMC DMC Vinyl ethylene carbonate
(VEC) Sulthon Production Example 24 &Lt; tb &gt; 20 0.5 42.5 37 One 0.45

division Content of additive (% by weight) Solvent (vol.%) content
(weight%) content
(weight%) EC FEC EMC DMC Suche mountain
anhydride Sulthon Production example 25 (3)
1 wt% 20 0.5 42.5 37 One 0.45

Comparative Manufacturing Example  One

An electrolyte was prepared in the same manner as in Preparation Example 1 except that the compound of Formula 3 was not used in the production of the electrolyte.

Comparative Manufacturing Example  2

An electrolyte was prepared in the same manner as in Production Example 5 except that 3% by weight of the compound of the formula (5) was used instead of 1% by weight of the compound of the formula (5).

Comparative Manufacturing Example  3

An electrolyte was prepared in the same manner as in Comparative Preparation Example 2 except that 3% by weight of the compound of the formula (4) was used instead of 3% by weight of the compound of the formula (5).

Comparative Manufacturing Example  4

An electrolyte was prepared in the same manner as in Production Example 1 except that triflylomethanesulfonyl phosphine (aka: triflylphosphine) was used instead of the compound of the formula (3).

Comparative Manufacturing Example  5

An electrolyte was prepared in the same manner as in Comparative Preparation Example 2 except that the content of the compound of the formula (3) was changed to 3% by weight instead of the 3% by weight of the compound of the formula (5).

The compositions of the electrolytes prepared according to Comparative Production Examples 1 to 5 are summarized in Table 5 below.

division Content of additive (% by weight) Solvent (vol.%) content
(weight%) content
(weight%) EC FEC EMC DMC VC
Sulthon Comparative Preparation Example 1 x 7 7 46 40 × × Comparative Production Example 2 Formula 5
3 wt% 7 7 46 40 × × Comparative Production Example 3 Formula 4
3 wt% 7 7 46 40 × × Comparative Production Example 4 triflylphosphine
1 wt% 7 7 46 40 × × Comparative Preparation Example 5 (3)
3 wt% 7 7 46 40 × ×

Example  1: Lithium secondary battery ( Full cell )

(Preparation of positive electrode)

Cathode active material LiNi _{0 . 8} Co _{0 . 15} Al _{0 . 05} O ₂ was added with a conductive agent, DENKA BLACK, and a binder, PVDF (polyvinylidene fluoride) in a weight ratio of 97: 1.4: 1.6, and N-methylpyrrolidone (NMP) solvent was mixed so as to have a solid content of 70% .

The positive electrode active material slurry was dried on a 12 μm thick aluminum foil by a 3-roll coater, coated on both sides to a loading level of 37 mg / cm ² , dried and rolled to a density of 3.6 g / cc to prepare a positive electrode.

(Preparation of negative electrode)

Styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC) were added in a weight ratio of 97: 1.5: 1.5 to a graphite powder (purity: 99.9% up, manufactured by Mitsubishi Chemical) PD mixer (manufactured by KM Tech) to prepare a negative electrode active material slurry.

The negative electrode active material slurry was dried on a copper foil with a thickness of 10 μm by a 3-roll coater, coated on both sides to a loading level of 21.87 mg / cm ² , dried, and rolled to a density of 1.65 g / cc to prepare a negative electrode.

(Production of lithium secondary battery (full cell)

A lithium secondary battery (full cell) was produced using the anode, the cathode, the electrolyte prepared in Production Example 15, and a polyethylene separator.

Example  2

A lithium secondary battery was produced in the same manner as in Example 1, except that the electrolyte of Production Example 11 was used in place of the electrolyte of Production Example 15.

Example  3

The electrolyte of Production Example 11 was used instead of the electrolyte of Production Example 15, and the positive electrode active material LiNi _{0 .05} was used instead of the positive electrode active material LiNi _0.8 Co _0.15 Al _0.05 O _{2 . 8} Co _{0 . 15} Mn _{0 . 05} O ₂ was used in place of lithium aluminum hydride to prepare a lithium _secondary battery.

Example  4

A lithium secondary battery (full cell) was produced in the same manner as in Example 1, except that a mixture of graphite powder and SCN1 (Si particle on Graphite, manufactured by BTR Co., Ltd.) was used in producing the negative electrode. The capacity per unit weight of the cathode was about 430 mAh / g, the loading level was 18.75 mg / cm ² , and the density was 1.65 g / cc. The content of SCN1 was about 7.5 parts by weight based on 100 parts by weight of the total weight of graphite powder and SCN1.

Example  5

Cathode active material LiNi _{0 . 8} Co _{0 . 15} Al _{0 . 05} O ₂ instead of the cathode active material LiNi _{0 . 8} Co _{0 . 15} Mn _{0 . 05} O ₂ was used in place of the lithium _secondary battery of Example 4, thereby preparing a lithium _secondary battery.

Example  6

Except that a mixture of graphite powder and SCN1 (manufactured by BTR) was used instead of a mixture of graphite powder and SCN2 (manufactured by BTR), to prepare a lithium secondary battery. The capacity per unit weight of this cathode was about 430 mAh / g, the loading level was 18.75 mg / cm ² , and the density was 1.65 g / cc. The content of SCN2 was about 7.5 parts by weight based on 100 parts by weight of the total weight of graphite powder and SCN2.

Example  7

Except that the electrolyte of Production Example 14 was used in place of the electrolyte of Production Example 15, and the same negative electrode (a mixture of graphite powder and SCN1 (Si particle on Graphite, manufactured by BTR) was used as the negative electrode in Example 4) A lithium secondary battery (full cell) was produced in the same manner as in Example 1

Example  8

A lithium secondary battery (full cell) was produced in the same manner as in Example 1, except that a mixture of graphite powder and silicon oxide SiO (manufactured by Osaka Titanium Co., Ltd.) was used instead of graphite powder in producing the negative electrode. The capacity per unit weight of this cathode was about 430 mAh / g, the loading level was 18.75 mg / cm ² , and the density was 1.65 g / cc. The content of silicon oxide SiO was about 7.5 parts by weight based on 100 parts by weight of the total amount of graphite powder and silicon oxide.

Example  9

Of Preparation 15, an electrolyte and LiNi _{0. 8} Co _{0 . 15} Al _{0 . 05} O ₂ and the cathode active material LiNi _{0 . 8} Co _{0 . 15} Mn _{0 . 05} O ₂ was used in place of lithium aluminum hydride to prepare a lithium _secondary battery.

Comparative Example  One

A lithium secondary battery (full cell) was produced in the same manner as in Example 1 except that the electrolyte of Comparative Production Example 1 was used in place of the electrolyte of Production Example 15.

Comparative Example  2

A lithium secondary battery (full cell) was produced in the same manner as in Comparative Example 1, except that the negative electrode (mixture of graphite and SCN1) prepared in Example 4 was used as the negative electrode.

Comparative Example  3

A lithium secondary battery (full cell) was produced in the same manner as in Comparative Example 1, except that a negative electrode (a mixture of graphite powder and silicon oxide SiO (manufactured by Osaka Titanium Co., Ltd.) . The content of silicon oxide SiO was about 7.5 parts by weight based on 100 parts by weight of the total amount of graphite powder and silicon oxide.

Comparative Example  4

Comparative Example 1 was repeated except that the electrolyte of Comparative Production Example 4 was used in place of the electrolyte of Comparative Production Example 1 and a mixture of graphite powder and silicon oxide SiO (manufactured by Osaka Titanium Co., Ltd.) To prepare a lithium secondary battery (full cell). The content of silicon oxide SiO was about 7.5 parts by weight based on 100 parts by weight of the total amount of graphite powder and silicon oxide.

Comparative Example  5

Cathode active material LiNi _{0 . 8} Co _{0 . 15} Al _{0 . 05} O ₂ instead of the positive electrode active material _{(LiNi 0. 5 Co 0.} 2 Mn 0. 3 O 2) , and a is the same manner as in Comparative Example 1 was prepared, except for using a lithium secondary battery.

Comparative Example  6

A lithium secondary battery (full cell) was produced in the same manner as in Example 1 except that the electrolyte of Comparative Production Example 5 was used instead of the electrolyte of Production Example 1, respectively.

Example  10

The electrolyte of Preparation Example 12 was used in place of the electrolyte of Production Example 15, and a positive electrode active material LiNi _{0 .05} was used instead of the positive electrode active material LiNi _0.8 Co _0.15 Al _0.05 O _{2 . 85} Co _{0 . 10} Mn _{0 . 05} O ₂ was used in place of lithium aluminum hydride to prepare a lithium _secondary battery.

Example  11

Cathode active material LiNi _{0 . 85} Co _{0 . 10} Mn _{0 . 05} O ₂ instead of the cathode active material LiNi _{0 . 88} Co _{0 . 08} Mn _{0 . 04} O ₂ was used in place of lithium aluminum hydride to prepare a lithium _secondary battery.

Example  12

A lithium secondary battery was produced in the same manner as in Example 10 except that the electrolyte of Production Example 13 was used in place of the electrolyte of Production Example 12. [

Example  13

A lithium secondary battery was produced in the same manner as in Example 10 except that the electrolyte of Production Example 14 was used in place of the electrolyte of Production Example 12. [

Example  14

A lithium secondary battery was produced in the same manner as in Example 10 except that the electrolyte of Production Example 16 was used in place of the electrolyte of Production Example 12

Example  15

A lithium secondary battery was produced in the same manner as in Example 10 except that the electrolyte of Production Example 17 was used in place of the electrolyte of Production Example 12

Example  16

The same electrolyte as in Example 11 was used, except that the electrolyte of Production Example 18 was used in place of the electrolyte of Production Example 12, and the same negative electrode (a mixture of graphite and SCN2 (manufactured by BTR)) as in Example 6 was used. To prepare a lithium secondary battery. The content of SCN2 was about 7.5 parts by weight based on 100 parts by weight of the total weight of graphite powder and SCN2.

Example  17

The same electrolyte as in Example 11 was used, except that the electrolyte of Production Example 19 was used in place of the electrolyte of Production Example 12, and the same negative electrode (mixture of graphite and SCN2 (manufactured by BTR)) as that in Example 6 was used. To prepare a lithium secondary battery. The content of SCN2 was about 7.5 parts by weight based on 100 parts by weight of the total weight of graphite powder and SCN2.

Example  18

Cathode active material LiNi _{0 . 85} Co _{0 . 10} Mn _{0 . 05} O ₂ instead of the cathode active material LiNi _{0 . 88} Co _{0 . 8} Mn _{0 . 04} O ₂ was used and the electrolyte of Production Example 20 was used in place of the electrolyte of Production Example 12, a lithium _secondary battery was produced.

Example  19

Cathode active material LiNi _{0 . 85} Co _{0 . 10} Mn _{0 . 05} O ₂ Instead, the cathode active material LiNi _{0 . 88} Co _{0 . 8} Mn _{0 . 04} O _{2 and} that the electrolyte of Preparation Example 21 was used instead of the electrolyte of Production Example 12 was used in place of the electrolyte of Production Example 12 to prepare a lithium _secondary battery.

Example  20

The electrolyte of Production Example 22 was used in place of the electrolyte of Production Example 12 and the negative electrode was the same as that of Example 11 except that the same negative electrode (a mixture of graphite and SCN2 (manufactured by BTR)) was used. To prepare a lithium secondary battery. The content of SCN2 was about 7.5 parts by weight based on 100 parts by weight of the total weight of graphite powder and SCN2.

Example  21

A lithium secondary battery was fabricated in the same manner as in Example 11, except that the electrolyte of Production Example 23 was used in place of the electrolyte of Production Example 12, and the same negative electrode as that in Example 6 was used as the negative electrode

Evaluation example  1: High temperature Charging and discharging  Characteristics (life and DCIR )

1) Examples 1-9 and Comparative Examples 1-6

The lithium secondary batteries of Example 1-9 and Comparative Example 1-6 were charged at a constant current of 45 ° C until the voltage reached 4.30V at a current of 0.1C and then at a constant current of 0.01C Lt; RTI ID = 0.0 &gt; of &lt; / RTI &gt; Then, at the time of discharging, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 2.8 V (Mars phase, 1 ^st cycle). The charging and discharging process was performed two more times to complete the conversion process.

The lithium secondary battery having undergone the above conversion step was charged and discharged at a constant current of 1 C in a voltage range of 2.8-4.3 V at a high temperature (45 ° C). Cut off is CC-CV mode and cut-off current is 0.01C.

The above charge / discharge process was repeated 300 times.

Life characteristics and DCIR characteristics at 45 캜 of each lithium secondary battery were examined and are shown in Table 6. The lifetime of each lithium secondary battery was calculated according to the following formula 1.

[Equation 1]

Life (%) = (discharge capacity after 300 cycles / discharge capacity after one cycle) X100

The DCIR rate of rise is calculated according to Equation 2 below.

[Formula 2]

DCIR rise rate (%) = (DCIR of the cell after 300 cycles / DCIR of the cell after one cycle) X100

division life span (%) DCIR Growth Rate (%) Example 1 83 148 Example 2 84 132 Example 3 87 130 Example 4 74 158 Example 5 76 144 Example 6 78 142 Example 7 76 158 Example 8 74 156 Example 9 86 142 Comparative Example 1 73 193 Comparative Example 2 69 205 Comparative Example 3 68 190 Comparative Example 4 57 230 Comparative Example 5 72 220 Comparative Example 6 72 210

Referring to Table 6, it can be seen that the lithium secondary battery of Examples 1-9 is superior in life characteristics at 45 캜 to those of the lithium secondary batteries of Comparative Examples 1-6. It was also found that the lithium ion secondary battery of Example 1-9 had a lower DCIR increase rate at 45 ° C than the lithium secondary battery of Comparative Example 1-6.

2) Examples 10-21, 23, 24 and Comparative Example 8

The life span of the lithium secondary batteries of Examples 1-9 and Comparative Examples 1-6 and the DCIR

The lifetime and DCIR increase rate of the lithium secondary batteries of Examples 10-21, 23, 24 and Comparative Example 8 were evaluated in the same manner as in the evaluation method of the rate of rise, and are shown in Table 7 below.

division life span (%) DCIR Growth Rate (%) Example 10 87 116 Example 11 86 118 Example 12 86 147 Example 13 87 146 Example 14 86 115 Example 15 86 126 Comparative Example 8 71 158 Example 16 83 116 Example 17 83 112 Example 18 83 125 Example 19 85 122 Example 20 81 119 Example 21 83 126 Example 23 81 135 Example 24 83 138

Referring to Table 7, it can be seen that the lithium secondary battery of Examples 11-21 and 24 is improved in lifetime characteristics at 45 ° C and decreased in DCIR rising rate at 45 ° C as compared with the lithium secondary battery of Comparative Example 8 there was.

Evaluation example  2: Initial discharge capacity

The lithium secondary battery according to Example 1, Comparative Example 1 and Comparative Example 5 was charged at a constant current of 4.3 V at a rate of 0.2 C in a first cycle at room temperature (25 캜) The battery was charged at a constant voltage until it reached 0.01C, and discharged at a constant current of 2.8V at a rate of 0.2C. At this time, the initial discharge capacity of each lithium secondary battery was measured and shown in Table 8 below.

Initial capacity (mAh) Example 1 503 Comparative Example 1 498 Comparative Example 5 330

Referring to Table 8, it was found that the lithium secondary battery of Example 1 improved the initial discharge capacity as compared with the lithium secondary batteries of Comparative Examples 1 and 5.

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 exemplary embodiments or constructions. It will be apparent to those skilled in the art that various modifications and variations are possible in light of the above teachings will be. Accordingly, the scope of protection of the present invention should be determined by the appended claims.

1: lithium secondary battery 2: negative electrode
3: anode 4: membrane
5: Battery case 6: Cap assembly

Claims (22)

A compound represented by Formula 1 below; Lithium salts; And an organic solvent,
Wherein the content of the compound represented by the formula (1) is less than 3% by weight based on the total weight of the electrolyte:
[Chemical Formula 1]

In the formula (1), R ₁ to R ₁₅ independently represent hydrogen, fluorine, a substituted or unsubstituted C1-C10 alkyl group, or a substituted or unsubstituted C6-C10 aryl group. The method according to claim 1,
Wherein the content of the compound represented by Formula 1 is 0.1 to 2.9 wt%. The method according to claim 1 ,
The compound represented by the formula (1) is a compound represented by the following formula (2): &lt; EMI ID =
(2)

In the formula (2), R ₃ , R ₈ and R ₁₃ are each independently hydrogen, fluorine or a methyl group. The method according to claim 1,
Wherein the compound represented by Formula 1 is at least one selected from the compounds represented by Chemical Formulas 3 to 6, 6a and 6b:
(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

[Chemical Formula 6a]

[Formula 6b]

The method according to claim 1,
Wherein the compound represented by Formula 1 is at least one selected from a compound represented by Formula 3 or a compound represented by Formula 6b:
(3)

[Formula 6b]

The method according to claim 1,
Wherein the electrolyte further comprises at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate (VEC), maleic anhydride and succinic anhydride. The method according to claim 6,
Wherein the content of at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate (VEC), maleic anhydride and succinic anhydride is 0.1 to 2% by weight based on the total weight of the electrolyte. The method according to claim 6,
Wherein the electrolyte further comprises fluoroethylene carbonate, and the content of fluoroethylene carbonate is 0.5 to 10% by volume based on the total volume of the organic solvent. The method according to claim 1,
Wherein the electrolyte comprises 0.1 to 2% by weight of maleic anhydride based on the total weight of the electrolyte. The method according to claim 1,
Wherein the electrolyte further comprises a disulfide-based compound represented by the following general formula (7): &lt; EMI ID =
(7)

In Formula (7), R ₁ and R ₂ are independently a substituted or unsubstituted C ₁ -C ₃₀ alkylene group,
The substituent of the substituted C ₁ -C ₃₀ alkylene group may be substituted with at least one substituent selected from the group consisting of halogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, Butynyl, propenyl, or butenyl group. The term &quot; alkenyl &quot; 11. The method of claim 10,
Wherein the disulfide compound is at least one selected from compounds represented by the following formula (7a) and the content of the disulfide compound is 0.5 to 2% by weight based on the total weight of the electrolyte:
[Formula 7a]

The electrolyte for a lithium secondary battery according to claim 1, wherein the concentration of the lithium salt is 0.1 to 5.0 M. The method according to claim 1,
Wherein the lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₂ F ₅ SO ₃ , Li (FSO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , ₂ CF ₂ CF ₃ ) ₂ , and a compound represented by any of formulas (8) to (11):
[Chemical Formula 8]

[Chemical Formula 10]

The method according to claim 1,
Wherein the lithium salt is composed of LiPF ₆ , Li (FSO ₂ ) ₂ N and / or a compound represented by the formula (11) (LiDFOB), and the content of the lithium salt is 0.8 M to 2 M The method according to claim 1,
Wherein the electrolyte comprises i) from 0.2 to 2.4% by weight, based on the total weight of the electrolyte, of tri (4-fluorophenyl) phosphine, triphenylphosphine, tri (4-methylphenyl) phosphine, tris (Phenyl) phosphine and tris (pentafluorophenyl) phosphine, and at least one selected from the group consisting of ethylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and vinylene carbonate,
ii) from 0.2 to 2.% by weight, based on the total weight of the electrolyte, of tri (4-fluorophenyl) phosphine, triphenylphosphine, tri (4-methylphenyl) phosphine, tris (2,4- ) An electrolyte for a lithium secondary battery comprising at least one selected from phosphine and tris (pentafluorophenyl) phosphine, and ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and vinylene carbonate. anode;
cathode; And
And at least one selected from reaction products of an electrolyte and an electrolyte according to any one of claims 1 to 15. A lithium secondary battery comprising: 17. The method of claim 16,
Wherein the positive electrode comprises a nickel-rich lithium-nickel composite oxide having a nickel content of 70 to 95 mol% based on a total molar amount of the transition metal. 18. The method of claim 17,
Wherein the nickel-rich lithium-nickel composite oxide is a compound represented by the following formula (14):
[Chemical Formula 14]
_{Li a Ni x Co y Mn z} M c O 2 - b A b
1, 0? Z? 1, 0? C <1, x + y + z + c = 1, 0? B? 0.2 , M is at least one element selected from the group consisting of vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr) Zn), titanium (Ti), aluminum (Al) and boron (B)
A is F, S, Cl, Br or a combination thereof. 18. The method of claim 17,
Wherein the nickel-rich lithium-nickel composite oxide is a compound represented by the following general formula (14a) or (14b):
[Chemical Formula 14a]
LiNi _x Co _y Mn _z O ₂
[Chemical Formula 14b]
LiNi _x Co _y Al _z O ₂
In the above formulas (14a) and (14b), 0.8? X? 0.95, 0 <y? 0.2, 0 <z? 0.1. 17. The method of claim 16,
Wherein the negative electrode comprises at least one selected from the group consisting of a silicon compound, a carbonaceous material, a composite of a silicon compound and a carbonaceous material, and a silicon oxide (SiO _x (0 <x <2)). 17. The method of claim 16,
Wherein the lithium secondary battery has a direct current internal resistance (DCIR) increase rate of 165% or less after 300 cycles of charging and discharging at 45 캜. 17. The lithium secondary battery of claim 16, wherein the lithium secondary battery has a cell energy density of 500 Wh / L or more.

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