KR20150014074A - Electrolyte for high voltage lithium secondary battery and high voltage lithium secondary battery using the electrolyte - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery comprising an electrolyte additive containing a nonaqueous organic solvent, lithium salt, and fluorine, in which 0.01-3 w% of the electrolyte additive and 0.1-3 M of the lithium salt are contained, the lithium secondary battery using the electrolyte. According to the lithium secondary battery of present invention, thermal stability is excellent, and discharge characteristics are excellent at high temperatures.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte for a high-voltage lithium secondary battery and a high-voltage lithium secondary battery using the same,

The present invention relates to an electrolyte of a lithium secondary battery and a lithium secondary battery using the electrolyte. More particularly, the present invention relates to an electrolyte for a high-voltage lithium secondary battery which is excellent in high temperature stability and exhibits high discharge capacity characteristics even at a high temperature, The present invention relates to a secondary battery.

2. Description of the Related Art In recent years, there has been a rapid increase in demand for rechargeable batteries that are used repeatedly by charging and discharging power from portable electronic devices such as mobile phones, laptop computers, and digital cameras, electric vehicles, and electric bicycles.

Particularly, since the product performance of an electric vehicle depends on a secondary battery, which is a core component, development of a high performance secondary battery is required. The characteristics required for such a secondary battery include various aspects such as charge / discharge characteristics, life characteristics, high rate characteristics, and stability at high temperatures.

Among secondary batteries, lithium secondary batteries are the most popular because they have high voltage and high energy density. In particular, a lithium secondary battery using a complex oxide of a spinel structure as a cathode active material has a high energy density due to a high voltage, and thus is a battery of the most attention.

Conventional lithium _secondary batteries use LiCoO ₂ as a positive electrode and carbon as a negative electrode. However, the use of cobalt (Co) used as a cathode active material is required to develop a new replaceable cathode active material because it has a low storage capacity, high cost, toxicity to human body and environmental pollution problem.

Although the positive electrode active material LiNiO ₂ have been studied as a lithium secondary battery, LiNiO _2, which forms a layer structure has a problem in thermal stability as well as difficulty in material synthesis of the stoichiometric amount.

In recent years, a lithium-transition metal-manganese oxide system (for example, LiNi _x Mn _{2 -x} O ₄ (0 <x <1)) having a spinel structure has been proposed as a material capable of providing a high- ) Cathode active materials have been actively studied. However, the lithium-transition metal-manganese oxide-based cathode active material has eluted manganese at a high temperature (for example, 50 to 70 ° C), resulting in deterioration of the life characteristics of the lithium secondary battery. Therefore, it is possible to suppress the elution of manganese at a high temperature, A plan is needed to improve the lifetime characteristics.

An object of the present invention is to provide an electrolyte for a high-voltage lithium secondary battery which is excellent in high-temperature stability and can exhibit high discharge capacity characteristics even at a high temperature, and a high-voltage lithium secondary battery using the same.

The _{invention, LiM x Mn 2 -x O 4} (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, Cu 1 or more kinds of transition metals selected from a), LiNi _x M _y Mn _{2 -xy} O ₄ (at least one transition metal selected from the group consisting of Fe, Cr, Co, Zr, Zn, V and Cu), 0 <x <1, 0 <y < _{LiM x Mn 1 -x PO 4 (} 0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, at least one selected from the group consisting of Cu-transition metal), and LiM _x Co _{1 -x} PO ₄ ( A negative electrode, a separator, and an electrolyte solution containing at least one positive electrode active material selected from the group consisting of 0 <x <1 and M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, Wherein the electrolyte additive is contained in an amount of 0.01 to 3% by weight based on the electrolyte, and the lithium salt is added to the electrolyte solution, wherein the electrolyte solution contains the non-aqueous organic solvent, the lithium salt, and the fluorine- And the electrolyte solution is contained in the electrolyte solution at a concentration of 0.1 to 3 M.

The electrolyte additive may include LiF.

The electrolyte additive may further comprise 3,5-bis (trifluoromethyl) -pyrazole, wherein the electrolyte additive is selected from the group consisting of LiF and the 3,5-bis (trifluoromethyl) To 10 wt%.

The lithium salt may be composed of at least one material selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ .

The non-aqueous organic solvent may be a solvent in which ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 0.1-10.

The electrolytic solution may further comprise an ionic liquid, wherein the ionic liquid is contained in the electrolytic solution in an amount of 0.01 to 60% by weight, the ionic liquid is a substance in which a cation and an ion are paired and is liquid at room temperature, Wherein the anion comprises at least one material selected from the group consisting of piperidinium, pyrolidinium and imidazolium, the anion being bis (trifluoromethylsulfonyl) imide, imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), and bis (fluorosulfonyl) imide. .

The electrolytic solution may be selected from the group consisting of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-propyl-piperidinium bis (trifluoromethylsulfonyl) Methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, Pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium bis (fluorosulfonyl) imide (methyl-ethyl-piperidinium bis (fluorosulfonyl) imide, methyl-propyl-piperidinium bis (fluorosulfonyl) imide, methyl-ethyl-pyrrolidinium bis (fluorosulfonyl) imide, Methyl-ethyl-pyrolidinium bis (fluorosulfonyl) imide) and methyl-propyl-pyrrolidone Pyrolidinium bis (fluorosulfonyl) imide. The ionic liquid may be added to the electrolytic solution in an amount of 0.01 to 60 wt.%, .

In addition, the present _{invention, LiM x Mn 2 -x O 4} (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, 1 or more kinds of transition metals selected from Cu), LiNi _x M _{y Mn 2 -xy O 4 (0} <x <1, 0 <y <1, 0 <x + y <1, M is Fe, Cr, Co, Zr, Zn, V, a transition metal at least one selected from Cu _{), LiM x Mn 1 -x PO} 4 (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, at least one selected from the group consisting of Cu-transition metal), and LiM _x Co _{1 -x} PO ₄ inserted into the positive electrode, the lithium ion comprising one positive electrode of two or more active materials selected from the group consisting of (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, one or more kinds of transition metals selected from Cu) A separator for preventing a short circuit between the positive electrode and the negative electrode, and an electrolyte solution in which a lithium salt is dissolved between the positive electrode and the negative electrode, wherein the electrolyte contains a non-aqueous organic A solvent, a lithium salt, and an electrolyte additive including fluorine, Wherein the lithium salt is contained in an amount of 0.01 to 3 wt% based on the electrolyte, and the lithium salt is contained in the electrolyte at a concentration of 0.1 to 3 M.

The electrolyte additive may include LiF.

The electrolyte additive may further comprise 3,5-bis (trifluoromethyl) -pyrazole, wherein the electrolyte additive is selected from the group consisting of LiF and the 3,5-bis (trifluoromethyl) To 10 wt%.

The lithium salt may be composed of at least one material selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ .

The non-aqueous organic solvent may be a solvent in which ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 0.1-10.

The electrolytic solution may further comprise an ionic liquid, wherein the ionic liquid is contained in the electrolytic solution in an amount of 0.01 to 60% by weight, the ionic liquid is a substance in which a cation and an ion are paired and is liquid at room temperature, Wherein the anion comprises at least one material selected from the group consisting of piperidinium, pyrolidinium and imidazolium, the anion being bis (trifluoromethylsulfonyl) imide, imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), and bis (fluorosulfonyl) imide. .

The electrolytic solution may be selected from the group consisting of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-propyl-piperidinium bis (trifluoromethylsulfonyl) Methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, Pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium bis (fluorosulfonyl) imide (methyl-ethyl-piperidinium bis (fluorosulfonyl) imide, methyl-propyl-piperidinium bis (fluorosulfonyl) imide, methyl-ethyl-pyrrolidinium bis (fluorosulfonyl) imide, Methyl-ethyl-pyrolidinium bis (fluorosulfonyl) imide) and methyl-propyl-pyrrolidone Pyrolidinium bis (fluorosulfonyl) imide. The ionic liquid may be added to the electrolytic solution in an amount of 0.01 to 60 wt.%, .

According to the present invention, it is possible to improve the stability of a high-voltage lithium secondary battery at a high temperature (for example, 50 ° C or higher) by using a small amount of an electrolyte additive containing fluorine, Voltage lithium-ion secondary battery.

The high-temperature stability of the high-voltage lithium secondary battery can be improved, so that the reliability of the lithium secondary battery can be improved.

The electrolyte solution of the lithium secondary battery according to the present invention can be stable even at a high temperature, thus greatly alleviating the question of the stability of the high-voltage high-output lithium secondary battery and providing a basis for promoting the commercialization of the electric vehicle battery.

FIG. 1 is a graph showing a discharge capacity of a lithium secondary battery manufactured using a 5V-level cathode active material LiNi _{0 .5} Mn _{1 .5} O ₄ according to Experimental Example 1 by temperature.
FIG. 2 is a graph showing a discharge capacity of a lithium secondary battery manufactured using a cathode active material LiNi _{0 .5} Mn _{1 .5} O ₄ of ₅ V according to Experimental Example 2 and using BTFMP as an electrolyte additive.
FIG. 3 is a graph showing a discharge capacity of a lithium secondary battery manufactured using LiF as a cathode active material LiNi _{0 .5} Mn _{1 .5} O ₄ according to Experimental Example 3 and a 5 V-type cathode active material LiNi _0.5 Mn _{1 .5} O ₄ .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

It is necessary to improve the energy density of the lithium secondary battery as a necessary condition for the application of the lithium secondary battery to the electric vehicle. As a method for improving the energy density of the lithium secondary battery, there is a method of increasing the output voltage of the energy storage material or increasing the storage capacity.

Since an electric vehicle is a high output device using a high current, the operating temperature of the lithium secondary battery is high due to high output. Maintaining reliability in the operation of lithium secondary batteries at high temperatures is just as important as developing new materials. The transition metal-higher operating temperatures (e.g., above 50 ℃) lithium manganese oxide-based (for _{example, LiM x Mn 2 -x O 4} (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn , V, 1 or more kinds of transition metals selected from _{Cu), LiNi x M y Mn} 2-xy O 4 (0 <x <1, 0 <y <1, 0 <x + y <1, M is Fe, Cr, Co, Zr, Zn, V, Cu 1 or more kinds of transition metals) selected _{from, LiM x Mn 1 -x PO 4} (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, Cu The positive electrode active material has a problem that manganese is eluted or decomposed and energy storage characteristics to be provided by the electrode due to elution or decomposition are often extinguished.

The present invention relates to a lithium secondary battery comprising LiM _x Mn _{2 -x} O ₄ (0 <x <1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, V and Cu) _x M _y Mn _{2 -xy} O ₄ (0 <x <1, 0 <y <1, 0 <x + y <1, M is at least one selected from Fe, Cr, Co, Zr, Zn, transition _{metal), LiM x Mn 1-x} PO 4 (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, at least one selected from the group consisting of Cu-transition metal), and LiM _x Co _{1 - wherein at} least one of the positive electrode active material selected from the group consisting of Li 2 PO ₄ (0 <x <1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, An electrolyte solution of a lithium secondary battery is proposed to improve characteristics. In the present invention, it has been confirmed through experiments that the use of an additive for an electrolyte containing fluorine and an additive for an electrolyte containing fluorine can prevent the discharge capacity of the lithium secondary battery from being lowered in order to prevent a drastic decrease in discharge capacity.

The electrolyte of the lithium secondary battery according to the preferred embodiment of the present invention is made of LiM _x Mn _{2 -x} O ₄ (0 <x <1, M is one selected from Ni, Fe, Cr, Co, Zr, at least one transition _{metal), LiNi x M y Mn 2} -xy O 4 (0 <x <1, 0 <y <1, 0 <x + y <1, M is Fe, Cr, Co, Zr, Zn, V , at least one transition metal) selected from the group consisting of _{Cu, LiM x Mn 1 -x PO} 4 (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, a transition metal at least one selected from Cu ) And at least one positive electrode active material selected from LiM _x Co _{1 -x} PO ₄ (0 <x <1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, An electrolyte, and a lithium secondary battery including an anode, a cathode, a separator, and an electrolyte solution, wherein the electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an electrolyte additive including fluorine. The electrolyte additive is contained in the electrolyte in an amount of 0.01 to 3 wt%, and the lithium salt may be contained in the electrolyte in a concentration of 0.1 to 3 M.

The electrolyte additive may include LiF.

The electrolyte additive may further comprise 3,5-bis (trifluoromethyl) pyrazole, and the electrolyte additive may include the LiF and the 3,5-bis (trifluoromethyl) (Trifluoromethyl) -pyrazole may be mixed in a weight ratio of 1: 0.1 to 10.

The lithium salt may be composed of at least one material selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ .

The non-aqueous organic solvent may be a solvent in which ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 0.1-10.

The electrolytic solution may further comprise an ionic liquid, wherein the ionic liquid is contained in the electrolytic solution in an amount of 0.01 to 60% by weight, the ionic liquid is a substance in which a cation and an ion are paired and is liquid at room temperature, Wherein the anion comprises at least one material selected from the group consisting of piperidinium, pyrolidinium and imidazolium, the anion being bis (trifluoromethylsulfonyl) imide, imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), and bis (fluorosulfonyl) imide. .

The electrolytic solution may be selected from the group consisting of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-propyl-piperidinium bis (trifluoromethylsulfonyl) Methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, Pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium bis (fluorosulfonyl) imide (methyl-ethyl-piperidinium bis (fluorosulfonyl) imide, methyl-propyl-piperidinium bis (fluorosulfonyl) imide, methyl-ethyl-pyrrolidinium bis (fluorosulfonyl) imide, Methyl-ethyl-pyrolidinium bis (fluorosulfonyl) imide) and methyl-propyl-pyrrolidone Pyrolidinium bis (fluorosulfonyl) imide. The ionic liquid may be added to the electrolytic solution in an amount of 0.01 to 60 wt.%, .

The lithium _secondary battery according to a preferred embodiment of the present invention is a lithium _secondary battery in which LiM _x Mn _{2 -x} O ₄ (0 <x <1, M is at least one selected from Ni, Fe, Cr, Co, Zr, Zn, transition _{metal), LiNi x M y Mn 2} -xy O 4 (0 <x <1, 0 <y <1, 0 <x + y <1, M is Fe, Cr, Co, Zr, Zn, V, Cu at least one transition metal) selected _{from, LiM x Mn 1 -x PO 4} (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, 1 or more kinds of transition metals selected from Cu) and At least one positive electrode active material selected from LiM _x Co _{1 -x} PO ₄ (0 <x <1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, A lithium secondary battery comprising: an anode; a cathode including a negative active material capable of inserting or removing lithium ions; a separator for preventing short circuit between the positive electrode and the negative electrode; and an electrolyte solution in which a lithium salt is dissolved between the positive electrode and the negative electrode , The electrolytic solution contains a non-aqueous organic solvent, a lithium salt, and an electrolyte additive including fluorine The. The electrolyte additive is contained in the electrolyte in an amount of 0.01 to 3 wt%, and the lithium salt may be contained in the electrolyte in a concentration of 0.1 to 3 M.

The electrolyte additive may include LiF.

The electrolyte additive may further comprise 3,5-bis (trifluoromethyl) -pyrazole, wherein the electrolyte additive is selected from the group consisting of LiF and the 3,5-bis (trifluoromethyl) To 10 wt%.

The lithium salt may be composed of at least one material selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ .

The non-aqueous organic solvent may be a solvent in which ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 0.1-10.

The electrolytic solution may further comprise an ionic liquid, wherein the ionic liquid is contained in the electrolytic solution in an amount of 0.01 to 60% by weight, the ionic liquid is a substance in which a cation and an ion are paired and is liquid at room temperature, Wherein the anion comprises at least one material selected from the group consisting of piperidinium, pyrolidinium and imidazolium, the anion being bis (trifluoromethylsulfonyl) imide, imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), and bis (fluorosulfonyl) imide. .

The electrolytic solution may be selected from the group consisting of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-propyl-piperidinium bis (trifluoromethylsulfonyl) Methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, Pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium bis (fluorosulfonyl) imide (methyl-ethyl-piperidinium bis (fluorosulfonyl) imide, methyl-propyl-piperidinium bis (fluorosulfonyl) imide, methyl-ethyl-pyrrolidinium bis (fluorosulfonyl) imide, Methyl-ethyl-pyrolidinium bis (fluorosulfonyl) imide) and methyl-propyl-pyrrolidone Pyrolidinium bis (fluorosulfonyl) imide. The ionic liquid may be added to the electrolytic solution in an amount of 0.01 to 60 wt.%, .

Hereinafter, an electrolytic solution of a lithium secondary battery using an electrolyte containing fluorine, a lithium secondary battery using the electrolytic solution and a cathode active material, and a manufacturing method thereof will be described.

A positive electrode active material, a conductive material, a binder and a solvent are mixed to prepare a composition for a positive electrode for a lithium secondary battery.

The composition for a lithium secondary battery positive electrode comprises a positive electrode active material, 2 to 25 parts by weight of a conductive material per 100 parts by weight of the positive electrode active material, 2 to 25 parts by weight of a binder with respect to 100 parts by weight of the positive electrode active material, And 100 to 500 parts by weight of a solvent. When the mixture is stirred for a predetermined time (for example, 10 minutes to 12 hours) using a mixer such as a conditioning mixer for uniform mixing, a composition for a lithium secondary battery anode in a slurry state suitable for electrode production Can be obtained. A mixer, such as a conditioning mixer, enables the preparation of a uniformly mixed composition for a lithium secondary battery anode.

The cathode active material is a material capable of providing a high voltage of 5V class, and LiM _x Mn _{2 -x} O ₄ (0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V , Cu), LiNi _x M _y Mn _{2 -xy} O ₄ (0 <x <1, 0 <y <1, 0 <x + y <1, M is at least one element selected from the group consisting of Fe, Zr, Zn, V, 1 or more kinds of transition metals selected from _{Cu), LiM x Mn 1 -x} PO 4 (0 <x <1, M is Ni, Fe, Cr, selected from the group consisting of Co, Zr, Zn, V, Cu One or more transition metals selected from LiM _x Co _{1 -x} PO ₄ (0 <x <1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, More than one kind of cathode active material is used.

The conductive material is not particularly limited as long as it is an electron conductive material that does not cause chemical changes. Examples of the conductive material include natural graphite, artificial graphite, carbon black (Super-P black), acetylene black, , Metal powders such as nickel, aluminum, and silver, metal fibers, and mixtures thereof.

The binder may be selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVDF), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyvinyl butyral vinyl butyral (PVB), poly-N-vinylpyrrolidone (PVP), styrene butadiene rubber (SBR), polyamide-imide, polyimide or the like And the like can be used.

The solvent may be an organic solvent such as ethanol (EtOH), acetone, isopropyl alcohol, N-methyl pyrrolidone (NMP), propylene glycol (PG) or water.

A composition for a positive electrode of a lithium secondary battery in which a positive electrode active material, a binder, a conductive material and a solvent are mixed is cast on a metal (alloy) current collector such as an aluminum current collector by a doctor blade method, (roll press machine) or the like to form an electrode, thereby forming a positive electrode of the lithium secondary battery.

The lithium secondary battery anode manufactured as described above may be usefully applied to a lithium secondary battery of a desired type such as a coin cell.

As described above _{LiM x Mn 2 -x O 4 (} 0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, Cu 1 or more kinds of transition metals selected from a), LiNi _x M _y Mn _{2 -xy} O ₄ (at least one transition metal selected from the group consisting of Fe, Cr, Co, Zr, Zn, V and Cu), 0 <x <1, 0 <y < _{LiM x Mn 1 -x PO 4 (} 0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, at least one selected from the group consisting of Cu-transition metal), and LiM _x Co _{1 -x} PO ₄ ( At least one transition metal selected from the group consisting of Ni, Fe, Cr, Co, Zr, Zn, V and Cu) A separator for preventing the short circuit between the positive electrode and the negative electrode is disposed between the positive electrode and the negative electrode, and a lithium salt is dissolved between the positive electrode and the negative electrode A lithium secondary battery can be manufactured by injecting an electrolytic solution.

The negative electrode may include at least one negative electrode active material selected from lithium metal, lithium alloy, crystalline carbon, amorphous carbon, carbon composite, and carbon fiber. The negative electrode may also be produced by the same or similar method as the method for producing the positive electrode.

The separator may be used in a battery field such as a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyester nonwoven fabric, a polyacrylonitrile porous separator, a poly (vinylidene fluoride) hexafluoropropane copolymer porous separator, a cellulose porous separator, a kraft paper or a rayon fiber And is not particularly limited as long as it is a commonly used separation membrane.

The electrolytic solution includes a non-aqueous organic solvent, a lithium salt, and an electrolyte additive including fluorine.

The electrolyte of the electrolyte to be filled in the lithium secondary battery of the present invention is one in which a lithium salt is dissolved. The lithium salt is not particularly limited and may be, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ , LiAsF _6, a mixture thereof, and the like. It is preferable that the lithium salt is contained in the electrolytic solution at a concentration of 0.1 to 3M.

The solvent constituting the electrolytic solution is not particularly limited as long as it is a non-aqueous organic solvent, and examples thereof include a cyclic carbonate solvent, a chain carbonate solvent, an ester solvent, an ether solvent, a nitrile solvent, Etc. may be used. Examples of the cyclic carbonate solvent include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. As the chain carbonate solvent, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like can be used. Examples of the ester solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and? -Butyrolactone. The ether solvents include 1,2-dimethoxyethane, Ethoxyethane, tetrahydrofuran, 1,2-dioxane, 2-methyltetrahydrofuran and the like can be used. As the nitrile solvent, acetonitrile and the like can be used. As the amide solvent, dimethylformamide Can be used.

The electrolyte additive may include LiF. The electrolyte additive may further comprise 3,5-bis (trifluoromethyl) pyrazole in addition to LiF, wherein the electrolyte additive is selected from the group consisting of LiF and the 3,5-bis (trifluoromethyl) Pyrazole is preferably mixed in a weight ratio of 1: 0.1 to 10. The electrolyte additive is preferably contained in an amount of 0.01 to 3 wt% in the electrolyte solution in terms of high-temperature stability of the lithium secondary battery and high-temperature holding of the discharge capacity. When 0.01% by weight of the electrolyte additive is added, 99.99% by weight of the remaining components (lithium salt and solvent) constituting the electrolytic solution are contained. When 3% by weight of the electrolyte additive is added, Solvent) is 97 wt%. Experiments have confirmed that the use of a fluorine-containing electrolyte additive is used to prevent a drastic decrease in the discharge capacity of the lithium secondary battery and that the discharge capacity of the lithium secondary battery can be prevented from decreasing by using an additive containing an electrolyte containing fluorine.

The electrolytic solution may further contain an ionic liquid. The ionic liquid is preferably contained in the electrolytic solution in an amount of 0.01 to 60 wt% from the viewpoints of high-temperature stability of the lithium secondary battery and high-temperature discharge of the discharge capacity. When 0.01% by weight of the ionic liquid is added, 99.99% by weight of the remaining components (lithium salt, solvent and electrolyte additive) constituting the electrolytic solution are contained. When 60% by weight of the ionic liquid is added, The components (lithium salt, solvent and electrolyte additive) are contained in an amount of 40% by weight. The ionic liquid is a material in which a cation and an ion are paired and an ion pair is a liquid at room temperature or a material which melts at a temperature slightly higher than room temperature. The ionic liquid can be used as a solvent for an electrolyte because it is a liquid at about room temperature. The ionic liquid is not a flammable solvent and has a characteristic of being highly flame retardant or nonflammable, and thus has an attractive characteristic in a battery in which a fire can occur. These cations are cyclic, such as piperidinium, pyrolidinium, and imidazolium, which give the most stable appearance in the cell. The ring structure can be modified into many similar structures by replacing a plurality of alkyl groups. The non-cyclic ones are quaternary ammoniums, and four different or identical alkyl groups form ammonium cations, so that a myriad of cations can be made. The anion may be bis (trifluoromethylsulfonyl) imide (hereinafter referred to as TFSI), tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), tetrafluoroborate Bis (fluorosulfonyl) imide (hereinafter referred to as 'FSI'), and the like. Among the ionic liquids, mention may be made especially of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium TFSI, methyl-propyl-piperidinium bis (trifluoromethylsulfonyl) methyl-ethyl-pyrolidinium TFSI, methyl-ethyl-pyrrolidinium TFSI, methyl-propyl-pyrrolidinium bis (trifluoromethylsulfate) Methyl-ethyl-piperidinium FSI, methyl-ethyl-piperidinium FSI, methyl-ethyl-piperidinium FSI, Methyl-ethyl-pyrolidinium FSI, methyl-ethyl-pyrrolidinium FSI, methyl-propyl-pyrrolidinium bis (fluorosulfonyl) imide (Methyl-proply-pyrolidinium FSI), or a mixture thereof, is highly applicable to lithium secondary batteries. It gives over.

Hereinafter, experimental examples according to the present invention will be specifically shown, and the present invention is not limited by the following experimental examples.

In the experimental examples of the present invention, the use of 3,5-bis (trifluoromethyl) pyrazole (hereinafter referred to as "BTFMP") as a molecule containing a large amount of fluorine In addition, LiF was used as an electrolyte additive and the electrode was protected at high temperature by fluorine ions contained in LiF.

<Experimental Example 1>

A positive electrode active material, a conductive material, a binder and a solvent were mixed to form a composition for a positive electrode for a lithium secondary battery. As the cathode active material using LiNi _{0 .5} Mn _{1 .5} O ₄ was used, as the conductive material was used as the carbon black (Super-P Black), as the binder is polyvinylidene fluoride (PVDF) Respectively. Specifically, N-methylpyrrolidone (NMP) as a solvent and polyvinylidene fluoride (PVDF) as a binder were stirred in a conditioning mixer for 10 minutes, here in the positive active material LiNi _{0 .5} Mn _{1 .5} O ₄ with a re-mixing the conductive carbon black (Super-P black), and then, after a given viscosity according to a little more added to N- methylpyrrolidone (NMP) , And further stirred for 30 minutes. The positive electrode active material, the conductive material and the binder were added in a weight ratio of 90: 5: 5. The solvent was added in an amount of 200 parts by weight based on 100 parts by weight of the cathode active material.

An aluminum current collector was laid on a glass plate, and a composition for a lithium secondary battery anode in a slurry state was cast on an aluminum current collector by a doctor blade method, followed by drying at 100 ° C for 24 hours.

The dried product was compressed at a compression ratio of 20 to 25% using a roll press machine at 120 ° C to complete the electrode (anode) of the lithium secondary battery.

A coin cell was fabricated to evaluate the characteristics of the electrode. The coin cell used was the 2016 standard and the fabricated electrode was used as the anode and lithium metal was used as the cathode. The electrolyte was composed of ethylene carbonate (EC) and diethyl carbonate ; DEC) is 1: 1.0M LiPF ₆ is used that is soluble in the electrolyte): 1 solvent (1 EC / DEC (1) mixed at a weight ratio of.

FIG. 1 is a graph showing a discharge capacity of a lithium secondary battery manufactured using a 5V-level cathode active material LiNi _{0 .5} Mn _{1 .5} O ₄ according to Experimental Example 1 by temperature. 1 (a) shows the discharge capacity at 25 ° C, and (b) shows the discharge capacity at 55 ° C.

Referring to FIG. 1, although the discharge capacity retention characteristic is excellent at a room temperature of 25 ° C, the discharge capacity rapidly decreases at a high temperature of 55 ° C, and the discharge capacity disappears within 40 cycles. The reason why the discharge capacity is extinguished is that the first reason is due to the elution phenomenon in which the electrode (anode) melts and flows down at a high temperature, and the second reason is that the decomposition products of the ions and the electrolytic solution, .

<Experimental Example 2>

The same positive electrode active material as in Experimental Example 1 LiNi _{0 .5} using Mn _{1 .5} O _4, thereby completing the electrode (anode) for lithium secondary battery.

A coin cell was fabricated to evaluate the characteristics of the electrode. The coin cell used was the 2016 standard and the fabricated electrode was used as the anode and lithium metal was used as the cathode. The electrolyte was composed of ethylene carbonate (EC) and diethyl carbonate (EC / DEC (1: 1)) mixed in a volume ratio of 1: 1 was used as the electrolytic solution additive, and 1.0 M LiPF ₆ was dissolved in the electrolyte and BTFMP was dissolved in the electrolyte additive. The BTFMP contained 1 wt% in the electrolytic solution.

FIG. 2 is a graph showing a discharge capacity of a lithium secondary battery manufactured using a cathode active material LiNi _{0 .5} Mn _{1 .5} O ₄ of ₅ V according to Experimental Example 2 and using BTFMP as an electrolyte additive. 2 shows the discharge capacity at 55 캜.

Referring to FIG. 2, the discharge capacity characteristics at 55 ° C. were superior to those in FIG. 1. BTFMP, which is an electrolyte additive containing a large amount of fluorine, is used, which is advantageous for maintaining the discharge capacity at high temperatures.

<Experimental Example 3>

The same positive electrode active material as in Experimental Example 1 LiNi _{0 .5} using Mn _{1 .5} O _4, thereby completing the electrode (anode) for lithium secondary battery.

A coin cell was fabricated to evaluate the characteristics of the electrode. The coin cell used was the 2016 standard and the fabricated electrode was used as the anode and lithium metal was used as the cathode. The electrolyte was composed of ethylene carbonate (EC) and diethyl carbonate (EC / DEC (1: 1)) mixed in a volume ratio of 1: 1 was used as the electrolytic solution additive, and 1.0 M LiPF ₆ was dissolved in the electrolyte and LiF was dissolved in the electrolyte additive. The LiF was contained in the electrolytic solution in an amount of 0.2 wt% and 0.4 wt%.

FIG. 3 is a graph showing a discharge capacity of a lithium secondary battery manufactured using LiF as a cathode active material LiNi _{0 .5} Mn _{1 .5} O ₄ according to Experimental Example 3 and a 5 V-type cathode active material LiNi _0.5 Mn _{1 .5} O ₄ . 3 shows the discharge capacity at 55 캜. Fig. 3 (a) shows a case where LiF is contained in an electrolyte solution in an amount of 0.2 wt%, and Fig. 3 (b) shows a case where LiF is contained in an electrolyte solution in an amount of 0.4 wt%.

Referring to FIG. 3, the discharge capacity characteristics at 55 ° C. are superior to those in FIG. 1. The use of LiF, an electrolyte additive containing fluorine, has shown favorable properties for maintaining discharge capacity at high temperatures. It was confirmed that the discharge capacity retention characteristic can be improved by the fluorine ion by LiF.

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, This is possible.

Claims (14)

_{LiM x Mn 2 -x O 4 (} 0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, Cu 1 or more kinds of transition metals selected from a), LiNi _x M _y Mn ₂ O _{-xy 4 (0 <x <1,} 0 <y <1, 0 <x + y <1, M is Fe, Cr, Co, Zr, Zn, V, at least one selected from the group consisting of Cu-transition metal), LiM _x Mn _{1 x} PO ₄ (0 < x < 1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, V and Cu) and LiM _x Co _{1 -x} PO ₄ 1, and M is at least one transition metal selected from the group consisting of Ni, Fe, Cr, Co, Zr, Zn, V and Cu), a lithium secondary battery comprising a cathode, a separator, In the electrolyte solution,
Non-aqueous organic solvent;
Lithium salts; And
And an electrolyte additive comprising fluorine,
The electrolyte additive is contained in the electrolytic solution in an amount of 0.01 to 3 wt%
Wherein the lithium salt is contained in the electrolytic solution at a concentration of 0.1 to 3M.
The electrolyte solution of a lithium secondary battery according to claim 1, wherein the electrolyte additive comprises LiF.
3. The method of claim 2, wherein the electrolyte additive further comprises 3,5-bis (trifluoromethyl) pyrazole,
Wherein the electrolyte additive is a mixture of the LiF and the 3,5-bis (trifluoromethyl) -pyrazole in a weight ratio of 1: 0.1-10.
The lithium secondary battery according to claim 1,
Wherein the electrolyte layer is made of at least one material selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ .
The method according to claim 1, wherein the non-
Ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 0.1-10.
The ionic liquid according to claim 1, wherein the electrolytic solution further comprises an ionic liquid, wherein the ionic liquid is contained in an amount of 0.01 to 60 wt%
The ionic liquid is a substance in which a cation and an anion are paired and is liquid at ordinary temperature,
Wherein the cation comprises at least one material selected from the group consisting of piperidinium, pyrolidinium and imidazolium,
The anion may be selected from the group consisting of bis (trifluoromethylsulfonyl) imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ) and bis (fluorosulfonyl) imide (Bis (fluorosulfonyl) imide). &Lt; / RTI &gt;
The method of claim 1, wherein the electrolyte is selected from the group consisting of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-propyl-piperidinium bis Methyl-ethyl-pyrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide ), Methyl-propyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium bis (fluorosulfonyl) imide methyl-ethyl-piperidinium bis (fluorosulfonyl) imide, methyl-propyl-piperidinium bis (fluorosulfonyl) imide, methyl-ethyl-pyrrolidinium bis Methyl-ethyl-pyrolidinium bis (fluorosulfonyl) imide) and methyl -Propyl-pyrrolidinium bis (fluorosulfonyl) imide, wherein the ionic liquid is added to the electrolytic solution in an amount of 0.01 - By weight based on the total weight of the lithium secondary battery.
_{LiM x Mn 2 -x O 4 (} 0 <x <1, M is Ni, Fe, Cr, Co, Zr, Zn, V, Cu 1 or more kinds of transition metals selected from a), LiNi _x M _y Mn ₂ O _{-xy 4 (0 <x <1,} 0 <y <1, 0 <x + y <1, M is Fe, Cr, Co, Zr, Zn, V, at least one selected from the group consisting of Cu-transition metal), LiM _x Mn _{1 x} PO ₄ (0 < x < 1, M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, V and Cu) and LiM _x Co _{1 -x} PO ₄ 1 and M is at least one transition metal selected from Ni, Fe, Cr, Co, Zr, Zn, V and Cu);
An anode including a negative active material capable of inserting or removing lithium ions;
A separation membrane for preventing a short circuit between the anode and the cathode; And
And an electrolyte solution in which a lithium salt is dissolved between the positive electrode and the negative electrode,
The electrolyte solution,
Non-aqueous organic solvent;
Lithium salts; And
And an electrolyte additive comprising fluorine,
The electrolyte additive is contained in the electrolytic solution in an amount of 0.01 to 3 wt%
Wherein the lithium salt is contained in the electrolytic solution at a concentration of 0.1 to 3M.
The lithium secondary battery according to claim 8, wherein the electrolyte additive comprises LiF.
The method of claim 9, wherein the electrolyte additive further comprises 3,5-bis (trifluoromethyl) -pyrazole,
Wherein the electrolyte additive is a mixture of the LiF and the 3,5-bis (trifluoromethyl) pyrazole in a weight ratio of 1: 0.1 to 10.
The lithium secondary battery according to claim 8,
Wherein at least one material selected from LiPF ₆ , LiBF ₄ , LiClO ₄ , Li (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ is used.
9. The method according to claim 8, wherein the non-
Ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 1: 0.1-10.
The ionic liquid according to claim 8, wherein the electrolytic solution further comprises an ionic liquid, wherein the ionic liquid is contained in an amount of 0.01 to 60 wt%
The ionic liquid is a substance in which a cation and an anion are paired and is liquid at ordinary temperature,
Wherein the cation comprises at least one material selected from the group consisting of piperidinium, pyrolidinium and imidazolium,
The anion may be selected from the group consisting of bis (trifluoromethylsulfonyl) imide, tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ) and bis (fluorosulfonyl) imide (Bis (fluorosulfonyl) imide). &Lt; / RTI &gt;
The method of claim 8, wherein the electrolyte is selected from the group consisting of methyl-ethyl-piperidinium bis (trifluoromethylsulfonyl) imide, methyl-propyl-piperidinium bis Methyl-ethyl-pyrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide ), Methyl-propyl-pyrrolidinium bis (trifluoromethylsulfonyl) imide, methyl-ethyl-piperidinium bis (fluorosulfonyl) imide methyl-ethyl-piperidinium bis (fluorosulfonyl) imide, methyl-propyl-piperidinium bis (fluorosulfonyl) imide, methyl-ethyl-pyrrolidinium bis Methyl-ethyl-pyrolidinium bis (fluorosulfonyl) imide) and methyl -Propyl-pyrrolidinium bis (fluorosulfonyl) imide, wherein the ionic liquid is added to the electrolytic solution in an amount of 0.01 - By weight based on the total weight of the lithium secondary battery.

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