KR20150079078A - Non-aqueous electrolyte for lithium ion battery containing silyl ether and lithium ion battery including the same - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte for a lithium secondary battery containing silyl ether and a lithium secondary battery including the same. The non-aqueous electrolyte for a lithium secondary battery of the present invention contains a silyl ether compound represented by formula 1. In formula 1, R_1, R_2, R_3, R_4, and R_5 are each independently an alkyl group or an aryl group having hydrogen or carbon atoms 1 to 10. According to the present invention, it is possible to lengthen a life of a battery by preventing decomposition of a lithium salt, generation of a gas, and dissolution of an electrode.

Description

TECHNICAL FIELD [0001] The present invention relates to a non-aqueous electrolyte for a lithium secondary battery containing a silyl ether, and a lithium secondary battery comprising the lithium secondary battery. [0002]

The present invention relates to a nonaqueous electrolyte for a lithium secondary battery containing a silyl ether and a lithium secondary battery comprising the same.

As mobile phones, camcorders, notebook PCs, and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specific. The electrochemical device is one of the most remarkable fields in this respect, and development of a rechargeable secondary battery has become a focus of attention.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s is a battery in which charging and discharging are repeated as lithium ions are inserted and removed from the positive electrode and the negative electrode, and the chemical energy can be converted into electrical energy through the oxidation- have.

The electrolytic solution is generally prepared by using a carbonate-based organic solvent such as ethylene carbonate or dimethyl carbonate as an electrolyte solvent and using a lithium salt such as LiPF ₆ or LiBF ₄ as an electrolyte salt. LiPF ₆ , The fluorine-based lithium salt such as LiBF ₄ has an advantage that it is advantageous to obtain a high capacity and a high voltage, but it has a problem that the performance of the battery is deteriorated due to a very sensitive reaction with moisture. That is, the fluorine-based lithium salt reacts with moisture present in the battery or in the battery to form hydrofluoric acid, which may cause the following problems.

Generally, the SEI film formed on the surface of the anode by the reaction of the carbonate-based organic solvent with the lithium ion in the electrolytic solution during the initial charging of the tooth cell allows only lithium ions to pass therethrough and prevents the electrolyte solvent having a large molecular weight from being co- And serves as a protective film for preventing destruction of the negative electrode structure. The SEI film prevents contact between the electrolyte solution and the negative electrode, thereby minimizing the decomposition of the electrolyte solution and the reduction of the reversible lithium amount. However, such an SEI film is highly reactive with HX (X = F, Cl, Br, I) present in the cell and can be easily destroyed, which may lead to continuous regeneration of the SEI film, resulting in a decrease in the capacity of the cell. Also, due to the decomposition of the organic solvent of the carbonate during the regeneration process of the SEI film, gases such as CO, CO ₂ , CH ₄ , and C ₂ H ₆ are generated, and the stability and lifetime characteristics of the battery may be deteriorated.

Korean Patent Publication No. 10-2008-0110404

The present invention provides an electrolyte for a lithium secondary battery having excellent stability and life characteristics of a lithium secondary battery.

One aspect of the present invention may be a nonaqueous electrolyte solution for a lithium secondary battery comprising a silyl ether compound represented by the general formula (1)

≪ Formula 1 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or an aryl group.

The alkyl group having 1 to 10 carbon atoms may be an alkyl group in which a part or all of the alkyl group is substituted with halogen.

The silyl ether compound is preferably selected from 4- (trimethylsiloxy) -3-penten-2-one, 4- (triethylsiloxy) 2- (4- (tripropylsiloxy) -3-penten-2-one), 4- (triphenylsiloxy) - (tributylsiloxy) -3-penten-2-one).

The non-aqueous electrolyte solution of this aspect may further include a non-aqueous organic solvent containing at least one selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based organic solvents.

The content of the silyl ether compound may be 0.1 to 10% by weight based on the total weight of the electrolytic solution.

The non-aqueous liquid electrolyte of the present _{aspect, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiClO 4, LiCF 3 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiAlO 4, LiAlCl _4, and LiSO ₃ CF _{3. The} lithium salt may further include at least one selected from the group consisting of LiAlCl ₄ and LiSO ₃ CF ₃ .

The concentration of the lithium salt in the electrolytic solution may be 0.8 to 2.0 M.

Another aspect of the present invention may be a lithium secondary battery comprising the non-aqueous electrolyte.

When the silyl ether is added to the electrolyte of the lithium secondary battery according to the present invention, the silicon-oxygen bond existing in the silyl ether reacts with moisture or hydrofluoric acid in the electrolytic solution to decrease the concentration of water or hydrofluoric acid, This excellent SEI film can be formed. Further, it is possible to prevent the decomposition of the lithium salt, the generation of gas, and the dissolution of the electrode, thereby improving the lifetime of the battery.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The lithium secondary battery basically includes a cathode, a cathode (anode) and an electrolytic solution. The electrolyte solution may be a lithium salt dissolved in a non-aqueous organic solvent. This electrolytic solution performs the function of transferring lithium ions between the positive electrode and the negative electrode. The performance of the lithium secondary battery may be deteriorated due to decomposition of the electrolyte and generation of gas during charging or discharging. Various additives may be added to the electrolyte to prevent the deterioration of the performance of the lithium secondary battery.

One aspect of the present invention may be a non-aqueous electrolyte for a lithium secondary battery comprising a silyl ether compound represented by the general formula (1) as an additive.

≪ Formula 1 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or an aryl group.

The alkyl group having 1 to 10 carbon atoms may be an alkyl group in which a part or all of the alkyl group is substituted with halogen.

Examples of the silyl ether compound represented by the formula (1) include 4- (trimethylsiloxy) -3-penten-2-one, 4- (triethylsiloxy) -3 3-penten-2-one, 4- (tripropylsiloxy) -3-penten-2- -one), 4- (tributylsiloxy) -3-penten-2-one, and the like.

The content of the silyl ether compound may be 0.1 to 10% by weight based on the total amount of the electrolytic solution. When the content of the silyl ether compound is less than 0.1% by weight, the effect of improving the lifespan property due to the addition of the silyl ether compound is insignificant. When the content is more than 10% by weight, the viscosity of the electrolyte is large, have.

The electrolytic solution of this aspect may further include a non-aqueous organic solvent. As the non-aqueous organic solvent, at least one selected from the group consisting of a carbonate-based, ester-based, ether-based, and ketone-based organic solvent may be used. But are not limited to, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC) (NMP), ethylmethyl carbonate (EMC), butyrolactone, gamma butyrolactone (GBL), valerolactone, diethyl ether, Caprolactone, fluoroethylene carbonate (FEC), methyl formate, ethyl formate, formate propionate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, Or a mixture of two or more of them may be used.

The electrolytic solution of this aspect may further include a lithium salt, and as such a lithium salt, a material widely used generally in a lithium secondary battery can be used. Specifically, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , ₃ at least one element selected from the group consisting of CF ₃ may be used.

The concentration of the lithium salt in the electrolytic solution is preferably 0.8 to 2.0 M. If it is less than 0.8 M, the lithium ion concentration may be low and the performance of the battery may be deteriorated. When the electrolyte concentration exceeds 2 M, the viscosity of the electrolyte may be large and the ion conductivity in the battery may be rather reduced.

Another aspect of the present invention may be a lithium secondary battery comprising the electrolyte solution. The positive electrode and the negative electrode of the lithium secondary battery can be manufactured using a generally known active material. A slurry is prepared by mixing an active material, a binder, and a conductive agent with a solvent, applying the slurry to a collector such as aluminum, drying and pressing the slurry to produce a positive electrode and a negative electrode.

As the cathode active material, a lithium composite oxide such as LiM _x O ₂ (M is at least one transition metal represented by Co, Ni, Mn, Fe, Al, V, Ti and the like and x is usually 0.05 or more and 1.10 or less) have. The transition metal (M) is preferably Co, Ni or Mn. Specifically, LiCoO ₂ , LiNiO ₂ , LiNi _y Co _{1 -y} O ₂ (0 <y <1), LiMn ₂ O ₄ Etc. may be used. The positive electrode active material is Li _x Fe _{1 -} y M _y PO ₄ where M is one or more of Mn, Cr, V, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, x is 0.05 to 1.2, and y is 0 to 0.8). Specific examples thereof include LiFePO ₄ . In addition, TiS ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ Or a metal oxide may also be used as a cathode active material.

As the negative electrode active material, natural graphite, artificial graphite, carbon fiber, coke, carbon black, activated carbon, lithium metal, lithium alloy and the like can be used. The anode active material, the binder, and the conductive agent are mixed with a solvent to form a slurry, which is applied to an anode current collector, followed by drying and pressing to produce a cathode.

The binder serves to bind the active material and the conductive agent to bind to the current collector, and binds lithium ions such as polyvinylidene fluoride, polypropylene, carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polyvinyl alcohol Those conventionally used in a secondary battery can be used.

Conductive agents such as artificial graphite, natural graphite, acetylene black, ketjen black, channel black, lamp black, thermal black, conductive fibers such as carbon fiber and metal fiber, conductive metal oxides such as titanium oxide, metal powders such as aluminum and nickel Can be used.

The separator may also include a separator, which is a porous membrane between the anode and the cathode that prevents electrical shorting between the two electrodes and serves as a pathway for ion transport. The separator may be a composite of a single olefin or olefin such as polyethylene (PE) and polypropylene (PP), a polyamide (PA), a polyacrylonitrile (PAN), a polyethylene oxide (PEO), a polypropylene oxide Glycol diacrylate (PEGA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC) and the like can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example

Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate were mixed at a volume ratio of 20:40:40 to prepare an organic solvent. Next, LiPF ₆ was dissolved in an organic solvent as a lithium salt to prepare a non-aqueous electrolyte solution having a lithium salt concentration of 1 M. Then, 4- (trimethylsiloxy) -3-pentene-2-one was added to the electrolytic solution to which the lithium salt was added. The content of 4- (trimethylsiloxy) -3-penten-2-one was 1.0% by weight in the total electrolytic solution.

The _{LiNi 0 .5 Co 0 .2 Mn 0} .3 O 2 as the positive electrode, the artificial graphite as a negative electrode, a porous polyethylene film separator, an electrolytic solution was prepared a coin cell using the non-aqueous electrolyte.

Comparative Example

A coin cell was produced in the same manner as in Example 1, except that an electrolyte solution containing no additive was used.

Evaluation of battery life characteristics

The coin cells prepared in Examples and Comparative Examples were charged at a constant voltage / constant current of 4.2 V and 1 C-rate at 25 캜 and 60 캜, respectively, and subjected to constant current discharging 100 times and 50 times at a rate of 1 C- , And the results are shown in Table 1.

Content of additive (% by weight) Life characteristics (capacity ratio (%)) 25 ° C, 100 times 60 ° C, 50 times Comparative Example 0 64.0 70.6 Example One 83.8 84.8

In Table 1, the capacity ratio (%) means the ratio of capacity after 100 cycles or 50 cycles after charge / discharge in one charge / discharge cycle. Referring to Table 1, it can be seen that the life characteristics of the battery are improved by adding a silyl ether additive to the electrolyte solution.

The terms used in the present invention are intended to illustrate specific embodiments and are not intended to limit the invention. The singular presentation should be understood to include plural meanings, unless the context clearly indicates otherwise. The word "comprises" or "having" means that there is a feature, a number, a step, an operation, an element, or a combination thereof described in the specification. The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

Claims (8)

A non-aqueous electrolyte solution for a lithium secondary battery comprising a silyl ether compound represented by formula (1)
&Lt; Formula 1 >

Here, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or an aryl group.
The method according to claim 1,
Wherein the alkyl group having 1 to 10 carbon atoms is an alkyl group partially or wholly substituted with halogen.
The method according to claim 1,
The silyl ether compound may be selected from the group consisting of 4- (trimethylsiloxy) -3-penten-2-one, 4- (triethylsiloxy) 2- (4- (tripropylsiloxy) -3-penten-2-one), 4- (triphenylsiloxy) - (tributylsiloxy) -3-penten-2-one). The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1,
The method according to claim 1,
Wherein the non-aqueous organic solvent further comprises at least one selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based organic solvents.
5. The method of claim 4,
Wherein the content of the silyl ether compound is 0.1 to 10% by weight based on the total weight of the electrolytic solution.
The method according to claim 1,
Further comprising a lithium salt, the lithium salt is _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiClO 4, LiCF 3 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2 , LiAlO ₄ , LiAlCl _4, and LiSO ₃ CF _{3. The} nonaqueous electrolyte solution for a lithium secondary battery according to claim 1,
The method according to claim 6,
Wherein the concentration of the lithium salt in the electrolytic solution is 0.8 to 2.0 M.
A lithium secondary battery comprising the nonaqueous electrolyte according to any one of claims 1 to 7.