KR102096068B1 - Non-aqueous electrolyte for lithium ion battery containing silyl ether and lithium ion battery including the same - Google Patents

Abstract

여기서, R₁, R₂, R₃, R₄ 및 R₅는 각각 독립적으로 수소, 탄소수 1 내지 10 의 알킬기이거나 또는 아릴기다. 본 발명에 의하면 리튬염의 분해, 가스의 발생 및 전극의 용해를 방지하여 전지의 수명을 향상시킬 수 있다.The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery containing silyl ether and a lithium secondary battery comprising the same. The non-aqueous electrolyte solution for a lithium secondary battery according to the present invention is characterized by including a silyl ether compound represented by the following Chemical Formula 1.
<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. According to the present invention, it is possible to improve the life of the battery by preventing decomposition of lithium salt, generation of gas, and dissolution of the electrode.

Description

Non-aqueous electrolyte solution for lithium secondary batteries containing silyl ether and lithium secondary batteries comprising the same

The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery containing silyl ether and a lithium secondary battery comprising the same.

As the field of application extends to mobile phones, camcorders, notebook PCs, and even electric vehicles, efforts to research and develop electrochemical devices are becoming more concrete. The electrochemical device is the most attracting field in this respect, and among them, the development of a secondary battery capable of charging and discharging has become a focus of attention.

Among the currently applied secondary batteries, the lithium secondary batteries developed in the early 1990s are batteries in which charging and discharging are repeated as lithium ions are inserted and removed at the positive and negative electrodes, and can convert chemical energy into electrical energy through redox reaction. have.

Electrolyte is generally prepared by using a carbonate-based organic solvent such as ethylene carbonate (Ethylene Carbonate), dimethyl carbonate (DiMethylCarbonate) as an electrolyte solvent, and using lithium salts such as LiPF ₆ and LiBF ₄ as electrolyte salts, LiPF ₆ , The fluorine-based lithium salt such as LiBF ₄ has an advantage of obtaining a high capacity and a high voltage, but reacts very sensitively to moisture, causing a problem in battery performance. That is, the fluorine-based lithium salt may form hydrofluoric acid during the manufacturing process of the battery or by reacting with moisture present in the battery, thereby causing the following problems.

In general, the SEI film formed on the surface of the negative electrode by reacting with lithium ions in the electrolyte when the carbonate-based organic solvent is initially charged during the charging of the dental cell, prevents the electrolyte solvent having a high molecular weight from being intercalated to the negative electrode. It serves as a protective film that prevents destruction of the cathode structure, and the contact between the electrolyte and the cathode is prevented by the SEI film, thereby minimizing the decomposition of the electrolyte and the reduction in the amount of reversible lithium. However, such a SEI membrane can be easily destroyed due to its strong reactivity with HX (X = F, Cl, Br, I) present in the battery, and this leads to continuous regeneration of the SEI membrane, thereby degrading the capacity of the battery. In addition, during the regeneration process of the SEI film, gases such as CO, CO ₂ , CH ₄ , and C ₂ H ₆ are generated due to decomposition of the carbonate organic solvent, thereby deteriorating the stability and life characteristics of the battery.

Korean Patent Publication No. 10-2008-0110404

The present invention is to provide an electrolyte for a lithium secondary battery excellent in stability and life characteristics of a lithium secondary battery.

One aspect of the present invention may be a non-aqueous electrolyte solution for a lithium secondary battery comprising a silyl ether compound represented by Chemical Formula 1:

<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 alkyl group having 1 to 10 carbon atoms may be an alkyl group partially or completely substituted with halogen.

The silyl ether compound is 4- (trimethylsiloxy) -3-penten-2-one (4- (trimethylsiloxy) -3-penten-2-one), 4- (triethylsiloxy) -3-penten-2- On (4- (triethylsiloxy) -3-penten-2-one), 4- (tripropylsiloxy) -3-penten-2-one (4- (tripropylsiloxy) -3-penten-2-one), 4 It may include one or more selected from the group consisting of-(tributylsiloxy) -3-penten-2-one (4- (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 of the total electrolyte solution.

The non-aqueous electrolyte of this aspect 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 It may further include a lithium salt containing at least one selected from the group consisting of.

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

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

When silyl ether is added to the electrolytic solution of a lithium secondary battery according to the present invention, silicon-oxygen bonds present in the silyl ether react with water or hydrofluoric acid in the electrolytic solution to reduce the concentration of water or hydrofluoric acid, thereby improving thermal stability and lithium ion conductivity. This excellent SEI film can be formed. In addition, it is possible to improve the life of the battery by preventing decomposition of lithium salt, generation of gas, and dissolution of the electrode.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Embodiments of the present invention may be modified in 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 positive electrode (cathode), a negative electrode (anode), and an electrolytic solution. The electrolyte can be used by dissolving a lithium salt in a non-aqueous organic solvent. The electrolyte performs a function of transferring lithium ions between the positive electrode and the negative electrode. During charging or discharging, the performance of the lithium secondary battery may deteriorate due to decomposition of the electrolyte and gas generation, and various additives may be added to the electrolyte to prevent such performance degradation.

One aspect of the present invention may be a non-aqueous electrolyte solution for a lithium secondary battery including a silyl ether compound represented by Chemical Formula 1 as an additive.

<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 alkyl group having 1 to 10 carbon atoms may be an alkyl group partially or completely substituted with halogen.

As the silyl ether compound represented by Chemical Formula 1, 4- (trimethylsiloxy) -3-penten-2one (4- (trimethylsiloxy) -3-penten-2-one), 4- (triethylsiloxy) -3 -Penten-2-one (4- (triethylsiloxy) -3-penten-2-one), 4- (tripropylsiloxy) -3-penten-2-one (4- (tripropylsiloxy) -3-penten-2 One or more selected from the group consisting of -one), 4- (tributylsiloxy) -3-penten-2-one (4- (tributylsiloxy) -3-penten-2-one), and the like can be used.

The content of the silyl ether compound may be 0.1 to 10% by weight in the total electrolyte solution. When the content of the silyl ether compound is less than 0.1% by weight, the effect of improving the life characteristics caused by the addition of the silyl ether compound is insignificant. have.

The non-aqueous organic solvent may be further included in the electrolytic solution of this aspect, and as the non-aqueous organic solvent, one or more selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based organic solvents may be used. Without being limited thereto, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), dimethyl sulfoxide, aceto Nitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), butyrolactone, gamma-butyrolactone (GBL), valerolactone, Caprolactone, fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate or halogen derivatives thereof Or may be used by mixing two or more.

Lithium salt may be further included in the electrolytic solution of this aspect, and a material widely used in lithium secondary batteries may be used as the lithium salt. 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 and LiSO One or more selected from the group consisting of ₃ CF ₃ may be used.

The concentration of lithium salt in the electrolyte is preferably 0.8 to 2.0 M. If the concentration is less than 0.8 M, the performance of the battery may be low due to a low concentration of lithium ions. When the concentration exceeds 2 M, the viscosity of the electrolyte may be large, so that the ion conductivity in the battery may decrease.

Another aspect of the present invention may be a lithium secondary battery containing the electrolyte. As a positive electrode and a negative electrode of a lithium secondary battery, a known active material can be used. A positive electrode and a negative electrode may be prepared by mixing an active material, a binder, and a conductive agent with a solvent to prepare a slurry, and applying the slurry to a current collector such as aluminum, followed by drying and pressing.

As the positive electrode active material, LiM _x O ₂ (M is Co, Ni, Mn, Fe, Al, V, Ti, etc., which represents one or more transition metals, and x is usually 0.05 or more and 1.10 or less) lithium composite oxide or the like can be used. have. Co, Ni, and Mn are preferable as the transition metal (M). Specifically, LiCoO ₂ , LiNiO ₂ , LiNi _y Co _{1 -y} O ₂ (0 <y <1), LiMn ₂ O ₄ Etc. can be used. In addition, as a positive electrode active material Li _x Fe _{1 -} yM _y PO ₄ (M is one or more of Mn, Cr, V, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B and Nb, x is 0.05 to 1.2, and y is 0 to 0.8) may be used, and specifically, LiFePO ₄ may be used. In addition, TiS ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ Metal oxides or metal oxides, such as, can also be used as the anode active paper.

As the negative electrode active material, natural graphite, artificial graphite, carbon fiber, coke, carbon black, activated carbon, lithium metal or lithium alloy may be used. A negative electrode can be prepared by mixing a negative electrode active material, a binder, and a conductive agent with a solvent to form a slurry, applying it to a negative electrode current collector, followed by drying and pressing.

The binder serves to fix the current collector by binding an active material and a conductive agent, and lithium ions such as polyvinylidene fluoride, polypropylene, carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, and polyvinyl alcohol Those commonly used in secondary batteries can be used.

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

In addition, a separator may be included, and the separator is a porous membrane existing between an anode and a cathode to prevent electrical short circuit between two electrodes and function as a channel for ion transfer. As the separator, a single olefin or a complex of olefins such as polyethylene (PE) and polypropylene (PP), polyamide (PA), polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene 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

An organic solvent was prepared by mixing ethylene carbonate (Ethylene Carbonate), ethyl methyl carbonate (Dithethyl Carbonate) and dimethyl carbonate (DiMethyl Carbonate) in a volume ratio of 20:40:40. Next, LiPF ₆ was dissolved in a lithium salt in an organic solvent to prepare a non-aqueous electrolyte having a lithium salt concentration of 1M. Next, 4- (trimethylsiloxy) -3-penten-2-one (4- (trimethylsiloxy) -3-pentene-2-one) was added to the electrolyte 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 electrolyte 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 manufactured according to the same method as in Example, except that an electrolyte solution without an additive was used.

Evaluation of battery life characteristics

After 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 ° C. and 60 ° C., constant current discharge to 2.8 V at 1 C-rate was performed 100 times and 50 times. , Table 1 shows the results.

Additive content (% by weight) Life characteristics (capacity ratio (%)) 25 ℃, 100 times 60 ℃, 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 the capacity after 100 charges or 50 charges / discharges compared to the capacity at one charge / discharge. Referring to Table 1, the Examples show that the capacity ratio is significantly better after the life test than the comparative example, from which it can be confirmed that the life characteristics of the battery were improved by adding a silyl ether additive to the electrolyte.

The terms used in the present invention are intended to describe specific embodiments, and are not intended to limit the present invention. Singular expressions should be considered to include plural meanings, unless the context is clear. The terms "include" or "have" mean that there are features, numbers, steps, actions, elements, or combinations thereof described in the specification, but are not intended to exclude them. The present invention is not limited by the above-described embodiment and the accompanying drawings, and is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and modification will be possible by those skilled in the art without departing from the technical spirit of the present invention as set forth in the claims, and this also belongs to the scope of the present invention. something to do.

Claims (8)

A non-aqueous electrolyte solution for a lithium secondary battery comprising a silyl ether compound represented by Chemical Formula 1:
<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.
According to claim 1,
The non-aqueous electrolyte solution for a lithium secondary battery, wherein the alkyl group having 1 to 10 carbon atoms is an alkyl group partially or entirely substituted with halogen.
According to claim 1,
The silyl ether compound is 4- (trimethylsiloxy) -3-penten-2one (4- (trimethylsiloxy) -3-penten-2-one), 4- (triethylsiloxy) -3-pentene-2- On (4- (triethylsiloxy) -3-penten-2-one), 4- (tripropylsiloxy) -3-penten-2-one (4- (tripropylsiloxy) -3-penten-2-one), 4 -(Tributylsiloxy) -3-penten-2-one (4- (tributylsiloxy) -3-penten-2-one) Non-aqueous electrolyte for lithium secondary batteries containing at least one member selected from the group consisting of.
According to claim 1,
A non-aqueous electrolyte solution for a lithium secondary battery, further comprising a non-aqueous organic solvent, wherein the non-aqueous organic solvent comprises one or more selected from the group consisting of carbonate-based, ester-based, ether-based and ketone-based organic solvents.
According to claim 4,
The content of the silyl ether compound is a non-aqueous electrolyte solution for a lithium secondary battery of 0.1 to 10% by weight of the total electrolyte solution.
According to claim 1,
Lithium salt further comprises, 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 Non-} aqueous electrolyte for a lithium secondary battery comprising at least one member selected from the group consisting of.
The method of claim 6,
The non-aqueous electrolyte for lithium secondary batteries having a concentration of lithium salt in the electrolyte of 0.8 to 2.0 M.
A lithium secondary battery comprising the non-aqueous electrolyte of any one of claims 1 to 7.