KR100406081B1 - Ion conductive organic compound, electrolytes compositions containing said compound, and lithium secondary battery formed by the said compositions - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid electrolytes, which are components of electrolytes used in batteries, in particular lithium secondary batteries, and more particularly to ion conductive organic compounds as organic solvents or plasticizers used in electrolytes. The present invention also relates to a liquid electrolyte and a polymer electrolyte prepared by using the novel ion conductive organic compound, and a lithium secondary battery prepared by the electrolyte.

The ion conductive organic compound according to the present invention has the following structure.

(In the above formula

X ^a is , Alkyl, or-(CO) OX ^b )

Description

Ion conductive organic compound, electrolytes containing said said compound, and lithium secondary battery formed by the said compositions}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid electrolytes, which are components of electrolytes used in batteries, in particular lithium secondary batteries, and more particularly to ion conductive organic compounds as organic solvents or plasticizers used in electrolytes. The present invention also relates to a liquid electrolyte and a polymer electrolyte prepared by using the novel ion conductive organic compound, and a lithium secondary battery prepared by the electrolyte.

Currently, in the case of electrolytes used in materials of secondary batteries, various sensors, and electronic devices, many parts are composed of liquid electrolytes based on ionic conductivity, which is one of characteristics required for each sector. However, many of the existing liquid electrolyte compositions are composed of volatile solvents having low boiling points, which poses a problem of stability. For example, a liquid electrolyte for a lithium secondary battery uses ethylene carbonate (EC), which is an aprotic cyclic polar solvent, as a quantum solvent to dissociate lithium salts, and dimethyl carbonate (DMC), which is a low viscosity non-hydrogen solvent. ), Diethyl carbonate (DEC) is used to control the ionic conductivity by adjusting the viscosity of the electrolyte, but in this case, the boiling point of DMC is 90 ℃, and the boiling point of DEC is 126-128 ℃. Changes in the environment increase the internal pressure of the battery, increase the temperature of the operating device, leak the electrolyte, and pose a risk of explosion.

In order to compensate for this problem, many secondary battery manufacturing processes are manufactured by combining polymer and liquid electrolyte and delaying leakage as much as possible. However, these polymer electrolytes use existing liquid electrolytes as they are, so it is difficult to fundamentally solve the problem of stability.

As another composition and manufacturing process of the polymer electrolyte for secondary batteries, there is a method of putting together a liquid electrolyte and a matrix polymer to dissolve by applying heat, and then applying the film on an electrode. However, this process is difficult to apply because it is difficult to uniformly control the composition of the volatile solvents used in the composition of the liquid electrolyte in the process of mixing melting by applying heat. Thus, cosolvents used with EC in these processes require conditions of non-volatile, electrochemical stability and high dielectric constant (polarity). However, in the case of using propylene carbonate (PC) as an actual example, the process problem is overcome, but the efficiency of the negative electrode carbon anode is reduced (Arakawa et al., J, Electronal. Chem. 219: 273-280, 1987). , Shu et al., J. Electrochem. Soc. 140: 922-927, 1993).

On the other hand, in the development of pure polymer electrolytes, various types of copolymers have been studied mainly by using polyethylene oxide (PEO) derivatives, but the polarity decreases as the chain length increases due to the nature of the polymer chain. In the short case, the mechanical properties are reduced. In order to overcome this problem, researchers such as Abraham (quotation) used PEO-based oligomers as plasticizers to improve ionic conductivity of polymer electrolytes. However, in the case of mainly used PEO oligomers, in the case of PEG having a molecular weight of 200-1000 g / mol, hydroxy groups of the end groups react with lithium to form lithium hydroxide, which interferes with electrochemical stability. That is, the plasticizer in the pure polymer electrolyte is preferably a polar oligomer of the electrochemically stable form.

The present invention is to solve the shortcomings of the conventional electrolyte as described above, the purpose is to prepare a novel ion conductive organic solvent (or plasticizer) having a high polarity, excellent ionic conductivity, high boiling point liquid electrolyte or polymer electrolyte The present invention is to provide a lithium secondary battery employing the prepared liquid or polymer electrolyte.

1 is measured by varying the concentration of LiClO ₄ for 1Kg of the ion conductive organic compound according to the present invention and the comparative example (organic substance substituted with -cyclic cyclic OH at the end of the conventional organic solvent polyethylene glycol (PEG)) One ion conductivity is shown.

Figure 2 shows the change in dielectric constant (polarity) of the ion conductive organic compound according to the present invention, the conventional organic solvent PEG, and the organic material substituted with -cyclic cyclic carbonate at the PEG end.

The ion conductive organic compound of the present invention for achieving the above object is represented by the following general formula (1) used for dissociating inorganic salts or transferring ions.

(In the above formula

X ^a is , Alkyl, or-(CO) OX ^b ,

X ^b is hydrogen, alkyl, aryl, alkenyl, fluorine, or fluorinated low alkyl,

Y, Z is hydrogen, fluorine, alkyl, aryl, alkenyl, or

-(C _α P _2α ) _r- (C _β P _2β O _{β / t} ) _s -OX ^a

P is hydrogen, fluorine, or 1/2 hydrogen fluoride

j, k, l, m, p, q, α, β, r, s are 0 to 10

t, n is 1 to 10)

In the ion conductive organic compound according to the present invention, the alkyl of the formula is a branched or unbranched saturated hydrocarbon structure, the length is 1-10 carbons (methyl, ethyl), normal-propyl, isopropyl, etc.), Fluorinated lower alkyl has an alkyl structure of 1-6 carbons, at least one hydrogen position is substituted by fluorine, and aryl represents an aromatic consisting of 5-7 carbons, and one or more Hydrogen is also substituted with other elements, and alkenyl is a branched or unbranched hydrocarbon structure having a length of 2-12 carbons and having one or more double bonds.

In the present invention ion-conductive organic compound according to, X ^a in the formula is Y, depending on the type of Z it is possible to configure a one to four-terminal, and in this case have one of the three functional groups as possible to the X ^a It can be characterized by being capable of constituting all the end groups alone depending on the form of Y, Z.

The organic liquid electrolyte composition according to the present invention is characterized by containing the ion conductive organic compound represented by the formula (1) in an amount of 5% by weight to 100% by weight relative to the total weight of the organic liquid electrolyte composition.

The organic liquid electrolyte composition according to the present invention is characterized in that an inorganic salt is added in an amount of 0.1M to 1.5M with respect to the ion conductive organic compound, and the organic compound can be used together with an organic electrolyte solution that is conventionally used.

The polymer electrolyte composition according to the present invention is a polymer electrolyte composition in a gel or hybrid form prepared by complexing the ion conductive organic compound represented by Formula 1 with a polymer, wherein the ion conductive organic compound is added to the total weight of the polymer electrolyte composition. It is characterized by containing in an amount of 5% by weight to 90% by weight.

In the polymer electrolyte composition according to the present invention, when the polymer has the ability to dissociate an inorganic salt, the ion conductive organic compound may help dissociation of the inorganic salt to control ion conductivity or to control mechanical properties of the polymer. do.

The lithium secondary battery according to the present invention is manufactured using the organic liquid electrolyte or the polymer electrolyte composition.

The ion conductive organic compound of the structure of Formula 1 according to the present invention is applied to an organic liquid electrolyte composition.

The organic liquid electrolyte composition according to the present invention is composed of the ion conductive organic compound and a lithium salt. In the case of the liquid electrolyte composition, in order to improve the dissociation of ions and to facilitate the conduction of ions, organic solvents have to have high dielectric constant (polarity) and low reactivity with lithium metal. It is preferable to use two or more mixed solutions composed of a solvent having a low dielectric constant and a solvent having a low viscosity. In addition, it is preferable to use a lithium salt having a small lattice energy, a large dissociation degree, excellent ion conductivity, and good thermal stability and oxidation resistance. Examples of lithium salts include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO _3, LiN (CF ₃ SO ₂ ) ₂ , LiSCN, LiC (CF ₃ SO ₂ ) ₃ , and the like, and optional mixtures thereof may be used. have. Preferred concentrations of the lithium salt are 0.4M to 1.5M.

In the above organic liquid electrolyte composition, it is preferable that the ion conductive organic compound according to the present invention is contained in an amount of 5% by weight to 100% by weight based on the total weight of the total composition.

The polymer electrolyte composition according to the present invention is prepared from the ion conductive organic compound.

The polymer electrolyte is generally classified into a hybrid polymer electrolyte or a gel polymer electrolyte prepared by adding an electrolyte solution and a polymer electrolyte which does not contain an organic electrolyte. The ion conductive organic compound according to the present invention may be classified into an electrolyte solution of a hybrid or gel polymer electrolyte. It can be used as a composition. On the other hand, the ion conductive organic compound according to the present invention can be applied to the polymer electrolyte composition by performing a role as a plasticizer, while at the same time serves as a plasticizer in the polymer electrolyte does not contain an organic electrolyte solution.

In addition, the ion conductive organic compound according to the present invention may be used as a composition of a capacitor, a fuel cell, various sensors, and other ion conductive mechanisms, as well as serving as an electrolyte composition of a secondary battery.

Hereinafter, Examples and Experimental Examples will be described in detail with respect to the organic synthesis method of the ion conductive organic compound according to the present invention and the organic liquid electrolyte and the polymer electrolyte to which it is applied. However, these Examples and Experimental Examples are for illustrating the present invention and do not limit the content of the present invention.

<Example 1>

This embodiment is an organic synthesis method of an ion conductive organic compound (hereinafter referred to as Di-CC-Bu) having the structure of Chemical Formula 2, and has three organic synthesis steps. In the first step, 1,4-dibrobobuthane (1,4-dibrobobuthane, 21.6 g, 0.1 mol), 2,2-dimethyl-1,3-dioxolane-4-methanol (2,2-dimethyl-1, 3-dioxolane-4-methanol, 39.6 g, 0.3 mol), sodium hydride (8.4 g, 0.35 mol) and 1,4-dioxane (1,4-dioxane, 250 ml) at 80 ° C. for 3 hours After filtration, the solvent was extracted with water and methylene chloride (CH ₂ Cl ₂ ), and then CH ₂ Cl ₂ was removed. The two-step reaction is obtained by refluxing with the first step product (31.8g, 0.1mol), hydrochloric acid (31.2g) to make dioxolane as dialcohol, and then extract the water with CH ₂ Cl ₂ and remove the water. In the final step, a small amount of Na was added to the resultant (23.8g, 0.1mol) and dimethyl carbonate (27g, 0.3mol) and refluxed for 3 hours, followed by distillation under reduced pressure. The NMR results of the obtained compound are as follows.

¹ H-NMR: 1.6 (4H, -CH ₂ C H ₂ C H ₂ CH _2- ), 3.5 (4H, -OC H ₂ CH _2- ), 3.7 (4H,> CH-C H ₂ -O-) , 4.4, 4.5 (4H, -OC H ₂ -CH <), 4.8 (4H, -CH ₂ -C H <)

<Example 2>

An ion conductive organic compound (hereinafter, referred to as Tri-CC) having a structure of Formula 3 was prepared by the same synthesis method as in Example 1.

Comparative Example 1

A comparative example was prepared by substituting the OH end group of polyethylene glycol having a molecular weight of 200, 400, 600 g / mol with cyclic carbonate (denoted Di-CC-200, 400, 600, respectively).

Experimental Example 1

LiClO ₄ 1M was added to 1 Kg of the organic electrolyte solution (organic solvent) prepared in Examples 1, 2, and Comparative Example 1 to measure ion conductivity, and the results are shown in Table 1 below. In addition, the result of ion conductivity measured by changing the concentration of LiClO ₄ is shown in FIG.

Experimental Example 2

Regarding the weight of the organic liquid electrolyte prepared in Example 1, Example 2, and Comparative Example 1, LiClO ₄ 1M was maintained, and 80% by weight, 90% by weight of ethylene carbonate, and 20% by weight of the organic electrolyte, 10, respectively. Ionic conductivity of the organic liquid electrolyte prepared by mixing the wt% was measured, and the results are shown in Table 1 below.

Table 1: Ionic Conductivity of Examples and Comparative Examples Sample name rescue Experiment number Furtherance Ionic Conductivity (S / cm) Example 1 (Di-CC-Bu) Experiment 1 - 1.52 x 10 ^-4 Experiment 2 EC 90% EC 80% 3.47 x 10 ^-3 2.83 x 10 ^-3 Example 2 (Tri-CC) Experiment 1 - 3.94 ×× x 10 ^-4 Experiment 2 EC 90% EC 80% 3.18 x 10 ^-3 3.13 x 10 ^-3 Comparative Example 1 (Di-CC-200, 400, 600) (Comparative Example, 200, 400, 600 denotes the molecular weight of PEG before end group substitution) Experiment 1 200:- 5.13 x 10 ^-5 Experiment 2 200: EC 90% 200: EC 80% 3.32 x 10 ^-3 2.79 x 10 ^-3 Experiment 1 400:- 5.27 x 10 ^-5 Experiment 2 400: EC 90% 400: EC 80% 3.32 x 10 ^-3 2.08 x 10 ^-3 Experiment 1 600:- 9.04 x 10 ^-5 Experiment 2 600: EC 90% 600: EC 80% 3.47 x 10 ^-3 3.24 x 10 ^-3

Experimental Example 3

The dielectric constant (polarity) size of the organic electrolytes prepared in Examples and Comparative Examples was measured, and the results are shown in FIG. 2.

<Example 3>

The organic liquid electrolyte prepared in the same manner as in Experimental Example 2 was melted at 100 ^o C for 10 minutes after stirring using a magnetic stirrer in a beaker at a weight ratio of polyacrylonitrile and 85:15 to prepare a film on a glass plate using a doctor blade. It was. As a result of measuring the ion conductivity of the film prepared above, all showed excellent ion conductivity of 10 ^-3 S / cm or more. Therefore, it was found that the transparent and uniform gel film exhibited excellent properties as a composition of the gel polymer electrolyte.

According to an embodiment of the present invention, the ion conductive organic compound may be used alone as a plasticizer of the polymer electrolyte or as a component of the electrolyte.

The ion conductive organic compound according to the present invention is contained in an amount of 5% to 100% by weight based on the total weight of the organic liquid electrolyte composition, and 5% to 90% by weight relative to the total weight of the polymer electrolyte composition. It may be applied as a component of the composition, and the electrolyte thus prepared may be applied to a lithium secondary battery.

As described above, the ion conductive organic compound according to the present invention is a novel liquid electrolyte (organic solvent) or a plasticizer having high boiling point and excellent ion conductivity as an oligomer having a structure having the same terminal group which can have high polarity. It can be applied to compositions of electrolytes and other types of polymer electrolytes.

The composition of the organic liquid electrolyte and the polymer electrolyte according to the present invention may be used as a material for fuel cells, sensors, and various electronic devices in addition to various secondary batteries including lithium secondary batteries.

Claims (8)

An ion conductive organic compound represented by the following Chemical Formula 1 used for dissociating an inorganic salt or transferring ions. [Formula 1] (In the above formula X ^a is , Alkyl, or-(CO) OX ^b , X ^b is hydrogen, alkyl, aryl, alkenyl, fluorine, or fluorinated low alkyl, Y, Z is hydrogen, fluorine, alkyl, aryl, alkenyl, or -(C _α P _2α ) _r- (C _β P _2β O _{β / t} ) _s -OX ^a P is hydrogen, fluorine, or 1/2 hydrogen fluoride j, k, l, m, p, q, α, β, r, s are 0 to 10 t, n is 1 to 10) The method of claim 1, Alkyl of the above formula is a branched or unbranched saturated hydrocarbon structure, the length is 1-10 carbons, Fluorinated low alkyl has an alkyl structure of 1-6 carbons and at least one hydrogen position is substituted with fluorine, Aryl represents an aromatic consisting of 5-7 carbons, and includes forms in which one or more hydrogens are substituted with other elements, Alkenyl is a branched or unbranched hydrocarbon structure having a length of 2-12 carbons and having one or more double bonds. The method of claim 1, X ^a of the formula may constitute 1 to 4 terminals depending on the form of Y, Z, in which case one of the three functional groups possible as X ^a is alone, depending on the form of Y, Z An ion-conductive organic compound which can comprise a short term. An organic liquid electrolyte composition comprising the ion conductive organic compound represented by Chemical Formula 1 according to claim 1 in an amount of 5% by weight to 100% by weight based on the total weight of the organic liquid electrolyte composition. The method of claim 4, wherein An inorganic salt is added in an amount of 0.1M to 1.5M with respect to the ion conductive organic compound, and the organic liquid electrolyte composition, wherein the organic compound can be used together with an organic electrolyte solution that is used in the past. A polymer electrolyte composition in a gel or hybrid form prepared by complexing an ion conductive organic compound represented by Chemical Formula 1 according to claim 1 with a polymer, A polymer electrolyte composition comprising the ion conductive organic compound in an amount of 5% by weight to 90% by weight relative to the total weight of the polymer electrolyte composition. The method of claim 6, When the polymer has the ability to dissociate an inorganic salt, the ion conductive organic compound may help dissociation of the inorganic salt to control ionic conductivity or to adjust the mechanical properties of the polymer. A lithium secondary battery prepared using the electrolyte composition of claim 4 or 6.