KR102132733B1 - Multi-arm ethylene oxide and propylene oxide group plasticizer for all-solid-state polymer electrolyte and all-solid-state polymer electrolyte composition comprising the same - Google Patents

Abstract

The present invention relates to a hyperbranched ethylene oxide (EO)-propylene oxide (PO) plasticizer for an all-solid-state polymeric electrolyte, and to an all-solid-state polymeric electrolyte composition comprising the same. A semi-interpenetrating polymer network (IPN) type all-solid-state polymeric electrolyte composition comprising the hyperbranched EO-PO plasticizer for an all-solid-state polymeric electrolyte according to the present invention and a crosslinker can remarkably improve ion conductivity by reducing the crystallization of EO groups in the plasticizer at low temperatures (room temperature), and has excellent electrochemical stability and battery features, and thus, may be advantageously used as an all-solid-state polymeric electrolyte for electrochemical devices such as lithium polymer secondary batteries, fuel cells, and the like.

Description

Multi-arm ethylene oxide-propylene oxide plasticizer for all-solid polymer electrolyte, and all-solid polymer electrolyte composition comprising the same {Multi-arm ethylene oxide and propylene oxide group plasticizer for all-solid-state polymer electrolyte and all-solid-state polymer electrolyte composition comprising the same}

The present invention relates to a multi-branched ethylene oxide-propylene oxide plasticizer for an all-solid polymer electrolyte, an all-solid polymer electrolyte composition comprising the same, and a lithium polymer secondary battery and a fuel cell comprising the all-solid polymer electrolyte composition.

Currently, lithium secondary batteries are used not only as power sources for IT devices such as smartphones and laptops that are used in everyday life, but also as transportation power sources such as electric vehicles and large-scale power storage sources such as energy storage systems (ESSs). Is expanding. A lithium secondary battery is an electrochemical device that can store electricity as chemical energy and convert it into electricity when needed, and is composed of four core elements: an anode, a cathode, a separator, and an electrolyte.

In order to minimize safety problems such as explosion of smartphone battery and ignition of laptop battery, many studies have been conducted to use solid electrolytes with greatly improved safety by replacing liquid electrolytes that may have leakage and have high flammability and are highly flammable and explosive. have. Ceramic-based solid electrolytes are fragile and difficult to apply to the battery manufacturing process, and also have many difficulties in commercialization due to high interface resistance with electrodes.

On the other hand, polymer solid electrolytes have the advantages of superior safety compared to liquid electrolytes, various chemical structure designs are possible, and electrolytes can be manufactured in thin films, and are relatively easy to apply to battery manufacturing processes. Therefore, the battery of electronic devices such as laptop computers, digital camcorders, portable game machines, digital cameras, and mobile phones, which are increasing in demand for consumers with high capacity, stability, and miniaturization, is expected to be rapidly replaced by lithium polymer batteries in addition to lithium. Polymer batteries are attracting attention as next-generation batteries because they are expected to be applied to high-capacity lithium secondary batteries such as hybrid electric vehicles.

Since the ion conductivity of poly(ethylene oxide (PEO)-based solid polymer electrolyte (SPE) has been reported (DE Fenton, JM Parker, PV Wright, Polymer, 14 (1973) 589.), Many studies have been conducted to apply PEO-based solid polymer electrolyte to lithium secondary batteries for high energy use. However, it is not yet used as a commercial product. The reason is that the high crystallinity of the PEO-based polymer leads to a rigid structure at room temperature, which inhibits the movement of ions. As another example of the electrolyte, a polyethylene oxide-polystyrene block copolymer electrolyte is known. Such electrolytes have a lot of room for improvement because the mechanical properties do not reach satisfactory levels.

As an efficient method for improving the ionic conductivity of a PEO-based polymer electrolyte, it is known to manufacture a solid polymer electrolyte by polymerizing a precursor mixed with a multi-branch crosslinking agent, an ion conductive plasticizer, a lithium salt, and a radical initiator with heat or light. Through this manufacturing method, a semi-interpenetrating polymer network (IPN) structure in which a plasticizer is entangled in a solid network structure generated by polymerization of a multi-branched crosslinking agent is formed. At this time, the network structure by the crosslinking agent provides mechanical properties to the polymer electrolyte, and the plasticizer imparts ionic conductivity properties. However, when an EO-based linear polymer is used as a plasticizer imparting ion conduction properties, crystallization occurs at a low temperature, and the ion conductivity properties at a low temperature tend to decrease rapidly.

An object of the present invention is to provide a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte having excellent ion conductivity.

Another object of the present invention is to provide a semi-IPN (Interpenetrating Polymer Network) type all-solid polymer electrolyte composition comprising the multi-branched EO-PO plasticizer for the all-solid polymer electrolyte.

Another object of the present invention is to provide an all-solid polymer electrolyte comprising the composition.

Another object of the present invention is to provide a lithium polymer secondary battery comprising the composition.

Another object of the present invention is to provide a fuel cell comprising the composition.

In order to achieve the above object,

The present invention provides a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte represented by the following Chemical Formula 1.

[Formula 1]

In Chemical Formula 1,

x represents the average number of moles of propylene oxide and is from 0.01 to 10; And

y represents the average added mole number of ethylene oxide, and is 0.1 to 15.

In addition, the present invention,

1.0-90.0% by weight of a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte represented by Formula 1;

1.0-90.0 wt% of a multi-branched EO-PO crosslinking agent for an all-solid polymer electrolyte represented by the following Chemical Formula 2;

Lithium salt 1.0-50.0 wt%; And

It provides an all-solid polymer electrolyte composition characterized in that it comprises; 0.1-5.0% by weight of a curing initiator.

[Formula 1]

In Chemical Formula 1,

x represents the average number of moles of propylene oxide and is from 0.01 to 10; And

y represents the average added mole number of ethylene oxide, and is 0.1 to 15.

[Formula 2]

In Chemical Formula 2,

m represents the average number of added moles of propylene oxide, and is from 0.01 to 10; And

n represents the average added mole number of ethylene oxide, and is 0.1 to 15.

Furthermore, the present invention provides an all-solid polymer electrolyte comprising the composition.

In addition, the present invention provides a lithium polymer secondary battery comprising the composition.

Furthermore, the present invention provides a fuel cell comprising the composition.

The semi-IPN (Interpenetrating Polymer Network) type all-solid polymer electrolyte composition containing the multi-branched EO-PO plasticizer and crosslinking agent for the all-solid polymer electrolyte according to the present invention lowers the crystallization of the EO group of the plasticizer even at low temperatures (room temperature). By doing so, not only the ion conductivity is greatly improved, but also the electrochemical stability and battery characteristics are excellent, so that the lithium polymer secondary battery. It can be used as an all-solid polymer electrolyte for electrochemical devices such as fuel cells.

1 is a graph evaluating the crystallinity according to the temperature change of the all-solid polymer electrolyte prepared in Comparative Example 2 of the present invention with DSC (Differntial Scanning Calorimetry) data.
Figure 2 is a graph evaluating the crystallinity according to the temperature change of the all-solid polymer electrolyte prepared in Comparative Example 3 of the present invention with DSC data.
Figure 3 is a graph evaluating the crystallinity according to the temperature change of the all-solid polymer electrolyte prepared in Example 3 of the present invention with DSC data.
4 is a graph showing changes in ion conductivity according to the temperature of the all-solid polymer electrolytes prepared in Example 3, Comparative Example 2 and Comparative Example 3.
5 is a graph showing rate-rate characteristics at a low temperature of a lithium polymer secondary battery including an all-solid polymer electrolyte prepared in Comparative Example 2 and Comparative Example 3.
6 is a graph showing the rate-limiting properties of the lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Comparative Example 3 at 25°C.
7 is a graph showing rate-limiting properties at 45° C. of a lithium polymer secondary battery including an all-solid polymer electrolyte prepared in Comparative Example 3.
8 is a graph showing a comparison of rate characteristics at 25°C and 45°C of a lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Comparative Example 3.
9 is a graph showing rate-limiting characteristics at 25°C of a lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Example 3.
10 is a graph showing rate-limiting properties at 45°C of a lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Example 3.
11 is a graph showing a comparison of rate characteristics at 25°C and 45°C of a lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Example 3.

Hereinafter, the present invention will be described in detail.

One aspect of the present invention provides a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte represented by Formula 1 below.

[Formula 1]

In Chemical Formula 1,

x represents the average number of moles of propylene oxide and is from 0.01 to 10; And

y represents the average added mole number of ethylene oxide, and is 0.1 to 15.

In this case, x may have different values for each repeating unit, specifically, x may be 0.1 to 5, 0.3 to 3, or 0.4 to 1.

The y may have different values for each repeating unit, specifically, y may be 0.5 to 10, 1 to 7, or 1.5 to 5.

The multi-branched EO-PO plasticizer for all-solid polymer electrolyte represented by Chemical Formula 1 according to the present invention, which is a problem appearing in the plasticizer of the conventional linear EO structure, induces a rigid structure at room temperature due to high crystallinity to suppress ion migration And it solves the point that the ion conductivity is lowered thereby, exhibits the effect of suppressing the crystallinity exhibited by the plasticizer of the conventional linear EO structure and improving the ion conductivity.

Particularly, by introducing the PO structure, the plasticizer significantly suppresses crystallinity exhibited by the plasticizer of the conventional EO structure, thereby improving the lithium ion conduction properties, and in particular, exhibiting an effect of increasing the ion conductivity at low temperatures.

In addition, even if the plasticizer is introduced in the same manner, the flexibility, ionic conductivity, and rate characteristics of the polymer electrolyte show better effects than the plasticizer of the linear EO-PO structure, as it has a multi-branched structure, not a linear structure. It is an effect that appears.

Another aspect of the invention,

1.0-90.0% by weight of a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte represented by Formula 1;

1.0-90.0 wt% of a multi-branched EO-PO crosslinking agent for an all-solid polymer electrolyte represented by the following Chemical Formula 2;

Lithium salt 1.0-50.0 wt%; And

It provides an all-solid polymer electrolyte composition characterized in that it comprises; 0.1-5.0% by weight of a curing initiator.

[Formula 1]

In Chemical Formula 1,

x represents the average number of added moles of propylene oxide, and is from 0.01 to 10; And

y represents the average added mole number of ethylene oxide, and is 0.1 to 15.

In this case, x may have different values for each repeating unit, specifically, x may be 0.1 to 5, 0.3 to 3, or 0.4 to 1.

In this case, y may have different values for each repeating unit, specifically, y may be 0.5 to 10, 1 to 7, and 1.5 to 5, respectively.

[Formula 2]

In Chemical Formula 2,

m represents the average number of added moles of propylene oxide, and is from 0.01 to 10; And

n represents the average added mole number of ethylene oxide, and is 0.1 to 15.

In this case, m may have different values for each repeating unit, specifically, x may be 0.1 to 5, 0.3 to 3, or 0.4 to 1.

In this case, n may have different values for each repeating unit, specifically, y may be 0.5 to 10, 1 to 7, or 1.5 to 5.

In the all-solid polymer electrolyte composition according to the present invention, the plasticizer may be used alone or in combination with a non-aqueous solution-based polar solvent to improve lithium ion dissociation and lithium ion conductivity to help improve ion conductivity. do.

At this time, as the non-aqueous solution-based polar solvent, alkylene carbonate-based, alkyltetrahydrofuran-based, dioxyran-based, lactone-based and acetonitrile-based or the like can be used alone or in combination. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxyran, 4,4-dimethyl-1,3-dioxyran, γ-butyrolactone, acetonitrile, and the like can be used.

Further, the plasticizer may be contained in the total polymer electrolyte composition in the range of 1.0-90.0% by weight, preferably 30.0-80.0% by weight, and more preferably 45.0-75.0% by weight. Normally, the amount of the plasticizer included in the all-solid polymer electrolyte is directly proportional to the ionic conductivity of the all-solid polymer electrolyte, but if the content is less than 1.0% by weight, the effect of improving the ionic conductivity is weak, and it exceeds 90.0% by weight. In the case, there is a problem that it is difficult to apply to battery manufacturing because the mechanical properties are reduced and cannot be made into a thin film. Therefore, when maintaining the content range, it is possible to manufacture a thin film having a thickness of 100 μm or less.

In the all-solid polymer electrolyte composition according to the present invention, by using a multi-branched EO-PO crosslinking agent for the all-solid polymer electrolyte represented by the formula (2), a semi-IPN in which a plasticizer is entangled in a solid network structure generated by the polymerization reaction (Interpenetrating Polymer Network) structure can be formed. The semi IPN structure by the crosslinking agent provides mechanical properties to the polymer electrolyte, and the plasticizer imparts ionic conductivity properties.

In this case, the multi-branched EO-PO crosslinking agent for all-solid polymer electrolyte is contained in the total all-solid polymer electrolyte composition at 1.0-90.0% by weight, preferably 5.0-80.0% by weight, more preferably 8.0-60% by weight. Can. When the content is less than 1.0% by weight, the amount is too small to obtain an effect as a crosslinking agent, and there is a problem that mechanical properties are deteriorated, and when it exceeds 90.0% by weight, there is a problem that the ionic conductivity decreases.

In the all-solid polymer electrolyte composition according to the present invention, the lithium salt is not particularly limited as it is commonly used in all-solid polymer electrolyte production in the art. LiClO ₄ , LiCF ₃ SO ₃ , LiBF ₄ , LiPF ₆ , LiAsF ₆ and LiN(SO ₂ CF ₃ ) ₂ may be used as the lithium salt generally used in the related art.

At this time, the lithium salt may be included in the total polymer electrolyte composition 1.0-50.0% by weight, preferably 10.0-35.0% by weight, more preferably 15.0-30.0% by weight, but the amount by appropriate mixing ratio as necessary You can also adjust If the content is less than 1.0% by weight, the concentration of lithium ions is too low to be suitable as an electrolyte, and when it exceeds 50.0% by weight, there is a problem of solubility of lithium salts and a decrease in ionic conductivity.

In the all-solid polymer electrolyte composition according to the present invention, the curing type initiator may be any initiator, such as a photo-curing type, a heat-curing type, which is generally used in the art.

The photocurable initiator is ethylbenzoin ether, isopropylbenzoin ether, α-methylbenzoin ethyl ether, benzoinphenyl ether, α-acyloxime ester, α,α-diethoxy acetophenone, 1,1-dichloroaceto Phenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one (Darocur 1173 from Ciba Geigy), 1-hydroxycyclohexyl phenyl ketone [Ciba Geiger (Ciba Geigy's Irgacure 184, Darocure 1116, Igacure 907], anthraquinone, 2-ethyl anthraquinone, 2-chloroanthraquinone, thioxanthone, isopropyl thioxanthone, chlorothioxanthone, benzo Phenone, p-chlorobenzophenone, benzyl benzoate, benzoyl benzoate, and Michael Ketone can be used.

In addition, the thermosetting initiator is benzoyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide, a-cumyl peroxyneodecanoate, a-cumyl peroxyneopeptanoate, t-amyl Peroxyneodecanoate, di-(2-ethylhexyl) peroxy-dicarbonate, t-amyl peroxypivalate, t-butyl peroxypivalate, 2,5-dimethyl-2,5 bis(2 -Ethyl-hexanoyl peroxy) hexane, dibenzoyl peroxide, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, 1,1-di-(t- Amylperoxy) cyclohexane, 1,1-di-(t-butylperoxy) 3,3,5-trimethyl cyclohexane, 1,1-di-(t-butylperoxy) cyclohexane, t-butyl peroxy Oxyacetate, t-butyl peroxybenzoate, t-amyl peroxybenzoate, t-butyl peroxybenzoate, ethyl 3,3-di-(t-amylperoxy) butyrate, ethyl 3,3-di- (t-butylperoxy) peroxide-based initiators such as butyrate and dicumyl peroxide, or 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2-methylpropionamidine) di Compounds such as hydrochloride and 4,4'-azobis (4-cyanovaleric acid) can be used. In the present invention, a thermosetting initiator was used, but this is only an example, and is not limited thereto. The type of initiator may be appropriately selected and used according to a curing method.

At this time, the curable initiator is contained in the total all-solid polymer electrolyte composition in the range of 0.1-5.0% by weight, when the content is less than 0.1% by weight, there is a problem that the effect of the initiator can not be obtained, exceeding 5.0% by weight In this case, there is a problem in that the unreacted initiator after curing lowers the performance of the battery.

Meanwhile, the curable initiator may be appropriately adjusted according to the mixing ratio of other components used simultaneously in the all-solid polymer electrolyte composition.

In addition, the present invention provides an all-solid polymer electrolyte comprising the all-solid polymer electrolyte composition.

The all-solid polymer electrolyte can be obtained by curing by applying heat or light to the all-solid polymer electrolyte composition.

The all-solid polymer electrolyte may form a three-dimensional network structure of a semi-IPN (Interpenetrating Polymer Network) type.

The process of preparing an all-solid polymer electrolyte including the all-solid polymer electrolyte composition will be described in more detail as follows, and the present invention is not limited thereto.

First, the plasticizer and lithium salt according to the present invention are placed in a container in an appropriate ratio and stirred with a stirrer to prepare a solution, and then a multi-branched EO-PO crosslinking agent for an all-solid polymer electrolyte according to the present invention is mixed and added to the solution. Then, when an initiator for curing is added and stirred, a mixed solution for preparing an all-solid polymer electrolyte is prepared. The mixed solution is coated on a support such as a glass plate, a polyethylene-based vinyl, or a commercial Mylar film or a battery electrode to an appropriate thickness to induce a curing reaction under irradiation conditions such as electron beams, ultraviolet rays, gamma rays, or heating conditions.

As another manufacturing method for obtaining an electrolyte having a constant thickness, a composition mixture solution is applied on the support, and a spacer for adjusting thickness is fixed at both ends of the support, and then another support is covered thereon, and then the curing irradiator is applied. Alternatively, an all-solid polymer electrolyte is prepared by curing reaction using a heat source.

Another aspect of the present invention provides a lithium polymer secondary battery comprising the all-solid polymer electrolyte composition.

The process of preparing an all-solid polymer electrolyte of a lithium polymer secondary battery, which is another application example of the all-solid polymer electrolyte composition according to the present invention, will be described in more detail as follows and the present invention is not limited thereto.

The lithium polymer secondary battery is composed of a positive electrode, an electrolyte, and a negative electrode. As the positive electrode, lithium metal oxides such as LiFePO ₄ , LiCoO ₂ , and LiNiO ₂ are frequently used. As the negative electrode, carbon series such as graphite or coke such as MCMB, MPCF, etc. Or lithium metal.

The method for manufacturing a lithium polymer secondary battery can be manufactured by any method commonly used in the field to which the present invention pertains, in addition to the method described above.

Another aspect of the present invention provides a fuel cell including the all-solid polymer electrolyte composition.

As described above, the all-solid polymer electrolyte obtained by curing the all-solid polymer electrolyte composition according to the present invention has crystallization suppressed (see FIG. 3 of Experimental Example 1) and improves ion conductivity, even at particularly low temperatures (below 25°C). Because the ionic conductivity is excellent (see Fig. 4 of Experimental Example 2), the discharge capacity of the lithium polymer secondary battery using the above electrolyte is increased (see Figs. 9 and 10 of Experimental Example 3) and the rate characteristics are excellent (experimental) It can be usefully used as an all-solid polymer electrolyte such as FIG. 11) of Example 4, a lithium polymer secondary battery, a fuel cell.

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples and experimental examples are only to specifically illustrate the present invention in one aspect, the present invention is not limited thereto.

< Example 1> All For polymer electrolyte Basin Preparation of EO-PO plasticizer

[Chemical structure of multi-branched EO-PO plasticizer for all-solid polymer electrolyte]

In the above formula,

0.47 is the average added mole number of propylene oxide; And

2.4 is the average added mole number of ethylene oxide.

[Intermediate Compound (A)]

In the above formula,

0.47 is the average added mole number of propylene oxide; And

2.4 is the average added mole number of ethylene oxide.

Trimethylolpropane (134 g, 1 mol) and potassium hydroxide (1.0 g, 17.8 mmol) were added to a high pressure reactor having a thermometer, stirrer, and nitrogen introduction tube, and the inside of the reactor was replaced with nitrogen while stirring. The reactor temperature was set to 140° C., and ethylene oxide (317 g, 7.2 mol) and propylene oxide (82 g, 1.4 mol) were continuously injected for 2 hours while maintaining an internal pressure of 2 to 4 kg/cm ² . The mixture was aged for 3 hours to obtain the intermediate compound (A). Put the intermediate compound (A) (500 g, 0.94 mol) and sodium hydroxide (135 g, 1.35 mol) into a 1L 4-neck glass flask equipped with a thermometer, stirrer, and nitrogen introduction tube and vacuum pump at an internal temperature of 80°C. 1 Time dehydration was performed. After replacing with nitrogen, dimethyl sulfate (426 g, 3.38 mol) was added dropwise at an internal temperature of 50° C. and reacted for 5 hours. It was neutralized with sulfuric acid to pH 5-7, and dehydration was conducted under reduced pressure for 2 hours using a vacuum pump at 100°C to remove moisture contained in the compound. In addition, filtration was performed with diatomaceous earth to remove the salt generated after moisture removal, thereby obtaining a liquid multi-branched EO-PO plasticizer for polymer electrolyte (molecular weight 574 g/mol) (496 g, 0.86 mol). When analyzed by ASTM D4274 (Acetylation) for terminal hydroxyl analysis, the intermediate compound (A) had a hydroxyl value of 316, and the hydroxyl value of the multi-branched EO-PO plasticizer for all-solid polymer electrolyte was 1.8.

< Example 2> All For polymer electrolyte Basin EO-PO Crosslinker Produce

[Chemical structure of multi-branch EO-PO crosslinker for all-solid polymer electrolyte]

In the above formula,

0.47 is the average added mole number of propylene oxide; And

2.4 is the average added mole number of ethylene oxide.

Intermediate compound (A) prepared in Example 1 (400 g, 0.75 mol), acrylic acid (180 g, 2.50 mol), and toluene (360 g, 3.91) as a solvent in a four-neck reactor equipped with a thermometer, stirrer, and reflux tube. mol) is added, stirred at room temperature, methanesulfonic acid (10 g, 0.10 mol), hydroquinone (0.7 g, 6.36 mmol) is added as a catalyst, and the reaction is carried out for 12 hours while the temperature of the reactor is set to 120° C. under oxygen conditions. Proceeded. After the reaction, to remove water and toluene contained in the tablets and compounds, 50 mmHg, 70°C, and distillation under reduced pressure were performed for 8 hours. A multi-branched EO-PO crosslinking agent for solid polymer electrolyte (molecular weight 692 g/mol) (493 g, 0.71 mol) was obtained. When analyzed by ASTM D4274 (Acetylation) for the analysis of the terminal hydroxyl group, the hydroxyl value of the multi-branched EO-PO crosslinking agent for the all-solid polymer electrolyte was found to be 5.3.

< Example 3> Using multi-branch EO-PO plasticizer All Preparation of polymer electrolyte

Plasticizer: Multi-branched EO-PO plasticizer for all-solid polymer electrolyte prepared in Example 1 (0.8 g, 1.394 mmol);

Lithium salt: LiN(SO ₂ CF ₃ ) ₂ (0.206 g, 0.718 mmol);

Crosslinking agent: Multi-branched EO-PO crosslinking agent for all-solid polymer electrolyte prepared in Example 2 (0.8 g, 1.156 mmol); And

Initiator: t -butyl peroxypivalate (2% by weight relative to the total weight of the crosslinker).

The plasticizer and lithium salt were stirred at room temperature until a uniform mixture was obtained. The crosslinking agent and the initiator were added to the mixture and stirred to prepare a precursor solution. The precursor solution was coated on a substrate and cured by applying heat to prepare an all-solid polymer electrolyte in a film form.

< Comparative example 1> All Preparation of linear EO-PO plasticizer for polymer electrolytes

[Chemical structure of linear EO-PO plasticizer for all-solid polymer electrolyte]

In the above formula,

6.3 is the average added mole number of propylene oxide; And

14.5 is the average added mole number of ethylene oxide.

[Intermediate Compound (B)]

In the above formula,

6.3 is the average added mole number of propylene oxide; And

14.5 is the average added mole number of ethylene oxide.

Methanol (32 g, 1 mol) and potassium hydroxide (1.0 g, 17.8 mmol) were added to a high-pressure reactor having a thermometer, stirrer, and nitrogen introduction tube, and the inside of the reactor was replaced with nitrogen while stirring. The reactor temperature was set to 140° C., and ethylene oxide (638 g, 14.5 mol) and propylene oxide (365 g, 6.3 mol) were continuously injected for 5 hours while maintaining an internal pressure of 2 to 4 kg/cm ² . The mixture was aged for 3 hours to obtain the intermediate compound (B). Put the intermediate compound (B) (517.5 g, 0.5 mol) and sodium hydroxide (24 g, 0.24 mol) in a 1L 4-neck glass flask equipped with a thermometer, stirrer, and nitrogen introduction tube and vacuum pump at an internal temperature of 80°C. 1 Time dehydration was performed. After replacing with nitrogen, dimethyl sulfate (75.5 g, 0.6 mol) was added dropwise at an internal temperature of 50° C. and reacted for 5 hours. It was neutralized with sulfuric acid to pH 5-7, and dehydration was conducted under reduced pressure for 2 hours using a vacuum pump at 100°C to remove moisture contained in the compound. After removing the water, filtration was performed with diatomaceous earth to remove the resulting salt, thereby obtaining a linear EO-PO plasticizer (molecular weight 1050 g/mol) (495 g, 0.47 mol) for a liquid all-solid polymer electrolyte. When analyzed by ASTM D4274 (Acetylation) for the analysis of the terminal hydroxyl group, the intermediate compound (B) had a hydroxyl value of 54.2, and the hydroxyl value of the linear EO-PO plasticizer for the all-solid polymer electrolyte was 0.5.

< Comparative example 2> Using PEG plasticizer All Preparation of polymer electrolyte

Plasticizer: poly(ethylene glycol) dimethyl ether (PEGDME, weight average molecular weight (Mw) 1000) (0.8 g, 0.8 mmol);

Lithium salt: LiN(SO ₂ CF ₃ ) ₂ (0.282 g, 0.983 mmol);

Crosslinking agent: Multi-branched EO-PO crosslinking agent for all-solid polymer electrolyte prepared in Example 2 (0.2 g, 0.289 mmol); And

Initiator: t -butyl peroxypivalate (2% by weight relative to the total weight of the crosslinker).

The plasticizer and lithium salt were stirred at room temperature until a uniform mixture was obtained. The crosslinking agent and the initiator were added to the mixture and stirred to prepare a precursor solution. The precursor solution was coated on a substrate and cured by applying heat to prepare an all-solid polymer electrolyte in a film form.

< Comparative example 3> Using linear EO-PO plasticizer All Preparation of polymer electrolyte

Plasticizer: Linear EO-PO plasticizer for all-solid polymer electrolyte prepared in Comparative Example 1 (0.8 g, 0.762 mmol);

Lithium salt: LiN(SO ₂ CF ₃ ) ₂ (0.263 g, 0.918 mmol);

Crosslinking agent: Multi-branched EO-PO crosslinking agent for all-solid polymer electrolyte prepared in Example 2 (0.2 g, 0.289 mmol); And

Initiator: t -butyl peroxypivalate (2% by weight relative to the total weight of the crosslinker).

The plasticizer and lithium salt were stirred at room temperature until a uniform mixture was obtained. The crosslinking agent and the initiator were added to the mixture and stirred to prepare a precursor solution. The precursor solution was coated on a substrate and cured by applying heat to prepare an all-solid polymer electrolyte in a film form.

< Experimental Example 1> All Evaluation of crystallinity according to temperature change of polymer electrolyte

The crystallinity according to the temperature change of all solid polymer electrolytes prepared in Example 3, Comparative Example 2 and Comparative Example 3 was evaluated by DSC (Differential Scanning Calorimetry). In the temperature range of -80°C to 100°C, the change in heat quantity was observed at a heating rate of 10°C/min to measure the temperature at which crystallization and melting of the all-solid polymer electrolyte film occurred.

DSC data of the all-solid polymer electrolyte prepared in Comparative Example 2 is shown in Figure 1,

DSC data of the all-solid polymer electrolyte prepared in Comparative Example 3 is shown in Figure 2,

DSC data of the all-solid polymer electrolyte prepared in Example 3 is shown in FIG. 3.

1 is a graph evaluating the crystallinity according to the temperature change of the all-solid polymer electrolyte prepared in Comparative Example 2 of the present invention with DSC (Differntial Scanning Calorimetry) data.

Figure 2 is a graph evaluating the crystallinity according to the temperature change of the all-solid polymer electrolyte prepared in Comparative Example 3 of the present invention with DSC data.

Figure 3 is a graph evaluating the crystallinity according to the temperature change of the all-solid polymer electrolyte prepared in Example 3 of the present invention with DSC data.

As shown in Figure 1,

In the case of the all-solid polymer electrolyte (Comparative Example 2) containing a linear EO plasticizer (PEGDME), a peak showing crystallization and melting was observed in a temperature range of -80°C to 100°C. In the case of the first temperature increase experiment, crystallization was observed at -25°C, and a melting peak was observed at 19°C. In the case of the second temperature increase experiment, crystallization was observed at -29°C and a melting peak at 25°C. Meanwhile, in the cooling process, crystallization appears at -29°C. According to the observation result of the crystallization peak, crystallization occurred in an all-solid polymer electrolyte containing a linear EO plasticizer.

As shown in Figure 2,

In the case of the all-solid polymer electrolyte (Comparative Example 3) containing a linear EO-PO plasticizer, there is no peak showing crystallization and melting. From these results, in the case of an all-solid polymer electrolyte containing a linear EO-PO plasticizer, crystallization is greatly suppressed to maintain an amorphous state.

As shown in Figure 3,

Even in the case of an all-solid polymer electrolyte (Example 3) containing a multi-branched EO-PO plasticizer, there is no peak showing crystallization and melting. As a result of this, even in the case of an all-solid polymer electrolyte containing a multi-branched EO-PO plasticizer, crystallization is greatly suppressed to maintain an amorphous state. As described above, the introduction of the PO structure and the introduction of the multi-branched structure show excellent effects of greatly suppressing crystallization of the all-solid polymer electrolyte.

< Experimental Example 2> All Evaluation of ion conductivity according to temperature change of polymer electrolyte

In order to confirm the improvement in ion conductivity by suppressing crystallization, the ion conductivity of the all-solid polymer electrolyte was evaluated as follows. Specifically, ionic conductivity according to the temperature change of the all-solid polymer electrolytes prepared in Example 3, Comparative Example 2 and Comparative Example 3 was measured.

The precursor solutions prepared in Example 3, Comparative Example 2 and Comparative Example 3 were respectively injected into a conductive glass substrate, thermally cured, polymerized, cooled sufficiently, and measured by an AC impedance analyzer. The ionic conductivity was evaluated by analyzing the complex impedance by analyzing the obtained measurement with a frequency response analyzer (manufacturer: Zahner Elekrik, model name: IM6).

The changes in the ionic conductivity according to the temperature of the all-solid polymer electrolytes prepared in Example 3, Comparative Example 2 and Comparative Example 3 are shown in FIG. 4.

4 is a graph showing changes in ion conductivity according to the temperature of the all-solid polymer electrolytes prepared in Example 3, Comparative Example 2 and Comparative Example 3.

As shown in Figure 4,

The all-solid polymer electrolyte containing the linear EO plasticizer (PEGDME) (Comparative Example 2) showed ion conductivity similar to that of the all-solid polymer electrolyte (Comparative Example 3) containing the linear EO-PO plasticizer at a temperature of 25° C. or higher. At temperatures below ℃, the ionic conductivity rapidly decreases.

The all-solid polymer electrolyte containing a linear EO-based plasticizer exhibits crystallinity at 25° C. or lower, as shown in FIG. 1, thereby inhibiting the mobility of lithium ions and rapidly decreasing ionic conductivity.

On the other hand, the all-solid polymer electrolyte containing the linear EO-PO plasticizer for all-solid polymer electrolyte (Comparative Example 3) maintains an amorphous state without any crystallinity, so a sharp decrease in ion conductivity due to temperature drop is not seen and is a stable value. This appears.

On the other hand, the all-solid polymer electrolyte containing a multi-branched EO-PO plasticizer (Example 3) also maintains an amorphous state without any crystallinity as the all-solid polymer electrolyte containing a linear EO-PO plasticizer. There is no sudden decrease in ion conductivity.

In particular, the all-solid polymer electrolyte containing a multi-branched EO-PO plasticizer shows a higher ionic conductivity than the all-solid polymer electrolyte containing a linear EO-PO plasticizer regardless of temperature change. As a result of this, the all-solid polymer electrolyte containing a multi-branched EO-PO plasticizer is superior in ionic conductivity to the all-solid polymer electrolyte containing a linear EO-PO plasticizer.

< Experimental Example 3> Battery characteristics evaluation 1

The rate characteristics at a low temperature of the lithium ion battery including the all-solid polymer electrolytes prepared in Comparative Example 2 and Comparative Example 3 are shown in FIG. 5 and specifically, the following experiments were performed.

In order to check the capacity of the lithium ion battery using the all-solid polymer electrolytes prepared in Comparative Examples 2 and 3 as electrolytes and separators and using lithium metal as the negative electrode and LiFePO ₄ as the positive electrode, charge and discharge the tester at 10°C. Discharge behavior was measured. The loading content of the positive electrode active material used was 1.4 mg/cm ² . At this time, the charge upper limit voltage was set to 4.2 V, the discharge lower limit voltage was set to 2.5 V, and the charge/discharge rate was performed at 0.2, 0.5, 1.0, and 2.0 C.

The charge/discharge rate used in this example is expressed in units of "C", and 1 C means a current capable of charging or discharging the discharge capacity of the battery in 1 hour. That is, in the case of a battery having a discharge capacity of 10 Ah, it is referred to as 1 C when charging/discharging with a current of 10 A.

5 is a graph showing rate-rate characteristics at a low temperature of a lithium polymer secondary battery including an all-solid polymer electrolyte prepared in Comparative Example 2 and Comparative Example 3.

As shown in Figure 5,

In the case of a lithium polymer secondary battery using an all-solid polymer electrolyte (Comparative Example 3) containing a linear EO-PO plasticizer, the discharge capacity was about 50 mAh/g at a charge/discharge rate of 0.2 C, whereas a linear EO plasticizer was used. In the case of the lithium polymer secondary battery using the all-solid polymer electrolyte (Comparative Example 2), the discharge capacity was hardly expressed.

The all-solid polymer electrolyte containing a linear EO plasticizer shows crystallization of EO at 10°C, as confirmed in Experimental Example 1, and as confirmed in Experimental Example 2, the ion conductivity is greatly reduced, and the measured ion conductivity is 1.2 ⅹ. It is as low as 10 ^-5 S/cm. As such, since the ionic conductivity is very low, a lithium polymer secondary battery using an all-solid polymer electrolyte containing a linear EO plasticizer rarely exhibits a discharge capacity.

On the other hand, since the all-solid polymer electrolyte containing a linear EO-PO plasticizer shows a higher ionic conductivity than the all-solid polymer electrolyte containing a linear EO-based plasticizer at 10°C, the discharge capacity of the lithium polymer secondary battery increases. As such, the EO-PO polymer electrolyte is superior to the EO polymer electrolyte in battery performance.

< Experimental Example 4> Battery characteristics evaluation 2

An experiment was conducted to compare the battery characteristics of the all-solid polymer electrolyte containing a linear EO-PO plasticizer and the all-solid polymer electrolyte containing a multi-branched EO-PO plasticizer. The following experiment was conducted to compare the rate-limiting characteristics at 25°C and 45°C of the lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Comparative Example 3 and Example 3.

Specifically, in order to confirm the capacity of the lithium ion battery using the all-solid polymer electrolyte prepared in Comparative Examples 3 and 3 as an electrolyte and a separator, and using lithium metal as a negative electrode and LiFePO ₄ as a positive electrode, 25°C and 45°C In the charge and discharge test, the charge and discharge behavior was measured. The loading content of the positive electrode active material used was 5.1 mg/cm ² . At this time, the charge upper limit voltage was set to 4.2 V, the discharge lower limit voltage was set to 2.5 V, and the charge/discharge rate was performed at 0.2, 0.5, 1.0, and 2.0 C.

Figure 6 shows the rate-rate characteristics at 25 ℃ of the lithium polymer secondary battery comprising the all-solid polymer electrolyte prepared in Comparative Example 3.

7 shows the rate-limiting properties of the lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Comparative Example 3 at 45°C.

8 is a comparison of rate characteristics at 25°C and 45°C of a lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Comparative Example 3.

Figure 9 shows the rate-rate characteristics at 25 ℃ of the lithium polymer secondary battery comprising the all-solid polymer electrolyte prepared in Example 3.

10 shows the rate-limiting properties of the lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Example 3 at 45°C.

11 is a comparison of rate characteristics at 25°C and 45°C of a lithium polymer secondary battery including the all-solid polymer electrolyte prepared in Example 3.

As shown in Figure 6,

A lithium polymer secondary battery prepared from an all-solid polymer electrolyte (Comparative Example 3) containing a linear EO-PO plasticizer has a low discharge capacity of 15 mAh/g at 25°C and 0.2 C.

As shown in Figure 9,

A lithium polymer secondary battery prepared from an all-solid polymer electrolyte (Example 3) containing a multi-branched EO-PO plasticizer has a discharge capacity of 142 mAh/g at 25°C and 0.2 C. These results indicate that the multi-branch EO-PO all-solid polymer electrolyte has a better discharge capacity than the linear EO-PO all-solid polymer electrolyte.

7 and 8,

A lithium polymer secondary battery prepared from an all-solid polymer electrolyte (Comparative Example 3) containing a linear EO-PO plasticizer expressed a high capacity of 143 mAh/g at 0.2 C at 45°C, but 18 mAh/at a rate of 0.5 C. It showed a very low dose of g.

10 and 11,

A lithium polymer secondary battery prepared from an all-solid polymer electrolyte containing a multi-branched EO-PO plasticizer (Example 3) expressed a high capacity of 155 mAh/g at 0.2 C at 45°C, and 145 at a rate of 0.5 C. It showed a very high capacity of mAh/g. These results indicate that the multi-branch EO-PO all-solid polymer electrolyte exhibits superior rate characteristics than the linear EO-PO all-solid polymer electrolyte.

Claims (11)

Ethylene oxide (EO)-PO (Ethylene oxide) plasticizer for all-solid polymer electrolyte represented by the following formula (1):
[Formula 1]

(In the formula 1,
x represents the average number of added moles of propylene oxide, and is from 0.01 to 10; And
y represents the average added mole number of ethylene oxide and is 0.1 to 15).
According to claim 1,
X is 0.1 to 5; And
y is a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte, characterized in that 0.5 to 10.
1.0-90.0% by weight of a multi-branched EO-PO plasticizer for an all-solid polymer electrolyte represented by Formula 1;
1.0-90.0 wt% of a multi-branched EO-PO crosslinking agent for an all-solid polymer electrolyte represented by the following Chemical Formula 2;
Lithium salt 1.0-50.0 wt%; And
Curable initiator 0.1-5.0% by weight; all-solid polymer electrolyte composition comprising:
[Formula 1]

(In the formula 1,
x represents the average number of added moles of propylene oxide, and is from 0.01 to 10; And
y represents the average number of moles of ethylene oxide and is 0.1 to 15); And
[Formula 2]

(In the formula 2,
m represents the average number of added moles of propylene oxide, and is from 0.01 to 10; And
n represents the average added mole number of ethylene oxide, and is 0.1 to 15).
According to claim 3,
The lithium salt is an all-solid polymer electrolyte composition, characterized in that at least one member selected from the group consisting of LiClO ₄ , LiCF ₃ SO ₃ , LiBF ₄ , LiPF ₆ , LiAsF ₆ and LiN(SO ₂ CF ₃ ) ₂ .
According to claim 3,
The curable initiator is an all-solid polymer electrolyte composition, characterized in that at least one member selected from the group consisting of a photocurable initiator and a thermosetting initiator.
The method of claim 5,
The photocurable initiator is ethylbenzoin ether, isopropylbenzoin ether, α-methylbenzoin ethyl ether, benzoinphenyl ether, α-acyloxime ester, α,α-diethoxy acetophenone, 1,1-dichloroaceto Phenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, anthraquinone, 2-ethyl anthraquinone, 2-chloroanthraquinone, thioxanthone, isopropyl One or more selected from the group consisting of thioxanthone, chlorothioxanthone, benzophenone, p-chlorobenzophenone, benzylbenzoate, benzoylbenzoate and microkeletone;
The thermosetting initiator is benzoyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide, α-cumyl peroxyneodecanoate, α-cumyl peroxyneopeptanoate, t-amyl peroxy Neodecanoate, di-(2-ethylhexyl) peroxy-dicarbonate, t-amyl peroxypivalate, t-butyl peroxypivalate, 2,5-dimethyl-2,5 bis(2-ethyl -Hexanoyl peroxy) hexane, dibenzoyl peroxide, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, 1,1-di-(t-amylper Oxy) cyclohexane, 1,1-di-(t-butylperoxy) 3,3,5-trimethyl cyclohexane, 1,1-di-(t-butylperoxy) cyclohexane, t-butyl peroxyacetate , t-butyl peroxybenzoate, t-amyl peroxybenzoate, t-butyl peroxybenzoate, ethyl 3,3-di-(t-amylperoxy) butyrate, ethyl 3,3-di-(t -Butylperoxy) butyrate, dicumyl peroxide, 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 4,4'- All-solid polymer electrolyte composition, characterized in that at least one member selected from the group consisting of azobis (4-cyanovaleric acid).
An all-solid polymer electrolyte comprising the all-solid polymer electrolyte composition of claim 3.
The method of claim 7,
The all-solid polymer electrolyte is obtained by curing by applying heat or light to the all-solid polymer electrolyte composition of claim 3.
The method of claim 7,
The all-solid polymer electrolyte is an all-solid polymer electrolyte characterized in that it forms a three-dimensional network structure of a semi-IPN (Interpenetrating Polymer Network) type.
A lithium polymer secondary battery comprising the all-solid polymer electrolyte composition of claim 3.
A fuel cell comprising the solid polymer electrolyte composition of claim 3.

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