KR20170050660A - Solid polymer electrolyte composition and lithium secondary battery including the same - Google Patents

Abstract

The present invention relates to a solid polymer electrolyte composition and a lithium secondary battery comprising the solid polymer electrolyte composition. According to one embodiment of the present invention, a polymer matrix having high molecular weight increases mechanical strength of a solid polymer electrolyte. In addition, the solid polymer electrolyte composition comprises: an organic solvent; a polymer matrix; an additive containing a polyhedral silsesquioxane; and lithium salt.

Description

TECHNICAL FIELD [0001] The present invention relates to a solid polymer electrolyte composition and a lithium secondary battery comprising the polymer electrolyte composition.

The present invention relates to a solid polymer electrolyte composition, and a lithium secondary battery comprising the solid polymer electrolyte composition.

Much research is underway to focus on alternative energy sources and alternate power sources, ie, electrochemical energy production, in order to respond to soaring energy consumption and change to environmentally friendly consumption patterns. BACKGROUND ART [0002] Many researches have been conducted on a lithium secondary battery, which is known to have the best discharge performance at present, including a secondary battery, a fuel cell, and a capacitor, for storing and converting electrochemical energy.

The rechargeable battery is one of the three core strategic products that will lead the domestic electronic information appliance industry along with semiconductors and displays, and it affects the performance of future mobile IT products closely related to the lives of humanity in the 21st century such as mobile phones, notebooks, computers, camcorders, MP3s and PDAs As well as the importance of electric vehicles as a power source.

Among them, lithium polymer batteries are most studied due to their high energy density and discharge voltage, and they are now being commercialized in mobile phones and camcorders.

Of the electrolytes used in lithium polymer batteries, polyethylene oxide (PEO) based polymer electrolytes are known as one of the most promising polymer electrolytes. However, the polymer electrolyte using PEO has a relatively high ionic conductivity of 10 ^-4 S / cm at a high temperature of 60 ° C or higher, but the ionic conductivity is lowered to 10 ^-8 S / cm at room temperature. This problem is caused by the high crystallinity (χ = ~ 80%) at room temperature of PEO. The movement of ions in the electrolyte is caused by the segmental motion of the polymer and such movement is limited in the crystalline region. Therefore, studies have been made to develop a polymer electrolyte having a high ionic conductivity and mechanical strength at a relatively low temperature and room temperature by suppressing the crystallinity of the polymer electrolyte.

Conventional solid polymer electrolytes for lithium secondary batteries have various additives for the purpose of controlling the crystallinity of PEO, which is a polymer matrix, in order to secure ionic conductivity at room temperature. For example, Korean Patent Registration No. 10-0722834 discloses "a method for producing a polymer electrolyte composite material and a lithium polymer battery comprising the solid polymer electrolyte composite material produced therefrom ". However, in most cases, the crystallinity is controlled when the additive is introduced, but at the same time, the mechanical properties are deteriorated. In addition to the above problems, since the size of the additives itself affects the chain mobility of the PEO chain, it causes an increase in the glass transition temperature (T _g ), which is a very important factor in ion conduction at normal temperature and low temperature It has disadvantages. In addition, when an additive is introduced to improve the strength of the solid polymer electrolyte, the strength of the solid polymer electrolyte is improved but the elongation is also lowered. Therefore, it is necessary to develop an additive capable of simultaneously improving the strength and elongation of the solid polymer electrolyte.

The present invention provides a solid polymer electrolyte composition comprising an organic solvent, a polymer matrix, an additive containing a polyhedral silsesquioxane, and a lithium salt, and a lithium secondary battery comprising the same.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

A first aspect of the present invention relates to a process for the preparation of a compound of formula A polymer matrix containing polyethylene oxide (PEO) having a molecular weight of more than 1,000,000; And an additive containing polyhedral silsesquioxane represented by the following general formula (1): < EMI ID = 1.0 >

[Chemical Formula 1]

;

;

Wherein R ₁ to R ₃ are each independently CH ₂ CH ₂ (OCH ₂ CH ₂ ) _m OCH ₃ and m is 3 to 14;

The second aspect of the present invention provides a lithium secondary battery comprising the solid polymer electrolyte composition according to the first aspect of the present invention, a cathode, and an anode.

According to one embodiment of the present invention, by introducing a nanocomposite additive containing a polyhedral silsesquioxane having a lithium salt and a cage structure, the mechanical strength of the solid polymer electrolyte can be increased by using a high molecular weight polymer matrix, The solid polymer electrolyte according to one embodiment of the present invention can provide a solid polymer electrolyte having improved ionic conductivity by controlling the crystallinity while maintaining the stability of the liquid electrolyte and the gel polymer electrolyte used in conventional lithium ion batteries I can solve the problem.

In addition, since the solid polymer electrolyte of the present invention has a strong mechanical strength, the performance can be maintained even if the thickness is reduced. As a result, the thickness and cost of the lithium secondary battery can be reduced.

In addition, since the solid polymer electrolyte of the present invention has high ionic conductivity, strength and elongation at room temperature, it can contribute to the commercialization of a high capacity lithium polymer secondary battery with ensured stability in the future.

According to one embodiment of the present invention, a polyethylene glycol-polyhedral oligomeric silsesquioxane (PEG-POSS) having a cage structure having an 8-directional polyethylene glycol (PEG) functional group is dissolved in a polymer matrix, Polyoctahedral silsesquioxand-phenyl ₇ (BF ₃ Li) ₃ (POSS Li Salt), a solid polymer electrolyte for a secondary battery having improved ionic conductivity can be produced.

According to one embodiment of the present invention, in order to improve the ionic conductivity of the solid polymer electrolyte for a lithium secondary battery, the amorphous region of the polymer matrix in which ion conduction occurs should be increased. For this purpose, introduction of an additive inhibits the intermolecular interaction of the polymer matrix and lowers the high crystallinity. In the conventional studies, the ionic conductivity can be expected to be improved as the additive is introduced, I was holding it. The solid polymer electrolyte according to one embodiment of the present invention can improve the mechanical strength by increasing the molecular weight of PEO itself as a polymer matrix and improve the mechanical strength of POSS-benzyl ₇ (BF ₃ Li) ₃ salt having a Si- By introducing POSS-PEG having a sesquioxane cage structure as an additive at the center, the mechanical strength is maintained high, and at the same time, the crystallinity is controlled and the ion conductivity is greatly improved.

According to one embodiment of the present disclosure, the POSS-PEG comprises an 8-way PEG functional group. The polyethylene glycol introduced as an additive reduces the crystallinity of the polymer matrix, PEO, due to the plasticizing effect of POSS-PEG, and the ability of the PEG, which is a functional group in eight directions, to dissociate salts on the electrolyte like PEO The ionic conductivity of the solid polymer electrolyte can be improved by increasing the movement of the ions.

According to one embodiment of the present invention, the ionic conductivity and thermal, mechanical, and electrical stability of the solid polymer electrolyte can be improved by adjusting the content of POSS-PEG (7.64 x 10 ^-4 S / cm at 23 ° C) .

1 is a graph showing a differential scanning calorimeter (DSC) analysis result of a solid polymer electrolyte according to an embodiment of the present invention.
2 is a graph showing the ionic conductivity of a solid polymer electrolyte at room temperature in one embodiment of the present invention.
3 is a graph showing the ionic conductivity of a solid polymer electrolyte at room temperature in one embodiment of the present invention.
FIG. 4 is a graph showing conductivity values measured by controlling the EO / Li ratio of the solid polymer electrolyte composition in one embodiment of the present invention. FIG.
5 is a graph showing conductivity values measured by adjusting the content of POSS-PEG in the solid polymer electrolyte composition in one embodiment of the present invention.
6 (a) and 6 (b) are graphs showing the relationship between the solid polymer electrolyte (a) using PEO having a molecular weight value of 1,000,000 and the solid polymer electrolyte (b) using PEO having a molecular weight value of 4,000,000 ).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and examples and drawings.

A first aspect of the present invention relates to a process for the preparation of a compound of formula A polymer matrix containing polyethylene oxide (PEO) having a molecular weight of more than 1,000,000; And an additive containing a polyhedral silsesquioxane represented by the following general formula (1); And a lithium salt, wherein the solid polymer electrolyte composition comprises:

 [Chemical Formula 1]

;

;

Wherein R ₁ to R ₃ are each independently CH ₂ CH ₂ (OCH ₂ CH ₂ ) _m OCH ₃ and m is 3 to 14;

For example, the polyhedral silsesquioxane may include, but is not limited to, a polyhedral oligomeric silsesquioxane (POSS) having a cage structure.

In one embodiment of the present invention, the solid electrolyte composition may include, but is not limited to, a film form or a film form.

Ion conduction of the polymer electrolyte composition occurs in the amorphous region of the polymer contained in the polymer matrix. Therefore, in order to increase the ionic conductivity of the polymer electrolyte composition, intermolecular interaction of the crystalline polymer should be inhibited and the crystallinity thereof should be lowered, and an additive may be introduced for this purpose. However, in the system in which the conventional additives are introduced, crystallinity of the polymer is controlled by the introduction of the additive, which leads to an increase in ionic conductivity, but at the same time, a significant decrease in mechanical properties is caused. In order to alleviate these disadvantages, when cage-structured polyhedral silsesquioxane is incorporated as an additive, which improves the physical properties of the electrolyte through a central silsesquioxane cage structure, the ionic conductivity is improved by controlling the crystallinity, Thereby completing the complementary solid polymer electrolyte. Particularly, when the polymer electrolyte comprising the polyhedral silsesquioxane-containing polymer electrolyte composition of the present invention is used, strength and elongation can be improved at the same time as in the case of using conventional additives.

For example, the polyhedral silsesquioxane may include PEG-polyhedral oligomeric silsesquioxane (PEG-POSS) containing polyethylene glycol (PEG) as a functional group, But may not be limited thereto.

In the case of the polyhedral silsesquioxane represented by Formula 1, the functional groups are connected to eight silicon atoms located in eight directions based on the central cage structure. Eight functional groups each include polyethylene glycol, which is widely used as a plasticizer in the electrolyte system, so that the crystallinity of the solid polymer matrix can be controlled as an additive while complementing the deficient salt dissociation ability of the polymer matrix, have. For example, the polyhedral silsesquioxane is a nano-sized additive. As the amount of the additive increases, the glass transition temperature is lowered and the molecular movement becomes active. At the same time, due to the stable cage structure at the center, Mechanical strength that can be achieved, but may not be limited thereto.

For example, each of the eight functional groups located in eight directions of the polyhedral silsesquioxane represented by Formula 1 may be independently controlled in length, but may not be limited thereto.

In one embodiment of the present invention, the average number m of ethylene oxide (EO) repeating units contained in R ₁ to R ₈ in the general formula (1) ranges from 3 to 14, for example, 14, 3 to 10, 3 to 8, or 3 to 6, 4 to 13, m is 4 to 13, 4 to 10, 4 to 8, or 4 But it may not be limited thereto.

In one embodiment of the present invention, when the m value is reduced, a high conductivity value can be obtained because the crystallinity is reduced due to each EO chain. On the other hand, if the m value is reduced to 3 or less, mobility is increased The Tg becomes very low. Therefore, it is difficult to make film.

For example, the solid polymer electrolyte composition of the present invention may be used in an electrolyte of a lithium secondary battery or a fuel cell, but may not be limited thereto.

When the solid polymer electrolyte composition of the present invention is used in a lithium secondary battery, the EO contained in the polyethylene glycol forms a complex through coordination bond with the lithium salt in the electrolyte to perform ion conduction, Means that more ion conduction sites are provided, and at the same time, the dissociation of the lithium salt is increased, so that more lithium free ions can be transferred. In addition, the presence of the EO repeating unit of polyethylene glycol having a low glass transition temperature lowers the glass transition temperature of the polymer electrolyte, resulting in an increase in the activity of the polymer. For example, the polyethylene glycol may cause an increase in the ion conductivity of the polymer electrolyte due to the above effects, but the present invention is not limited thereto.

For example, the performance of the polymer may be controlled by controlling the number of EO repeating units contained in R ₁ to R ₈ in the above formula (1), but the present invention is not limited thereto. If the average number of the ethylene oxide repeating units contained in R ₁ to R ₈ in the above formula (1) is too large, for example, more than 44, mixing of the polymer matrix and the additive may not be performed well. But may not be limited. Accordingly, by controlling the number of ethylene oxide repeating units included in R ₁ to R ₈ in the formula (1), the length of side branches of the polyhedral silsesquioxane can be controlled, thereby controlling the performance of the solid polymer electrolyte composition of the present invention .

In one embodiment of the present invention, the content of the polyhedral silsesquioxane may be 5 wt% to 50 wt% based on the total weight of the polymer electrolyte composition, but may not be limited thereto. For example, the content of the polyhedral silsesquioxane may be in the range of 5 wt% to 50 wt%, 10 wt% to 50 wt%, 15 wt% to 50 wt%, and 20 wt%, based on the total weight of the polymer electrolyte composition But may not be limited to, 50 wt% to 50 wt%, 5 wt% to 40 wt%, 10 wt% to 40 wt%, 15 wt% to 40 wt%, or 20 wt% to 40 wt%. For example, as the content of the polyhedral silsesquioxane increases, the conductivity increases as the crystallinity decreases. However, since the film formation is difficult due to the reduction of Tg above 50 wt, the optimum effect is obtained at 20-40 wt.

For example, as the amount of polyhedral silsesquioxane introduced into the additive increases, the glass transition temperature (T _g ) of the polymer contained in the polymer matrix may be lower than the T _g of the electrolyte composed solely of polymer and lithium salt , But is not limited thereto. The additive introduced into the conventional solid polymer electrolyte system has an effect on the crystallinity control due to its size, but it has a problem that the glass transition temperature is increased due to decrease of the mobility of the polymer chain. However, polyhedral silsesquioxane, an additive, is a nano-sized additive that lowers the glass transition temperature, which causes molecular motion at low temperatures and at room temperatures. As a result, ionic conductivity at room temperature is lower than that of a polymer matrix and a lithium salt- Improvement can be brought about.

In one embodiment herein, the molecular weight of the polyethylene oxide (PEO) is greater than about 1,000,000, for example, greater than about 1,000,000 to about 10,000,000, greater than about 1,000,000 to about 9,000,000, greater than about 1,000,000 to about From greater than about 1,000,000 to about 3,000,000, or from greater than about 1,000,000 to about 2,000,000, with the proviso that at least about 8,000,000, from about 1,000,000 to about 7,000,000, from about 1,000,000 to about 6,000,000, from about 1,000,000 to about 5,000,000, from about 1,000,000 to about 4,000,000, But may not be limited. For example, when the molecular weight of the polyethylene oxide is about 1,000,000 or less, the glass transition temperature is too low to form a film.

According to one embodiment of the present invention, the organic solvent may be selected from the group consisting of carbonates, esters, ethers, ketones, nitriles, and combinations thereof, but may not be limited thereto.

According to one embodiment of the present invention, the solid polymer electrolyte composition may further include a lithium salt, but the present invention is not limited thereto.

In one embodiment of the present application, polyoctahedral silsesquioxane as described below is the lithium salt _{- phenyl 7 (BF 3 Li)} 3, phytic (BF 3) Li, POSS SA (BF 3) Li Salt, tetrasilanol phenyl POSS (BF 3) _{Li, POSS-benzyl 7 (BF} 3 Li) 3 salt But are not limited to, those selected from the group consisting of combinations thereof, and the like.

For example, the polyhedral silsesquioxane, which is an additive that can be introduced into a solid polymer electrolyte composition including a polymer matrix and a lithium salt, may include a polyethylene glycol (PEG) functional group located in one to eight directions, But may not be limited. When polyethylene glycol is introduced as a plasticizer into a gel-type polymer electrolyte together with polyethylene oxide and a lithium salt, it exhibits a high conductivity of 1 x 10 ^-3 S / cm. Therefore, the polyhedral silsesquioxane is added to the polymer matrix to decrease the crystallinity of the polymer matrix, and at the same time, the polyethylene glycol, which is a functional group in up to eight directions, can dissolve the salt as well as the polymer matrix, such as polyethylene oxide, It is possible to compensate for the insufficient lithium salt dissociation ability of the polymer matrix. The increase in salt dissociation means that the density of dissociated lithium free ions in the electrolyte is increased, and consequently, the ion conductivity of the solid polymer electrolyte is improved.

According to an embodiment of the present invention, the polymer matrix may include, but not limited to, polyethylene oxide (PEO).

In one embodiment of the present invention, the molar ratio of ethylene oxide (EO) contained in the solid polymer electrolyte composition to lithium (Li) contained in the lithium salt may be 4: 1 to 60: 1, .

The second aspect of the present invention provides a lithium secondary battery comprising the solid polymer electrolyte composition according to the first aspect of the present invention, a cathode, and an anode. Although the description of the lithium secondary battery according to the second aspect of the present invention is omitted from the description of the first aspect of the present invention, the description of the first aspect of the present invention is not limited to the second aspect of the present invention As shown in FIG.

For example, the lithium secondary battery may include a high-capacity lithium polymer secondary battery having enhanced stability, and the lithium polymer secondary battery may be thinned and reduced in cost, but the present invention is not limited thereto.

In one embodiment of the invention, the cathode is _{LiMn 2 O 4, LiNi 2 O} 4, LiTi 2 O 4, LiTiS 2, LiCoO 2, LiNiO 2, LiMnO 2, Li 2 MnO 3, LiFePO 4, LiFePO 4, _{LiFePO 4 F, LiMnPO 4, LiCoPO} 4, LiNiPO 4, and may be, but comprising a compound selected from the group consisting of the combinations thereof, may not be limited to:

In one embodiment of the present application, the anode comprises at least one of graphite, graphene, low temperature calcined carbon, calcined coke, vanadium oxide, lithium vanadium oxide, lithium germanium oxide, lithium titanate oxide, , Lithium suicide, and combinations thereof, but may not be limited thereto.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are given to aid understanding of the present invention, and the present invention is not limited to the following examples.

[ Example ]

Example  1. Polyhedron Silsesquioxane  Manufacture of added polymer electrolyte (molecular weight of polyethylene oxide approx. 4,000,000).

In this embodiment, a solid polymer electrolyte to which polyhedral glycol silsesquioxane was added was prepared. The reagents required for the preparation were purchased from Aldrich and Hybrid Plastic. POSS-benzyl ₇ (BF ₃ Li) ₃ (hybrid Plastics) was used as a solvent and polyethylene oxide (PEO, Aldrich) having a molecular weight of about 4,000,000 and acetonitrile (99.8%, Aldrich) . In addition, solid polyelectrolytes in the form of thin films were prepared by using polyhedral silsesquioxanes as an additive.

Polyhedral silsesquioxane as an additive was added to the polymer matrix PEO as 5 wt%, 10 wt%, 20 wt%, and 50 wt% of the total weight. Next, the amount of POSS Li Salt, which is a lithium salt, was added at a ratio of [EO] / [Li] of 14/1 in order to form a PEO-lithium salt complex, and they were dissolved in acetonitrile as an organic solvent. For complete dissociation of the lithium salt and formation of a stable complex with PEO and even dispersion of the polyhedral silsesquioxane, the solution is stirred sufficiently (max. 24 hours) in a 50 ° C oil bath using a magnetic bar to obtain a homogeneous solution made. At this time, ultrasonic treatment was performed in the middle, so that polyhedral silsesquioxane as an additive could be dispersed evenly and uniformly without aggregation. The homogeneous solution obtained by this process was placed in teflon petridish and solution casting was used to form an electrolyte membrane. Then, in order to completely block the contact with moisture at room temperature, the electrolyte membrane was dried in a glove box under high purity nitrogen for 4 days to 5 days, and the polyelectrolyte containing polyhedral silsesquioxane was removed by sufficiently removing acetonitrile as a solvent. .

Example  2. Polyhedron Silsesquioxane  Addition of Polymer Electrolyte Preparation (Polyethylene Oxide  Molecular weight about 8,000,000)

A polyelectrolyte containing polyhedral silsesquioxane was prepared using the same method as described in Example 1, except that polyethylene oxide having a molecular weight of about 8,000,000 was used. At this time, the POSS-PEG was prepared as follows.

First, monomethyl-PEG and excess allyl bromide were added, refluxed at 50 ° C for 24 hours in the presence of NaOH, and vacuum filtered to remove residual allyl Allyl-PEO (allyl-PEO) was synthesized by drying in a vacuum oven at 60 ° C for 24 hours to remove the bromide. The process for preparing the allyl-PEO is shown in Scheme 1 below:

[Reaction Scheme 1]

Next, octasilane-POSS and excess allyl-PEO were added together and the moisture was removed at 60 DEG C for 24 hours in a vacuum, followed by heating at 110 DEG C for 24 hours. Then, pure CH ₂ Cl ₂ was dissolved in nitrogen atmosphere, Karstedt's catalyst was slowly dropped by one drop, and the mixture was refluxed at 40 ° C for 48 hours, mixed with activated carbon, and vacuum filtered POSS-PEG was prepared. The remaining solvent was evaporated under reduced pressure. The preparation of POSS-PEG is shown in Scheme 2 below:

[Reaction Scheme 2]

Example  3. Measurement of Glass Transition Temperature and Crystallinity of Polymer Electrolyte (Polyethylene Oxide  Molecular weight about 4,000,000)

In this embodiment, polyhedral silsesquioxane is added to the total amount of 0 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt% of PEO having a molecular weight of about 4,000,000 and lithium salt (POSS Li Salt) %, And 60 wt% of solid polymer electrolyte and pure PEO were measured. FIG. 1 is a graph showing the results of analysis of the solid polymer electrolytes by differential scanning calorimetry (DSC), and Table 1 is a numerical representation of the results of FIG. The results shown in FIG. 1 and Table 1 show that as the amount of the polyhedral silsesquioxane introduced as the additive increases, the crystallinity of the PEO decreases, and the melting temperature and the peak area in the melt section decrease.

[Table 1]

Example  4. Measurement of Glass Transition Temperature and Crystallinity of Polymer Electrolyte (Polyethylene Oxide  Molecular weight about 8,000,000)

In this embodiment, PEO having a molecular weight of about 8,000,000 and POSS Li Salt ([EO]: [Li] = 14: 1) were used to obtain a polyhedral siloxane having an average number of PEO residues of about 4, Oxime [POSS-PEG ₄ ] were added to 0 wt%, 10 wt%, and 40 wt% of the polymer electrolyte, and their glass transition temperatures were compared and measured. The measured glass transition temperatures are shown in Table 2 below.

[Table 2]

Example  5. Polyhedron Silsesquioxane  Solid polymer according to content Ionic conductivity of electrolyte  Change measurement (polyethylene Oxide  Molecular weight about 4,000,000)

In this embodiment, the ionic conductivity of PEO having a molecular weight of about 4,000,000 and a solid polymer electrolyte to which polyhedral silsesquioxane [POSS-PEG ₄ ] was added to a lithium salt (POSS Li Salt) was measured at room temperature. The following Table 3 shows the results of the evaluation of the lithium salt (POSS Li Salt) in which 0 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt% and 60 wt% polyhedral silsesquioxane And the measurement of the ionic conductivity at room temperature of the added solid polymer electrolyte is shown numerically. The ionic conductivity of the solid polymer electrolyte at room temperature was measured by the AC impedance method using an AC impedance analyzer (Solatron Frequency Response Analyzer: 1252A coupled with SI 1287 Electrochemical Interface). A stainless steel electrode was used to measure the ionic conductivity. The sample was taken as a circle having a diameter of 1 cm, inserted between the electrodes inside the cell, and then measured in a wide frequency band. After obtaining the bulk resistance of the electrolyte from the measured AC impedance spectrum (Cole-Cole plot), the ion conductivity was calculated using the following equation:

R =? L / A,? = RA / L, and s = 1 /?

In the above formula, ρ, R, A, L, and s are respectively the resistivity, the measured resistance, the cross-sectional area of the sample, the interelectrode distance, and the ion conductivity.

[Table 3]

According to the above Table 3, in the case of the polyelectrolyte containing no polyhedral silsesquioxane, the ionic conductivity is 8.2 x 10 ^-7 S / cm, whereas in the case of the polyelectrolyte containing polyhedral silsesquioxane, As the amount of sesquioxane increased, ionic conductivity increased and ionic conductivity increased to 4.0 × 10 ^-6 S / cm when 50 wt% polyhedral silsesquioxane was added.

Example  6. Polyhedron Silsesquioxane  Solid polymer according to content Ionic conductivity of electrolyte  Change measurement (polyethylene Oxide  Molecular weight about 8,000,000)

In this embodiment, the ionic conductivity at room temperature of a solid polymer electrolyte in which polyhedral silsesquioxane [POSS-PEG (13)] is added to PEO having a molecular weight of about 8,000,000 and a lithium salt (LiPF ₆ , LiTFSI or LiODFB) Respectively. Table 4 below shows the ionic conductivity at room temperature of a solid polymer electrolyte in which 0 wt%, 5 wt%, 10 wt%, 20 wt%, and / or 50 wt% polyhedral silsesquioxane is added to the lithium salt And the measured values are expressed numerically.

[Table 4]

Table 4 shows that as the content of polyhedral silsesquioxane (POSS-PEG) increases, the ionic conductivity increases and other types of salts such as polyoctahedral silsesquioxane-phenyl ₇ (BF ₃ Li) ₃ , phytic (BF ₃ ) (BF ₃ ) Li salt, tetrasilanol phenyl POSS (BF ₃ ) Li and POSS-benzyl ₇ (BF ₃ Li) ₃ salt].

Example  7. Lithium salt  Polymers according to type Ionic conductivity of electrolyte  Change measurement (polyethylene Oxide  Molecular weight about 1,000,000)

In this example, the ionic conductivity of PEO and polyhedral silsesquioxane having a molecular weight of about 4,000,000 and a solid polymer electrolyte including LiTFSI, LiClO ₄ , or LiPF ₆ as a lithium salt was measured at room temperature. FIG. 2 shows a cross-sectional view of a LiTFSI, LiPF ₆ , or LiClO ₄ Are graphs of the ionic conductivities at room temperature of the polymer electrolyte, respectively. 2, when LiTFSI was used instead of LiPF ₆ , the ionic conductivity at room temperature was 4.3 x 10 ^-5 S / cm at the maximum.

Example  8. Lithium salt  Polymers according to type Ionic conductivity of electrolyte  Change measurement (polyethylene Oxide  Molecular weight about 8,000,000)

In this embodiment, the ion conductivity at room temperature of the solid polymer electrolyte was measured for a molecular weight of about 8,000,000 including the PEO and POSS-PEG (13), and LiTFSI as a lithium salt, LiODFB, or LiPF _6. FIG. 3 shows a cross-sectional view of LiTFSI, LiODFB, or LiPF ₆ Are graphs of the ionic conductivity at room temperature of the solid polymer electrolyte, respectively. As shown in FIG. 3, as the wt% of POSS-PEG POSS increases, the ionic conductivity of the polymer electrolyte containing different lithium salts increases.

Example  9. Measurement of Mechanical Strength of Polymer Electrolyte (Polyethylene Oxide  Molecular weight about 4,000,000)

10 wt%, 20 wt%, and 30 wt%, based on the total weight, of PEO having a molecular weight of about 4,000,000 and polyhedral silsesquioxane POSS-PEG _{4 to a} lithium salt (POSS Li Salt) The tensile test was performed using a universal testing machine (UTM) to confirm the mechanical strength of the solid polymer electrolyte added as 40 wt%, 50 wt%, and 60 wt%. For the test, specimens were prepared in accordance with the American Society for Testing and Materials (ASTM) standard. The specimens were subjected to tensile strain and tensile stress using the strain or fracture caused by the force, Were measured. The resulting yield stress, yield stress, which is the critical stress at the yield point at which elastic deformation occurs, and the yield elongation yield strain, which is the strain, are shown numerically in Table 5 according to the kind of the solid polymer electrolyte. As shown in the following Table 5, the polyelectrolyte containing polyhedral silsesquioxane has a yield stress of at least 1.6 times or more than the polyelectrolyte having no polyhedral silsesquioxane introduced therein as a result of complementing physical properties of the cage structure 2.8 times, and at the same time, the yield stain is increased by 2 to 3 times.

[Table 5]

Example  10. Measurement of Mechanical Strength of Polymer Electrolyte (Polyethylene Oxide  Molecular weight about 8,000,000)

In this example, the mechanical strength of a solid polymer electrolyte in which 0 wt%, 5 wt%, 20 wt%, and 50 wt% of POSS-PEG 13) was added to the total weight of PEO with a molecular weight of about 8,000,000 and lithium salt (LiPF ₆ ) , And the yield strength and yield elongation of the measured solid polymer electrolyte are shown in Table 6 below.

[Table 6]

Referring to Tables 5 and 6, it can be seen that the yield strength and yield elongation of the solid polymer electrolyte containing POSS-PEG were increased compared to those without POSS-PEG (0 wt%).

Example  11. EO / Li  Comparison of Conductivity of Solid Polymer Electrolytes by Ratio

In order to confirm the conductivity value of the solid polymer electrolyte according to the ratio of EO / Li contained in the prepared solid polymer electrolyte, in the system of PEO / POSS (BF ₃ Li) salt, the molecular weight of PEO in the polymer electrolyte composition was fixed at 4,000,000 The conductivity values were measured by varying the EO / Li ratio. As shown in FIG. 4, when the EO / Li ratio was between 12 and 16, the conductivity of the polymer electrolyte was high, and when the EO / Li ratio was 14, the highest value of 1.34 x 10 ^-4 S / cm Respectively.

Example  12. POSS Comparison of Conductivity of Solid Polymer Electrolyte According to PEG Content

(PEO / POSS (BF ₃ Li) salt, EO / Li = 14] and the example [PEO / POSS (BF ₃ Li) salt) to confirm the conductivity value of the solid polymer electrolyte according to the content of POSS- / POSS-PEG ₄ , EO / Li = 14], the molecular weight of the polymer matrix in the solid polymer electrolyte composition was fixed at 4,000,000 and the conductivity value was measured by varying the content of POSS-PEG. As shown in Table 7 and FIG. 5, it can be seen that the conductivity value of the solid polymer electrolyte increases as the content of POSS-PEG increases. Conductivity of the solid polymer electrolyte using PEO / POSS (BF ₃ Li) salt was 1.34 x 10 ^-4 S / cm, but the conductivity of the polymer electrolyte composition using POSS-PEG was increased to 60 wt 1.59 x 10 ^-3 S / cm.

[Table 7]

Example  13. PEO  Comparison of Possibility of Preparing Solid Polymer Electrolytes by Molecular Weight

In order to compare the solid polymer electrolytes according to the molecular weight of the polymer matrix, solid polymer electrolytes were prepared using PEO having a molecular weight of 1,000,000 and PEO having a molecular weight of 4,000,000 in a solid polymer electrolyte composition. As shown in FIG. 6, in the polymer electrolyte using PEO having a molecular weight of 1,000,000, no film was formed, whereas in the polymer electrolyte using PEO having a molecular weight of 4,000,000, a film was formed.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (9)

Organic solvent;
A polymer matrix containing polyethylene oxide (PEO) having a molecular weight of more than 1,000,000;
An additive containing a polyhedral silsesquioxane represented by the following formula (1); And
A solid polymer electrolyte composition comprising a lithium salt:
[Chemical Formula 1]

;
In Formula 1,
R ₁ to R ₃ are each independently CH ₂ CH ₂ (OCH ₂ CH ₂ ) _m OCH ₃ and m is 3 to 14.
The method according to claim 1,
Wherein the average number of ethylene oxide repeating units contained in R ₁ to R ₈ in the general formula (1) is 3 to 6.
The method according to claim 1,
Wherein the polyhedral silsesquioxane content is 5 wt% to 50 wt% based on the total weight of the solid polymer electrolyte composition.
The method according to claim 1,
Wherein the organic solvent is selected from the group consisting of carbonates, esters, ethers, ketones, nitriles, and combinations thereof.
The method according to claim 1,
The lithium salt _{polyoctahedral silsesquioxane - phenyl 7 (BF 3} Li) 3, phytic (BF 3) Li, tetrasilanol phenyl POSS (BF 3) Li, POSS SA (BF 3) Li Salt, POSS-benzyl 7 (BF 3 Li) _Trisodium salt And combinations thereof. ≪ Desc / Clms Page number 18 >
The method according to claim 1,
Wherein the molar ratio of the ethylene oxide (EO) contained in the solid polymer electrolyte composition to lithium (Li) contained in the lithium salt is 4: 1 to 60: 1.
A lithium secondary battery comprising the solid polymer electrolyte composition according to any one of claims 1 to 6, a cathode, and an anode.
8. The method of claim 7,
The cathode may be made of LiMn ₂ O ₄ , LiNi ₂ O ₄ , LiTi ₂ O ₄ , LiTiS ₂ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , Li ₂ MnO ₃ , LiFePO _{4 ,} LiFePO ₄ , LiFePO ₄ F, LiMnPO ₄ , LiCoPO ₄ , LiNiPO ₄ , and combinations thereof.
8. The method of claim 7,
The anode may be selected from the group consisting of graphite, graphene, low temperature calcined carbon, calcined coke, vanadium oxide, lithium vanadium oxide, lithium germanium oxide, lithium titanate oxide, silicon, silica, lithium suicide, A lithium secondary battery, and a lithium secondary battery.

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