KR101915558B1 - Composite electrolyte for secondary battery and method of preparing thereof - Google Patents

Abstract

Provided is a method for producing a composite electrolyte for secondary batteries, comprising the following steps: a first step for acquiring solid electrolyte powder represented by chemical formula 1, Li_ (1 + x) Al_xM_ (2-x) (PO_4) _3; a second step of acquiring a molded composite electrolyte for secondary batteries by mixing the acquired solid electrolyte powder with a polymer electrolyte; and a third step of producing the composite electrolyte for secondary batteries by thermosetting the molded composite electrolyte and applying pressure to the same. In the chemical formula 1, M refers to Ti or Ge, and x satisfies 0 < x < 2. According to the present invention, the composite electrolyte for lithium secondary batteries contains the solid electrolyte and the polymer electrolyte. By containing the polymer electrolyte in the production method, the composite electrolyte can be produced without undergoing a high temperature sintering process which is essential in conventional solid electrolyte production processes, and it is possible to secure excellent mechanical strength and chemical resistance in the solid electrolyte owing to higher content of solid electrolytes compared to the polymer electrolyte.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite electrolyte for a secondary battery,

The present invention relates to a composite electrolyte for a secondary battery, a method for producing the composite electrolyte, and a secondary battery comprising the composite electrolyte.

Lithium secondary batteries are energy sources that convert chemical energy into electrical energy and are attracting attention as energy sources for mobile phones, notebooks, and wearable appliances. However, in order to realize various lithium-ion batteries such as a high-capacity power source device, an extreme temperature driving environment, and a wearable device, which are free from deformation, conventional liquid electrolytes are unsuitable because of safety problems. Recently, various solid state electrolytes such as a polymer electrolyte or a solid electrolyte have been studied as an electrolyte of a lithium ion battery.

Various types of solid electrolytes are generally safe from external impacts and can be processed into various shapes. However, in the case of a ceramic solid electrolyte, practical use due to low ionic conductivity at room temperature is a problem. Therefore, various methods for improving low ionic conductivity at room temperature have been studied. In recent years, by combining with heterogeneous materials (polymer electrolytes), we have been manufacturing materials with improved ionic conductivity by improving the low ionic conductivity at room temperature. (Rani V Penumaka, May 27, 2015), a typical manufacturing process using a composite electrolyte with a polymer electrolyte is performed by adding an excess amount of a polymer electrolyte to form a slurry Discloses a process for preparing a membrane having a uniform thickness on a specific basement membrane, followed by drying and processing to finally separate the basement membrane to complete the composite electrolyte. However, the slurry viscosity control and coating conditions on the base membrane must be carefully controlled to obtain a solid electrolyte membrane of a desired shape and material, and physical disadvantage is inevitable under an excessive mechanical load.

Accordingly, the present inventors have combined the ceramic solid electrolyte with the PEO-based polymer electrolyte in order to overcome this disadvantage, and then produced a complex electrolyte using a simple forming process and a heat treatment process which do not require a base film. Since the composite electrolyte contains a polymer electrolyte, the ion conductivity is measured using an electrochemical impedance spectroscopy (EIS) without the necessity of sintering at a high temperature accompanied with the production of a solid electrolyte. The properties of the composite electrolyte To complete the present invention.

In this regard, Korean Patent Publication No. 10-2017-0010623 discloses a lithium secondary battery including a solid electrolyte.

An object of the present invention is to provide a composite electrolyte for a secondary battery, a method for producing the composite electrolyte, and a secondary battery comprising the composite electrolyte.

In order to achieve the above object,

A step (step 1) of obtaining a solid electrolyte powder represented by the following formula (1);

Mixing the obtained solid electrolyte powder with a polymer electrolyte to obtain a composite electrolyte molded body for a secondary battery (step 2); And

(3) preparing a composite electrolyte for a secondary battery by applying heat and pressure to the formed body;

Containing

A method for producing a composite electrolyte for a secondary battery is provided.

[Chemical Formula 1]

Li _{1 + x} Al _x M _{2 -x} (PO ₄ ) ₃

In the above formula (1), M is Ti or Ge, and 0 < x < 2.

In addition,

A composite electrolyte for a secondary battery manufactured by the above method is provided.

Also,

A solid electrolyte and a polymer electrolyte,

The solid electrolyte is represented by the following general formula (1)

Wherein the content of the polymer electrolyte is 45 to 75 parts by weight based on 100 parts by weight of the solid electrolyte,

Characterized in that the composite electrolyte is not subjected to high temperature sintering.

Thereby providing a composite electrolyte.

[Chemical Formula 1]

Li _{1 + x} Al _x M _{2 -x} (PO ₄ ) ₃

In the above formula (1), M is Ti or Ge, and 0 < x < 2.

In addition,

And a secondary battery including the composite electrolyte.

In addition,

And an electrochemical sensor including the composite electrolyte.

The composite electrolyte for a secondary battery comprising the solid electrolyte and the polymer electrolyte according to the present invention can be produced without the high temperature sintering step which is essential in the conventional solid electrolyte production process by including the polymer electrolyte in the manufacturing method , The content of the solid electrolyte is larger than that of the polymer electrolyte, so that it can have properties such as excellent mechanical strength and chemical resistance of the solid electrolyte.

1 is a schematic view showing a process for producing a composite electrolyte for a secondary battery according to the present invention,
FIG. 2 is a diagram illustrating a method for producing the solid electrolyte powder of the present invention and a method for producing a composite electrolyte using the same.
FIG. 3 is a graph (a) showing the result of X-ray diffraction pattern analysis of a solid electrolyte prepared by changing the heat treatment temperature of the solid electrolyte precursor powder of the present invention and a scanning electron microscope (SEM) Observed photograph (b)
FIG. 4 is a graph showing the results of analyzing ion conductivities of the composite electrolyte prepared in Example 1 according to the present invention,
FIG. 5 is a graph showing the results of analyzing ion conductivities of the composite electrolyte prepared in Example 2 according to the present invention,
6 is a graph showing the results of analyzing ion conductivity of the solid electrolyte prepared in Comparative Example 1 of the present invention by using pellets.

The present invention

A step (step 1) of obtaining a solid electrolyte powder represented by the following formula (1);

Mixing the obtained solid electrolyte powder with a polymer electrolyte to obtain a composite electrolyte molded body for a secondary battery (step 2); And

(3) preparing a composite electrolyte for a secondary battery by applying heat and pressure to the formed body;

Containing

A method for producing a composite electrolyte for a secondary battery is provided.

[Chemical Formula 1]

Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃

In the above formula (1), M is Ti or Ge, and 0 < x < 2.

Hereinafter, a method for producing a composite electrolyte for a secondary battery according to the present invention will be described in detail with reference to FIG.

First, step 1 is a step (S100) of obtaining the solid electrolyte powder represented by the above formula (1).

Step 1 may include the following steps S110 and S120.

First, a step (S110) of stirring and reacting a lithium salt, Ti and an Al precursor, and phosphoric acid to obtain a solid electrolyte precursor (S110).

In this case, the lithium salt is _{LiCH 3 COO, LiPF 6, LiBF} 4, LiSbF 6, LiAsF 6, LiCF 3 SO 3, LiN (SO 2 C 2 F 5) 2, LiN (CF 3 SO 2) 2, LiC 4 F _{9 SO 3, LiClO 4, LiAlO} 4, LiAlCl- 4, LiCl, LiI, LiB (C 2 O 4) 2, and including, but may be a lithium salt selected from the group consisting of the combinations thereof, limited to It is not.

Also, the reaction of step S110 may be performed at about 150 ° C to about 300 ° C, but is not limited thereto. For example, the reaction may be carried out at a temperature of about 150 캜 to about 300 캜, about 170 캜 to about 300 캜, about 190 캜 to about 300 캜, about 200 캜 to about 300 캜, From about 150 캜 to about 260 캜, from about 150 캜 to about 240 캜, from about 150 캜 to about 300 캜, from about 260 캜 to about 300 캜, from about 280 캜 to about 300 캜, But is not limited to, being carried out at a temperature of about 220 캜, about 150 캜 to about 200 캜, about 150 캜 to about 190 캜, or about 150 캜 to about 170 캜. When the reaction is carried out at a temperature lower than the above-mentioned temperature range, the solid electrolyte precursor may not be easily formed due to a lack of reaction. If the reaction is carried out at a temperature higher than the above-mentioned temperature range, an impurity phase other than the precursor may be contained.

The reaction of step S110 may be performed through a solvent thermal synthesis method, in which case a solvent may be added, but the present invention is not limited thereto. The solvent is preferably a dispersant, for example, an alcoholic organic solvent in which polyethylene glycol is dissolved at a predetermined concentration, a lithium salt such as 2-methoxyethanol, a Ti and Al precursor, and an alcoholic solvent in which phosphoric acid is soluble. Accordingly, the lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid can be self-polymerized in the solution of the lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid.

Next, the step (S120) of heat treating the solid electrolyte precursor to obtain the solid electrolyte represented by Formula 1 (S120).

At this time, the heat treatment in step S120 may be performed at about 400 ° C to about 600 ° C, but is not limited thereto. For example, the heat treatment may be performed at a temperature of from about 400 캜 to about 600 캜, from about 420 캜 to about 600 캜, from about 440 캜 to about 600 캜, from about 460 캜 to about 600 캜, From about 540 캜 to about 600 캜, from about 560 캜 to about 600 캜, from about 580 캜 to about 600 캜, from about 400 캜 to about 580 캜, from about 400 캜 to about 600 캜 From about 400 ° C to about 440 ° C, from about 400 ° C to about 540 ° C, from about 400 ° C to about 520 ° C, from about 400 ° C to about 500 ° C, from about 400 ° C to about 480 ° C, , Or about 400 &lt; 0 &gt; C to about 420 &lt; 0 &gt; C. When the heat treatment is performed at a temperature lower than the temperature range, the solid electrolyte represented by Formula 1 may not be obtained due to insufficient bonding of the lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid. It is possible to induce the formation of a secondary phase other than the phosphate-based electrolyte having a desired crystal structure or to induce excessive grain growth.

In addition, the heat treatment may be performed for about 3 hours to about 7 hours, preferably about 4 hours to about 6 hours, but is not limited thereto. When the heat treatment is performed for less than the above range, the solid electrolyte represented by Formula 1 may not be obtained due to insufficient bonding of the lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid, It is possible to induce the formation of a secondary phase other than the phosphate-based electrolyte having a desired crystal structure or to induce excessive grain growth.

Next, Step 2 is a step (S200) of obtaining a composite electrolyte formed body for a secondary battery by mixing the obtained solid electrolyte powder with a polymer electrolyte.

The polymer electrolyte may include, but is not limited to, a polymer selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide, glycidol, and combinations thereof.

The polymer electrolyte of step 2 may be further mixed with a plasticizer and a cross-linking agent, but the present invention is not limited thereto.

At this time, the plasticizer is used to provide flexibility for facilitating the molding of the polymer electrolyte and to improve the adhesion to the solid electrolyte. Examples of the plasticizer include polyethylene glycol dimethyl ether, ethylene carbonate, Propylene carbonate, butylene carbonate, vinylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, gamma butyrolactone, But are not limited to, plasticizers selected from the group consisting of gamma-butyrolactone, sulfolane, methylacetate, methylpropionate, and combinations thereof. It is not.

The crosslinking agent is added to promote crosslinking between the solid electrolyte and the polymer electrolyte. Examples of the crosslinking agent include 4,4 '- (propane-2,2-diyl) diphenol, polyethyleneglycol diacrylate, , Triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol A ethoxylate dimethacrylate, and combinations thereof. The term &quot; polymer &quot; But are not limited to, a cross-linking agent.

The amount of the plasticizer may be about 50 parts by weight to about 500 parts by weight based on 100 parts by weight of the crosslinking agent, but is not limited thereto. For example, the amount of the plasticizer may be about 50 parts by weight to about 500 parts by weight, about 80 parts by weight to about 500 parts by weight, about 100 parts by weight to about 500 parts by weight, about 150 parts by weight, About 500 parts by weight, about 200 parts by weight to about 500 parts by weight, about 250 parts by weight to about 500 parts by weight, about 300 parts by weight to about 500 parts by weight, about 350 parts by weight to about 500 parts by weight, About 500 parts by weight, about 450 parts by weight to about 500 parts by weight, about 50 parts by weight to about 450 parts by weight, about 50 parts by weight to about 400 parts by weight, about 50 parts by weight to about 350 parts by weight, about 50 parts by weight About 50 parts by weight to about 250 parts by weight, about 50 parts by weight to about 200 parts by weight, about 50 to about 150 parts by weight, about 50 to about 100 parts by weight, or about 50 parts by weight To about 80 parts by weight, but is not limited thereto. If the amount of the plasticizer is less than the above range, solid properties may be enhanced and ion conductivity may not be obtained. If the plasticizer content is above the above range, solidification may not be performed and a formed body of a desired size and shape may not be formed.

In addition, the composite electrolyte composite for a secondary battery obtained after the mixing may be molded into a pellet, but the present invention is not limited thereto.

The method may further include a step of mixing the solid electrolyte with the polymer electrolyte and then pressure-curing the mixture in the step 2, but the present invention is not limited thereto. By including the curing step, it is possible to achieve a solid-state composite electrolyte having ion conductivity while activating the crosslinking agent in the polymer electrolyte to proceed curing.

In addition, the curing step may be performed for about 1 hour to about 5 hours, preferably about 2 hours to about 4 hours, but is not limited thereto. If the curing step is carried out for less than the above range, the curing of the polymer electrolyte may be insufficient and the formation of the molded body may be incomplete. If the curing is carried out at the temperature range exceeding the above range, the polymer contained in the plasticizer and the cross- It can be unstable.

The polymer electrolyte may be used in an amount of 45 to 75 parts by weight based on 100 parts by weight of the solid electrolyte, but is not limited thereto. Since the content of the solid electrolyte is excessive relative to the content of the polymer electrolyte, the polymer electrolyte exhibits properties of a solid electrolyte mainly and thus has excellent mechanical strength, but is not limited thereto.

Next, Step 4 is a step (S300) of producing a composite electrolyte for a secondary battery by applying heat and pressure to the formed body.

By including the step of thermosetting, it is possible to achieve a solid-state composite electrolyte having ion conductivity while activating a crosslinking agent in the polymer electrolyte to promote curing, wherein the curing is performed at about 50 ° C to about 150 ° C But is not limited thereto. For example, the curing may be performed at a temperature of from about 50 캜 to about 150 캜, from about 80 캜 to about 150 캜, from about 100 캜 to about 150 캜, from about 120 캜 to about 150 캜, But is not limited to, performing at from 50 캜 to about 140 캜, from about 50 캜 to about 120 캜, from about 50 캜 to about 100 캜, or from about 50 캜 to about 80 캜. If the curing step is carried out below the temperature range, the curing of the polymer electrolyte may be insufficient and the formation of the molded body may be incomplete. If the curing step is carried out at a temperature exceeding the above temperature range, the polymer contained in the plasticizer and the cross- This can be unstable.

At this time, the pressure applied in step 3 may be about 100 MPa to about 400 MPa, but is not limited thereto. For example, the pressure may range from about 100 MPa to about 400 MPa, from about 150 MPa to about 400 MPa, from about 200 MPa to about 400 MPa, from about 250 MPa to about 400 MPa, from about 300 MPa to about 400 MPa, From about 100 MPa to about 300 MPa, from about 100 MPa to about 350 MPa, from about 100 MPa to about 300 MPa, from about 100 MPa to about 250 MPa, from about 100 MPa to about 200 MPa, or from about 100 MPa to about 150 MPa, But is not limited to. If the pressure is less than the above range, the bond between the solid electrolyte and the polymer electrolyte may be weakened. If the pressure is out of the above range, the molded body having a desired size and shape may not be retained.

In addition,

A composite electrolyte for a secondary battery manufactured by the above method is provided.

In addition,

A solid electrolyte and a polymer electrolyte,

The solid electrolyte is represented by the following general formula (1)

Wherein the content of the polymer electrolyte is 45 to 75 parts by weight based on 100 parts by weight of the solid electrolyte,

Characterized in that the composite electrolyte is not subjected to high temperature sintering.

Thereby providing a composite electrolyte.

[Chemical Formula 1]

Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃

In the above formula (1), M is Ti or Ge, and 0 < x < 2.

Hereinafter, the composite electrolyte according to the present invention will be described in detail.

First, the solid electrolyte may be formed of a lithium salt, a Ti or Ge precursor, an Al precursor, and phosphoric acid.

The lithium salt is selected from the group consisting of LiCH ₃ COO, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC ₄ F ₉ SO _{3, LiClO 4, LiAlO 4,} LiAlCl- 4, LiCl, LiI, LiB (C 2 O 4) 2, and including, but may be a lithium salt selected from the group consisting of the combinations thereof, but is not limited to, .

In addition, the polymer electrolyte may include, but is not limited to, a polymer selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide, glycidol, and combinations thereof.

The composite electrolyte for a secondary battery may further include a plasticizer and a crosslinking agent, but the present invention is not limited thereto.

At this time, the plasticizer is used to provide flexibility for facilitating the molding of the polymer electrolyte and to improve the adhesion to the solid electrolyte. Examples of the plasticizer include polyethylene glycol dimethyl ether, ethylene carbonate, Propylene carbonate, butylene carbonate, vinylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, gamma butyrolactone, But are not limited to, plasticizers selected from the group consisting of gamma-butyrolactone, sulfolane, methylacetate, methylpropionate, and combinations thereof. It is not.

The crosslinking agent is added to promote crosslinking between the solid electrolyte and the polymer electrolyte. Examples of the crosslinking agent include 4,4 '- (propane-2,2-diyl) diphenol, polyethyleneglycol diacrylate, , Triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol A ethoxylate dimethacrylate, and combinations thereof. The term &quot; polymer &quot; But are not limited to, a cross-linking agent.

The amount of the plasticizer may be about 50 parts by weight to about 500 parts by weight based on 100 parts by weight of the crosslinking agent, but is not limited thereto. For example, the amount of the plasticizer may be about 50 parts by weight to about 500 parts by weight, about 80 parts by weight to about 500 parts by weight, about 100 parts by weight to about 500 parts by weight, about 150 parts by weight, About 500 parts by weight, about 200 parts by weight to about 500 parts by weight, about 250 parts by weight to about 500 parts by weight, about 300 parts by weight to about 500 parts by weight, about 350 parts by weight to about 500 parts by weight, About 500 parts by weight, about 450 parts by weight to about 500 parts by weight, about 50 parts by weight to about 450 parts by weight, about 50 parts by weight to about 400 parts by weight, about 50 parts by weight to about 350 parts by weight, about 50 parts by weight About 50 parts by weight to about 250 parts by weight, about 50 parts by weight to about 200 parts by weight, about 50 to about 150 parts by weight, about 50 to about 100 parts by weight, or about 50 parts by weight To about 80 parts by weight, but is not limited thereto. If the amount of the plasticizer is less than the above range, solid properties may be enhanced and ion conductivity may not be obtained. If the plasticizer content is above the above range, solidification may not be performed and a formed body of a desired size and shape may not be formed.

In addition, the composite electrolyte may be in the form of pellets, but is not limited thereto.

The polymer electrolyte content may be 45 parts by weight to 75 parts by weight based on 100 parts by weight of the solid electrolyte, but is not limited thereto. Since the content of the solid electrolyte is excessive relative to the content of the polymer electrolyte, the polymer electrolyte exhibits properties of a solid electrolyte mainly and thus has excellent mechanical strength, but is not limited thereto.

The polymer electrolyte may be dispersed throughout the solid electrolyte.

In addition,

And a secondary battery including the composite electrolyte.

Hereinafter, a secondary battery including the composite electrolyte of the present invention will be described in detail.

The secondary battery may include, but is not limited to, a lithium secondary battery, a nickel cadmium battery, a nickel metal hydride battery, or a lead acid battery.

When the secondary battery is a lithium secondary battery, the lithium secondary battery is a positive electrode; A negative electrode disposed apart from the positive electrode and comprising lithium metal; And a composite electrolyte for a lithium secondary battery interposed between the positive electrode and the negative electrode, wherein the composite electrolyte for a lithium secondary battery comprises:

A solid electrolyte and a polymer electrolyte,

The solid electrolyte is represented by the following general formula (1)

The polymer electrolyte content is 45 to 75 parts by weight based on 100 parts by weight of the solid electrolyte,

The composite electrolyte for a lithium secondary battery is not subjected to sintering.

[Chemical Formula 1]

Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃

In the above formula (1), M is Ti or Ge, and 0 < x < 2.

At this time, in the lithium secondary battery, the positive electrode is formed on the positive electrode collector, and the lithium transition metal oxide may be included as the positive electrode active material, but the present invention is not limited thereto. As the cathode current collector, a porous body such as a mesh or mesh shape may be used, and a porous metal plate such as stainless steel, nickel, aluminum, or the like may be used, but not limited thereto, and any material that can be used as a collector in the related art It is possible. In addition, the cathode current collector may be coated with a metal or an alloy coating having oxidation resistance to prevent oxidation.

In the positive electrode, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) may be used as the positive electrode active material. Specifically, a lithium-containing transition metal oxide may be used. More specifically, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (NiaCobMnc) O ₂ (0 <a < 0 <c <1, a + b + c = 1), LiNi 1 - y Co y O 2, LiCo 1 - y Mn y O 2, LiNi 1 - y Mn y O 2 (O≤y <1), Li _{(Ni a Co b Mn c)} O4 (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn 2 - z Ni z O 4, LiMn 2 - z But are not limited to, materials selected from the group consisting of Co _z O ₄ (0 <z <2), LiCoPO ₄ , LiFePO ₄ , and combinations thereof. In addition to the above oxide, sulfide, selenide, and halide may be used, but the present invention is not limited thereto. In addition, Li-free cathode active materials may be initially used, for example, TiS ₂ , FeS _2, or V ₂ O _5. However, the present invention is not limited thereto.

In addition, the anode may include, but is not limited to, a conductive material. In this case, the conductive material may be porous. Therefore, any conductive material having porosity and conductivity may be used without limitation, and for example, a carbon-based material having porosity may be used.

Such carbon-based materials may include, but are not limited to, materials selected from the group consisting of carbon black, graphite, graphene, activated carbon, carbon fibers, and combinations thereof. Examples of the conductive material include metallic conductive materials such as metal fibers and metal mesh; Metallic powder such as copper, silver, nickel, and aluminum; Or an organic conductive material such as a polyphenylene derivative can also be used. The conductive materials may be used alone or in combination.

In addition, the anode may further include a binder, but is not limited thereto. As the binder, a thermoplastic resin or a thermosetting resin can be used. More specifically, examples of the binder include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, Vinylidene-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, Propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer A copolymer selected from the group consisting of ethylene-acrylic acid copolymer, and combinations thereof. It may be using, but not limited thereto as long as they can all be used as binders in the art.

The positive electrode may be prepared by mixing a positive electrode active material, a conductive material, and optionally a binder to prepare a composition for forming a positive electrode active material layer, coating the positive electrode active material on at least one surface of the positive electrode current collector, and drying and rolling. As another method, the composition for forming a cathode active material layer may be cast on a separate support, and then a film obtained by peeling the support from the support may be laminated on the cathode current collector.

Meanwhile, in the lithium secondary battery, the negative electrode may include lithium metal as a negative electrode active material capable of intercalating and deintercalating lithium. Lithium metal is useful as a negative electrode of a lithium secondary battery having a high energy density and excellent discharge capacity holding characteristics because of low density and low standard reduction potential.

Further, in the lithium secondary battery, a composite electrolyte for a lithium secondary battery may be interposed between the positive electrode and the negative electrode. The composite electrolyte may act as an electrolyte and a separation membrane in a lithium secondary battery.

The composite electrolyte for a lithium secondary battery includes

A solid electrolyte and a polymer electrolyte,

The solid electrolyte is represented by the following general formula (1)

The polymer electrolyte content is 45 to 75 parts by weight based on 100 parts by weight of the solid electrolyte,

The composite electrolyte for a lithium secondary battery is characterized in that it is not subjected to sintering.

[Chemical Formula 1]

Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃

In the above formula (1), M is Ti or Ge, and 0 < x < 2.

At this time, the solid electrolyte may be formed by a lithium salt, Ti or Ge precursor, Al precursor, and phosphoric acid.

The lithium salt is selected from the group consisting of LiCH ₃ COO, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC ₄ F ₉ SO _{3, LiClO 4, LiAlO 4,} LiAlCl- 4, LiCl, LiI, LiB (C 2 O 4) 2, and including, but may be a lithium salt selected from the group consisting of the combinations thereof, but is not limited to, .

In addition, the polymer electrolyte may include, but is not limited to, a polymer selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide, glycidol, and combinations thereof.

The composite electrolyte for a lithium secondary battery may further include a plasticizer and a crosslinking agent, but the present invention is not limited thereto.

The plasticizer is used as a medium capable of conducting lithium ions. Examples of the plasticizer include polyethyleneglycol dimethyl ether, ethylene carbonate, propylene carbonate, butylene carbonate, But are not limited to, vinylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, sulfolane, but are not limited to, a plasticizer selected from the group consisting of methylacetate, methylpropionate, and combinations thereof.

The crosslinking agent is added to promote crosslinking between the solid electrolyte and the polymer electrolyte. Examples of the crosslinking agent include 4,4 '- (propane-2,2-diyl) diphenol, polyethyleneglycol diacrylate, , Triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol A ethoxylate dimethacrylate, and combinations thereof. The term &quot; polymer &quot; But are not limited to, a cross-linking agent.

The amount of the plasticizer may be about 50 parts by weight to about 500 parts by weight based on 100 parts by weight of the crosslinking agent, but is not limited thereto. For example, the amount of the plasticizer may be about 50 parts by weight to about 500 parts by weight, about 80 parts by weight to about 500 parts by weight, about 100 parts by weight to about 500 parts by weight, about 150 parts by weight, About 500 parts by weight, about 200 parts by weight to about 500 parts by weight, about 250 parts by weight to about 500 parts by weight, about 300 parts by weight to about 500 parts by weight, about 350 parts by weight to about 500 parts by weight, About 500 parts by weight, about 450 parts by weight to about 500 parts by weight, about 50 parts by weight to about 450 parts by weight, about 50 parts by weight to about 400 parts by weight, about 50 parts by weight to about 350 parts by weight, about 50 parts by weight About 50 parts by weight to about 250 parts by weight, about 50 parts by weight to about 200 parts by weight, about 50 to about 150 parts by weight, about 50 to about 100 parts by weight, or about 50 parts by weight To about 80 parts by weight, but is not limited thereto. If the content of the plasticizer is less than the above range, the curing of the polymer electrolyte will occur excessively and the ionic conductivity may be remarkably reduced. If the content is more than the above range, the curing will be insufficient.

In addition, the composite electrolyte for a lithium secondary battery may be in the form of pellets, but is not limited thereto.

The polymer electrolyte content may be 45 parts by weight to 75 parts by weight based on 100 parts by weight of the solid electrolyte, but is not limited thereto. Since the content of the solid electrolyte is excessive relative to the content of the polymer electrolyte, the polymer electrolyte exhibits properties of a solid electrolyte mainly and thus has excellent mechanical strength, but is not limited thereto.

In addition,

And an electrochemical sensor including the composite electrolyte.

The electrochemical sensor is a sensor that detects the concentration of a specific substance through a change in current or voltage. Sensing by electrochemical method is advantageous in that it can be detected immediately at low concentration and can be easily designed in any size.

Generally, the electrochemical sensor may include an anode and a cathode where an electrochemical reaction takes place, and a conductor therebetween.

In the present invention, the conductor may be a composite electrolyte, and the composite electrolyte is as described above.

Hereinafter, examples and experimental examples of the present invention will be described in more detail.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the present invention is not limited by the following Examples and Experimental Examples.

&Lt; Preparation Example > Preparation of solid electrolyte

0.1412 g of lithium acetate and 0.0756 g of aluminum nitrate hydrate were sufficiently dissolved in 20 mL of 2-methoxyethanol and stirred. Then, add 2 mL of polyethylene glycol, 0.6223 mL of titanium butoxide and 0.2142 mL of phosphoric acid and stir well. The solution was transferred to a Teflon container for microwave reactor to proceed with the solvent thermo-synthesis, and microwave scanning was performed at 200 ° C for 10 minutes. The solvent was then removed via centrifugation and sufficiently dried in an oven to obtain a precursor powder.

The precursor powder to obtain 525 ℃ at a heating rate of 5 per minute ℃ to put in an alumina boat using an electric furnace in a hydrogen atmosphere with 5% heat-treated for 5 hours Li _{1. 3} Al _{0 . 3} Ti _{1 . 7} (PO ₄ ) ₃ .

< Example  1> Li _{One . 3} Al _{0 . 3} Ti _{One .7} (PO ₄ ) ₃  And a composite electrolyte containing a polymer electrolyte

Bis (trifluoromethane) sulfonimide lithium salt, CF ₃ (trifluoromethanesulfonylimide) lithium salt was added to 190.5 μL of polyethylene glycol dimethyl ether (CH ₃ O (CH ₂ CH ₂ O) _n CH ₃ ) SO ₂ NLiSO ₂ CF ₃ ) and 43.5 μL of bisphenol A (4,4 '- (propane-2,2-diyl) diphenol, C ₁₅ H ₁₆ O ₂ ) were dissolved in 75% tetra- (Polyethylene glycol dimethyl ether: bisphenol A = 8: 2) prepared by mixing 0.0005 g of a crosslinking agent dissolved in 75% Tert-Butyl peroxypivalate (C ₉ H ₁₈ O ₃ ) was mixed with 250 μL of a poly And 0.4 g of Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ were thoroughly mixed. The pellets were then shaped into molds and cured at 80 ° C for more than 3 hours. Subsequently, the cured molded body was further subjected to a pressure of 200 to 300 MPa for 2 minutes to form a thickness of 0.1 to 0.5 cm and a diameter of 1.5 cm.

Impedance was measured by attaching a copper wire to both sides of the pellet using the carbon tape and carbon paste. The experimental conditions were 10 mV, 100 Hz to 300 KHz, and 30 to 100 ° C.

< Example  2> Li _{One . 3} Al _{0 . 3} Ti _{One .7} (PO ₄ ) ₃  And a composite electrolyte containing a polymer electrolyte

The polymer electrolyte of Example 1 was dissolved in 95.2 μL of polyethylene glycol dimethyl ether (CH ₃ O (CH ₂ CH ₂ O) _n CH ₃ ) in the presence of a bis (trifluoromethane) sulfonimide lithium salt (Bis _{trifluoromethane) sulfonimide lithium salt, CF 3} SO 2 NLiSO 2 CF 3) 0.0546 g of the plasticizer and the dissolved bisphenol a (4,4 '- (propane-2,2 -diyl) diphenol, C 15 H 16 O 2) in 130.4 μL A composite electrolyte was prepared in the same manner as in Example 1 except that a crosslinking agent in which 0.0015 g of 75% tetra-butyl peroxypivalate (C ₉ H ₁₈ O ₃ ) was dissolved was prepared Polyethylene glycol dimethyl ether: bisphenol A = 4: 6).

&Lt; Comparative Example > Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃  Solid electrolyte production

0.1765 g of lithium acetate and 0.0946 g of aluminum nitrate hydrate were sufficiently dissolved in 25 mL of 2-methoxyethanol and stirred. Then, add 2.5 mL of polyethylene glycol, 0.7779 mL of titanium butoxide, 0.2677 mL of phosphoric acid and stir well. The solution was transferred to a Teflon container for microwave reactor to proceed with the solvent thermo-synthesis, and microwave scanning was performed at 200 ° C for 10 minutes. The solvent was then removed via centrifugation and sufficiently dried in an oven to obtain a precursor powder.

The precursor powder to obtain 525 ℃ at a heating rate of 5 per minute ℃ to put in an alumina boat using an electric furnace in a hydrogen atmosphere with 5% heat-treated for 5 hours Li _{1. 3} Al _{0 . 3} Ti _{1 . 7} (PO ₄ ) ₃ .

The Li _{1 . 3} Al _{0 . 3} Ti _{1 .7} (PO ₄ ) ₃ was put into a mold and pressure was applied at 370 MPa for 5 minutes to form a pellet having a thickness of 0.17 cm and a diameter of 1.44 cm. The pellet was then subjected to CIP treatment and then heated at a rate of 950 Lt; 0 &gt; C and 5% hydrogen atmosphere for 2 hours.

Impedance was measured by attaching a copper wire to carbon pellets on both sides of the pellet. The experimental conditions were 10 mV, 1 Hz to 1 MHz.

< Experimental Example > Li _{One . 3} Al _{0 . 3} Ti _{One .7} (PO ₄ ) ₃  And Characterization of Composite Electrolyte Containing Polymer Electrolyte

After heat treatment Li _{1 . 3} Al _{0 . 3} Ti _{1 . 7} (PO ₄ ) ₃ was measured by XRD and SEM to confirm the phase and shape of Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ .

The crystal structure and impurity formation of the phosphate-based ceramic electrolyte using the XRD measurement method are shown in FIG. As a result, it was confirmed that the Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ phase was not formed in the sample subjected to the heat treatment at 400 ° C. or lower, and it was confirmed that the phosphate-based ceramic compound having a desired crystal structure was formed at 400 ° C. or higher .

The surface morphology and particle size distribution of the phosphate-based ceramic electrolyte using the SEM measurement method are shown in FIG. 3B. As a result, it was confirmed that the primary shape was irregular in size and shape, and the secondary shape had a particle size of several tens nm, and the particle size was uniformly formed.

In addition, the ion conductivity according to the temperature of the composite electrolyte prepared in Example 1 is shown in FIGS. 4A and 4B, and it was confirmed that the ion conductivity increases with increasing temperature.

The composite electrolyte prepared in Example 2 was also analyzed by ionic conductivity according to the temperature, and shown in FIGS. 5A and 5B, and showed the same tendency as the composite electrolyte prepared in Example 1, but exhibited a higher ionic conductivity at the same temperature .

The solid electrolyte prepared in Comparative Example 1 was analyzed for ionic conductivity at room temperature and shown in FIG. 6, and it was confirmed that unlike the complex electrolyte prepared in Examples 1 and 2, the impedance signal was unstable and ion conductivity could not be evaluated I could.

Claims (12)

A step (step 1) of obtaining a solid electrolyte powder represented by the following formula (1);
Mixing the obtained solid electrolyte powder with a polymer electrolyte mixed with a plasticizer including a polymer and a crosslinking agent to obtain a composite electrolyte molded body for a secondary battery (Step 2); And
(3) preparing a composite electrolyte for a secondary battery by thermally curing the molded body at a temperature of 50 to 150 캜 and applying pressure thereto;
Containing
Method for producing composite electrolyte for secondary battery:
[Chemical Formula 1]
Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃
(M in the above formula (1) is Ti or Ge, and 0 < x < 2).
The method according to claim 1,
Wherein the polymer electrolyte comprises a polymer selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide, glycidol, and combinations thereof.
delete The method according to claim 1,
The plasticizer may be at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl &lt; RTI ID = 0.0 &gt; A plasticizer selected from the group consisting of ethylmethyl carbonate, gamma-butyrolactone, sulfolane, methylacetate, methylpropionate, and combinations thereof, By weight based on the total weight of the composite electrolyte.
The method according to claim 1,
The crosslinking agent may be selected from the group consisting of polyethyleneglycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol A (meth) acrylate, bisphenol A ethoxylate dimethacrylate), and combinations thereof. The method for producing a composite electrolyte for a secondary battery according to claim 1,
The method according to claim 1,
Wherein the amount of the plasticizer is 50 parts by weight to 500 parts by weight based on 100 parts by weight of the crosslinking agent.
The method according to claim 1,
And a step of mixing the solid electrolyte with the polymer electrolyte and then pressure-curing the polymer electrolyte in the step 2.
The method according to claim 1,
Wherein the content of the polymer electrolyte is 45 parts by weight to 75 parts by weight with respect to 100 parts by weight of the solid electrolyte.
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