WO2017074116A1 - Polymer electrolyte having multi-layer structure, and all-solid battery comprising same - Google Patents

Abstract

The present invention relates to a polymer electrolyte for an all-solid battery, having a multi-layer structure and, more particularly, to a polymer electrolyte having a multi-layer structure, which comprises a first polymer electrolyte layer and a second polymer electrolyte layer, wherein the EO:Li molar ratio of a poly(ethylene oxide)(PEO)-based polymer and a lithium salt is different between the first and second polymer electrolyte layers. The application of the solid polymer electrolyte of the present invention to the all-solid battery can remarkably reduce the interfacial resistance with lithium and the discharge overvoltage, resulting in a sufficient discharge capacity, and can improve output characteristics and energy density.

Description

Polymer electrolyte having a multilayer structure and an all-solid-state battery comprising the same

This application claims the benefit of priority based on Korean Patent Application No. 10-2015-0151630 filed on October 30, 2015 and Korean Patent Application No. 10-2016-0141786 filed on October 28, 2016. All content disclosed in the literature is included as part of this specification.

The present invention relates to a polymer electrolyte for an all-solid-state battery having a multi-layer structure, and more specifically, the EO: Li molar ratio of a polyethylene oxide (PEO) -based polymer and a lithium salt is A multi-layered polymer electrolyte comprising different first polymer electrolyte layers and second polymer electrolyte layers.

2. Description of the Related Art In recent years, secondary batteries have been increasing in demand for various applications as power sources for PCs, video cameras, mobile phones, and the like, or as power sources for electric vehicles and power storage media. Among the secondary batteries, especially lithium-based secondary batteries have higher capacity density than other secondary batteries and can operate at high voltage, and thus are used in information-related devices and communication devices as secondary batteries for compact and lightweight, and have recently been used for electric vehicles and hybrid vehicles. The development of high power and high capacity lithium-based secondary batteries is in progress.

A typical lithium-based secondary battery is composed of an electrolyte containing a positive electrode (positive electrode, cathode), a negative electrode (negative electrode, anode) and a lithium salt interposed therebetween, and such an electrolyte is a non-aqueous liquid electrolyte or a solid electrolyte. When a non-aqueous liquid electrolyte is used for the electrolyte, since the electrolyte penetrates into the positive electrode, an interface between the positive electrode active material constituting the positive electrode and the electrolyte tends to be formed, and thus has high electrical performance.

However, since a lithium secondary battery uses a flammable organic solvent in the liquid electrolyte, it is necessary to install a safety device in order to prevent ignition and rupture that may occur due to overcurrent due to a short circuit. It is also built. In addition, in order to prevent such a phenomenon, there may be a restriction in selecting a battery material or designing a battery structure.

Therefore, development of the all-solid-state battery which uses a solid electrolyte instead of a liquid electrolyte is advanced. Since an all-solid-state battery does not contain a flammable organic solvent, it has the advantage of simplifying a safety device, and is recognized as a battery excellent in manufacturing cost and productivity. Moreover, since it is easy to stack a junction structure including a pair of electrode layers including an anode (positive electrode) layer and a cathode (negative electrode) layer and a solid electrolyte layer sandwiched between these electrode layers, it is stable and has a high capacity, In addition, it is expected as a technology that can produce a battery of high power.

On the other hand, in an all-solid-state battery, it is known that the contact resistance between the particles of the active material particles responsible for the battery reaction and between the active material particles and the solid electrolyte particles greatly influence the internal resistance of the battery. In particular, as the volume change of the active material occurs with repeated charge and discharge, the contact between the active material and the solid electrolyte, the conductive material, and the like decreases, and there is a tendency that an increase in internal resistance, a decrease in capacity, and the like tend to occur. Therefore, various techniques have been proposed to improve the contact between the particles of the active material and the solid electrolyte and to suppress the increase in internal resistance.

For example, there is an attempt to improve the performance of an all-solid-state battery by paying attention to the interface between the cathode active material and the solid electrolyte material. For example, Narumi Ohta et al., "LiNbO ₃ -coated LiCoO ₂ as cathode material for all solid-state lithium secondary batteries", Electrochemistry Communications 9 (2007), 1486 ~ 1490, is applied to the surface of LiCoO ₂ (anode active material). LiNbO ₃ (Lithium niobate) is described as the material to be coated. This technique is to obtain a high power battery in such a manner as to reduce the interface resistance between the surface of LiCoO ₂ is coated with LiNbO _3, LiCoO ₂ as solid by suppressing the reaction between the electrolyte material, the solid electrolyte material and LiCoO _2.

In addition, when the negative electrode active material reacts with the solid electrolyte material, a high resistance portion is generally formed on the surface of the negative electrode active material, thereby increasing the interface resistance between the negative electrode active material and the solid electrolyte material. In order to solve this problem, Japanese Laid-Open Patent Publication No. 2004-206942 discloses a second solid electrolyte layer which does not chemically react with the first solid electrolyte and has lower ion conductivity than the first solid electrolyte layer (sulfide-based solid electrolyte material). Disclosed is an all-solid-state battery formed between the first solid electrolyte layer and a cathode made of metallic lithium. This is to suppress the reaction between the first solid electrolyte layer and the metal lithium through the formation of a second solid electrolyte layer having low ion conductivity.

However, attempts to improve the performance of such all-solid-state batteries do not reduce the interfacial resistance between the positive electrode or negative electrode active material and the solid electrolyte material, which is not suitable for the production of high-output, high-capacity batteries.

[Preceding technical literature]

[Patent Documents]

(Patent Document 1) Korean Unexamined Patent Publication No. 2012-0092918 "Polymer composite electrolyte for lithium secondary battery and lithium secondary battery comprising same"

(Patent Document 2) Japanese Unexamined Patent Publication No. 2004-206942 "All-solid-state lithium battery"

[Non-Patent Documents]

(Non-Patent Document 1) Qian, Jiangfeng, et al. "High rate and stable cycling of lithium metal anode." Nature communications 6 (2015)

(Non-Patent Document 2) "LiNbO3-coated LiCoO2 as cathode material for all solid-state lithium secondary batteries", Electrochemistry Communications 9 (2007), 1486-1490.

An all-solid-state battery to which a solid polymer electrolyte is applied is hard to express sufficient output or capacity at room temperature but also at 60 ° C or 80 ° C. The reasons for this are firstly low ionic conductivity of the polymer electrolyte and secondly, interfacial resistance between lithium and the polymer electrolyte. Although many efforts have been made to solve the ionic conductivity of the polymer electrolyte, there has been no significant improvement in ionic conductivity, and it has been pointed out as a limitation of the solid polymer electrolyte.

On the other hand, according to the prior literature, studies have been reported that a high concentration of electrolytes have low reactivity with lithium and low interfacial resistance in a battery using a liquid electrolyte and lithium metal (Qian, Jiangfeng, et al. "High rate and stable cycling of lithium metal anode. "Nature communications 6 (2015)). In light of this, the inventors have completed the present invention by applying a polymer electrolyte using a high concentration of lithium salt to an all-solid-state battery in order to lower the interfacial resistance between lithium and a solid polymer electrolyte.

Accordingly, an object of the present invention is to provide a polymer electrolyte for an all-solid-state battery which significantly lowers the interface resistance between lithium and a polymer electrolyte.

The present invention provides a polymer electrolyte layer having a molar ratio of EO: Li of a polyethylene oxide (PEO) -based polymer and a lithium salt of 1: 1 to 7: 1; And

A second polymer electrolyte layer having a molar ratio of EO: Li of the polyethylene oxide polymer and the lithium salt of 30: 1 to 8: 1;

It provides a polymer electrolyte for an all-solid-state battery comprising a multi-layer structure.

In this case, the thickness of the first polymer electrolyte layer may be 1 to 5 μm.

At this time, the thickness of the second polymer electrolyte layer may be 5 ~ 50 ㎛.

In this case, the weight average molecular weight (Mw) of the polyethylene oxide polymer may be 1,000,000 to 8,000,000.

At this time, the lithium salt is LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li , CF ₃ SO ₃ Li, LiSCN, LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carbonate, lithium 4-phenyl borate, It may include one selected from imides and combinations thereof.

In this case, the second polymer electrolyte layer may be cross-linked by a crosslinkable monomer to form a semi-interpenetrating polymer network (semi-IPN).

In this case, the crosslinkable monomer may include a — (CH ₂ —CH ₂ —O) —repeating unit.

In this case, the crosslinkable monomer may include 2 to 8 alkylenically unsaturated bonds at the terminals.

In this case, the crosslinkable monomer may be included in an amount of 5 to 50 wt% based on the polyethylene oxide polymer and the lithium salt.

In addition, the present invention is an all-solid-state battery comprising a positive electrode, a negative electrode and a solid polymer electrolyte interposed therebetween,

The solid polymer electrolyte provides an all-solid-state battery, which is a polymer electrolyte for an all-solid-state battery having the multilayer structure.

In this case, the first polymer electrolyte layer may be disposed to face the cathode.

When the solid polymer electrolyte of the present invention is applied to an all-solid-state battery, the interfacial resistance with lithium and the discharge overvoltage are significantly reduced, resulting in sufficient discharge capacity and improved output characteristics and energy density.

1 is a graph showing the interfacial resistance of a lithium metric battery according to Comparative Example 1. FIG.

2 is a graph showing the interfacial resistance of the lithium symmetric battery according to Example 1. FIG.

3 is a cross-sectional comparison diagram of the all-solid-state battery according to Comparative Example 2 (a) and Example 2 (b).

4 is a graph comparing discharge capacities of all-solid-state batteries according to Comparative Example 2 (a) and Example 2 (b).

As the lithium secondary battery of the present invention, the solid polymer electrolyte applied to an all-solid-state battery includes a polyethylene oxide (PEO) -based polymer and a lithium salt, and the EO: Li molar ratio of the polyethylene oxide-based polymer and the lithium salt is A multi-layered polymer electrolyte comprising a different first polymer electrolyte layer and a second polymer electrolyte layer is disclosed. Hereinafter, each component of the polymer electrolyte of the present invention will be described in detail.

First polymer electrolyte layer

In the present invention, the first polymer electrolyte layer is applied to lower the interfacial resistance, and the EO: Li molar ratio of the polyethylene oxide polymer and the lithium salt is selected and prepared within the range of 1: 1 to 7: 1. As described above, when the lithium salt is doped at a high rate and thinned to a thickness of 1 to 5 μm, the ion conductivity is slightly lowered, but the interface resistance can be significantly lowered.

Second polymer electrolyte layer

In the present invention, the second polymer electrolyte layer is applied to prevent the phenomenon caused by the generation of dendrite by increasing the mechanical strength, and the molar ratio of EO: Li of the polyethylene oxide polymer and the lithium salt is 30: 1 to 8: 1 It selects and manufactures in the range. In this case, the thickness of the second polymer electrolyte layer may be 5 to 50 μm.

In addition, the second polymer electrolyte layer may be crosslinked by a crosslinkable monomer to form a semi-interpenetrating polymer network (semi-IPN) structure. The semi-IPN structure can increase the strength of the solid polymer electrolyte, and the higher the strength, the more physically it can suppress the generation of lithium dendrites on the electrode surface. At this time, the weight average molecular weight (Mw) of the polyethylene oxide-based polymer may form a more dense semi-IPN structure when a relatively high molecular weight is applied within the range of 1,000,000 to 8,000,000.

The crosslinkable monomer may be a bifunctional or more than one polyfunctional monomer, and may include a-(CH ₂ -CH ₂ -O) -repeat unit, and may form an alkylenically unsaturated bond within the range of 2 to 8 polymerizable at both ends. It is preferable to include. The alkylenically unsaturated bond is a hydrocarbon group including at least one carbon-carbon double bond or triple bond, an ethenyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 1-butenyl group, 2-butenyl group, ethynyl group, 1-propynyl group, 1-butynyl group, 2-butynyl group, and the like, but are not limited thereto. Such alkylenically unsaturated bonds act as a crosslinking point to form a semi-IPN structure by crosslinking the polyethylene oxide polymer through a polymerization process.

For example, the crosslinkable monomer may include polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), polypropylene glycol diacrylate (Poly ( propylene glycol diacrylate: PPGDA), poly (propylene glycol) dimethacrylate (PPGDMA) and combinations thereof, and preferably polyethylene glycol diacrylate (PEGDA). .

In addition, the crosslinkable monomer is preferably included in the range of 5 to 50 wt% based on the weight of the polyethylene oxide-based polymer to form a semi-IPN structure suitable for the purpose of the present invention.

There is no restriction | limiting in particular in the method of the said crosslinkable monomer crosslinking between the said polyethylene oxide type polymers, Preferably, after adding a thermal initiator, it can crosslinking, maintaining suitable temperature conditions. In this case, benzoyl peroxide (BPO) or azobisisobutyronitrile (AIBN) may be applied as the thermal initiator.

Lithium salts commonly applied to the first polymer electrolyte layer and the second polymer electrolyte layer according to the present invention may be dissociated into lithium ions to penetrate into the first polymer electrolyte layer and the second polymer electrolyte layer and move freely. At this time, it is possible to operate a basic lithium battery as a source of lithium ions, and any lithium salt can be used as long as it is commonly used in lithium batteries, but preferably LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiSCN, LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic lithium carbonate, lithium 4-phenyl borate, imide and combinations thereof, but more preferably Lithium bis (fluorosulfonyl) imide (LiFSI), preferably represented by (FSO ₂ ) ₂ NLi, is possible.

The manufacturing method of the first polymer electrolyte layer or the second polymer electrolyte layer of the present invention is not limited in the present invention, and a mixing and molding process may be used by a wet or dry method as is known. In addition, the thickness of the solid polymer electrolyte of the present invention may be selectively prepared within the range of 1 to 50 ㎛.

Hereinafter, an all-solid-state battery including the solid polymer electrolyte of the present invention interposed between a positive electrode and a negative electrode, will be described an all-solid-state battery in which the first polymer electrolyte layer faces the negative electrode and the interface resistance is significantly reduced.

All-solid-state battery

The electrode active material may be a positive electrode active material when the electrode proposed in the present invention is a positive electrode, a negative electrode active material when the negative electrode. At this time, each electrode active material can be any active material applied to a conventional electrode, and is not particularly limited in the present invention.

The positive electrode or negative electrode active material used in the present invention varies depending on the type of conductive ions of the intended all-solid-state battery. For example, when the all-solid-state battery according to the present invention is an all-solid lithium secondary battery, the positive or negative electrode active material occludes or releases lithium ions. In addition, the positive electrode or negative electrode active material used in the present invention can generally react with the solid electrolyte material described above to form a high resistance portion.

The positive electrode active material may vary depending on the use of the lithium secondary battery, and the specific composition uses a known material. For example, any one selected from the group consisting of lithium-phosphate-iron compound, lithium cobalt-based oxide, lithium manganese-based oxide, lithium copper oxide, lithium nickel-based oxide and lithium manganese composite oxide, lithium-nickel-manganese-cobalt-based oxide And lithium transition metal oxides. More specifically, in the lithium metal phosphate represented by Li _{1 + a} M (PO _4-b ) X _b , M is at least one selected from metals of Groups 2 to 12, and X is F, S and As at least 1 type selected from N, it is preferable that they are -0.5 <= <= 0.5, and 0 <= b <= 0.1.

In this case, the negative electrode active material may be one selected from the group consisting of lithium metal, lithium alloy, lithium metal composite oxide, lithium-containing titanium composite oxide (LTO), and combinations thereof. At this time, the lithium alloy may be an alloy consisting of lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn. In addition, the lithium metal composite oxide is any one metal (Me) oxide (MeO _x ) selected from the group consisting of lithium and Si, Sn, Zn, Mg, Cd, Ce, Ni, and Fe, for example, Li _x Fe ₂ O ₃ (0 <x ≦ 1) or Li _x WO ₂ (0 <x ≦ 1).

In this case, if necessary, a conductive material, a polymer electrolyte, a binder, a filler, and the like may be further added to the active material, and the conductive material is not particularly limited as long as it has conductivity without causing chemical changes to the battery. For example, graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Specific examples of commercially available conductive materials include Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack and EC Armak, which are acetylene black series. Company (Armak Company), Vulcan XC-72 Cabot Company, Super P (manufactured by Timcal), and the like can be used.

The binder is a component that assists in bonding the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly Propylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, and the like.

The filler is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.

During charge and discharge operation of the battery, a high resistance portion is created at the interface between the electrode active material and the solid polymer electrolyte material. Accordingly, when the first polymer electrolyte layer and the second polymer electrolyte layer according to the present invention are used to form an all-solid-state battery, the interfacial resistance to movement of ions across the interface between the electrode active material and the solid electrolyte material is reduced. Since it becomes possible to reduce, it becomes possible to suppress the reduction in output.

The first polymer electrolyte layer is disposed to face the negative electrode, and a second polymer electrolyte layer is formed thereon, and an anode is formed thereon. If the stacking order of the first and second polymer electrolyte layers is reversed, the resistance of the battery may increase and the discharge capacity may decrease, which is not preferable.

In addition, using two polymer electrolyte layers having different EO: Li molar ratios of the polyethylene oxide polymer and the lithium salt, that is, the first ratio wherein the molar ratio of EO: Li of the polyethylene oxide polymer and the lithium salt is from 1: 1 to 7: 1 It is preferable to simultaneously apply the polymer electrolyte layer, the polyethylene oxide polymer and the second polymer electrolyte layer having a molar ratio of EO: Li of lithium salt of 30: 1 to 8: 1. If the first polymer electrolyte layer is out of the above range, the interfacial resistance may increase and the discharge capacity may be lowered, and if the second polymer electrolyte layer is out of the above range, the resistance of the electrolyte-separation membrane layer may increase. Discharge capacity may be lowered, which is undesirable.

The manufacture of an all-solid-state battery is a dry compression process in which an electrode and a solid electrolyte are prepared in powder form, and then put into a predetermined mold and pressed, or a slurry coating is prepared after coating and drying in the form of a slurry composition containing an active material, a solvent, and a binder. It is manufactured through the process. The production of the all-solid-state battery having the above configuration is not particularly limited in the present invention, and a known method can be used.

In one example, a solid electrolyte is disposed between the positive electrode and the negative electrode and then compression molded to assemble the cell. The assembled cell is installed in an outer packaging material and sealed by heat compression. As the exterior material, laminate packs such as aluminum and stainless steel and cylindrical or rectangular metal containers are very suitable.

The method of coating the electrode slurry on the current collector is a method of distributing the electrode slurry on the current collector and then uniformly dispersing it using a doctor blade or the like, die casting, comma coating. , Screen printing, and the like. In addition, the electrode slurry may be bonded to the current collector by pressing or lamination after molding on a separate substrate. At this time, by adjusting the concentration of the slurry solution, or the number of coating, it is possible to control the coating thickness to be finally coated.

The drying process is a process of removing the solvent and water in the slurry to dry the slurry coated on the metal current collector, and may vary depending on the solvent used. In one example, it is carried out in a vacuum oven at 50 ~ 200 ℃. As a drying method, the drying method by irradiation with warm air, hot air, low humidity wind, vacuum drying, (far) infrared rays, an electron beam, etc. are mentioned, for example. Although it does not specifically limit about drying time, Usually, it carries out in 30 second-24 hours.

After the drying process, a cooling process may be further included, and the cooling process may be slow cooling to room temperature so that the recrystallized structure of the binder is well formed.

In addition, if necessary, in order to increase the capacity density of the electrode after the drying process and to increase the adhesion between the current collector and the active materials, a pressing process may be performed in which the electrode is passed between two hot-heated rolls and compressed to a desired thickness. Can be. The said rolling process is not specifically limited in this invention, A well-known rolling process is possible. In one example, it is passed between the rotating rolls or performed using a flat plate press.

Hereinafter, with reference to the preferred embodiments of the present invention and the accompanying drawings will be described in detail the present invention. However, the present invention is not limited by the following examples, and it can be apparent to those skilled in the art that various modifications or changes can be made within the scope of the present invention.

Hereinafter, in what is referred to as 'PEO _n -lithium salt', n represents the number of moles of PEO corresponding to 1 mol of Li of the lithium salt, and X is a semi-IPN structure in what is referred to as 'PEO _n -lithium salt-X' It means crosslinked with.

Polymer electrolyte membrane manufacturing

<Manufacture example 1>

1. PEO (Mw ≒ 4,000,000) and LiFSI were mixed with acetonitrile (AN) in a molar ratio of EO: Li = 5: 1.

2. Using the solution, a 3 μm polymer electrolyte membrane and a PEO ₅ -LiFSI membrane were prepared by a solution casting method.

<Manufacture example 2>

1. Acetonitrile (AN) was mixed with PEO (Mw ≒ 4,000,000) and LiFSI in a molar ratio of EO: Li = 20: 1.

2. Using the solution, a 20 μm polymer electrolyte membrane and a PEO ₂₀ -LiFSI membrane were prepared by a solution casting method.

<Manufacture example 3>

1. Acetonitrile (AN) was mixed with PEO (Mw ≒ 4,000,000) and LiFSI in a molar ratio of EO: Li = 20: 1.

2. The solution was mixed with PEGDA (n = 10) and initiator BPO (Benzoyl peroxide) to 10 wt% of PEO ₂₀ -LiTFSI and stirred until a homogeneous solution. At this time, BPO was mixed so as to be 1 wt% of PEGDA.

3. A 20 μm polymer electrolyte membrane and a PEO ₂₀ -LiFSI-X membrane were prepared by a solution casting method using the mixed solution.

<Manufacture example 4>

1. Acetonitrile (AN) was mixed with PEO (Mw ≒ 4,000,000) and LiFSI in a molar ratio of EO: Li = 2: 1.

2. Using the solution, a 3 μm polymer electrolyte membrane and a PEO ₂ -LiFSI membrane were prepared by a solution casting method.

Production Example 5

1. Acetonitrile (AN) was mixed with PEO (Mw ≒ 4,000,000) and LiFSI in a molar ratio of EO: Li = 12: 1.

2. Using the solution, a 10 μm polymer electrolyte membrane and a PEO ₁₂ -LiFSI membrane were prepared by a solution casting method.

Ionic Conductivity Measurement

The electrolyte membranes of Preparation Example 1 and Preparation Example 2 were placed between electrodes (stainless steel and SUS), respectively, and two ion blocking electrodes were applied using an impedance analyzer (Zahner, IM6). The measurement results are shown in Table 1 below.

	Kinds	Ion Conductivity (60 ℃)
Preparation Example 1	PEO 5 -LiFSI	1.3 × 10 -4 S / cm
Preparation Example 2	PEO 20 -LiFSI	3.0 × 10 -4 S / cm

As shown in Table 1, at 60 ℃ Production Example 1 of PEO ₅ -LiFSI membrane ion conductivity of 1.3 × 10 ^-4 S / cm Production Example 2 of the ₂₀ PEO -LiFSI membrane ionic conductivity was 3.0 × 10 ^-4 S / It was found to be much lower than cm. Therefore, it was confirmed that the higher the Li content, the lower the ion conductivity, and it can be predicted that there is a problem in using the PEO ₅ -LiFSI membrane of Preparation Example 1 as a single membrane.

Lithium Simmetric Battery Manufacturing

<Example 1>

As shown in FIG. 2, a lithium symmetric cell is applied by applying the PEO ₅ -LiFSI film of Preparation Example 1 to the surface of a lithium metal and applying the PEO ₂₀ -LiFSI-X film of Preparation Example 3 therebetween. Was produced.

Comparative Example 1

As shown in FIG. 1, a lithium symmetric cell was fabricated by applying the PEO ₂₀ —LiFSI-X film of Preparation Example 3 between lithium.

All Solid Battery Manufacturing

<Example 2>

1. A positive electrode having a porosity of 10% or less and a loading of 2 mAh / cm ² was prepared by mixing LFP (LiFePO ₄ ) active material, a conductive material, and a polymer electrolyte to a size of 10.6 cm ² .

2. The first polymer electrolyte of PEO ₅ -LiFSI of Preparation Example 1 was placed on lithium.

3. The second polymer electrolyte PEO ₂₀ -LiFSI-X of Preparation Example 3 was mounted on the first polymer electrolyte.

4. The positive electrode prepared in step 1 was stacked on the second polymer electrolyte to prepare an all-solid-state battery as shown in FIG. 3 (b).

<Example 3>

1. A positive electrode having a porosity of 10% or less and a loading of 2 mAh / cm ² was prepared by mixing LFP (LiFePO ₄ ) active material, a conductive material, and a polymer electrolyte to a size of 10.6 cm ² .

2. The first polymer electrolyte of PEO ₂ -LiFSI of Preparation Example 4 was placed on lithium.

3. The second polymer electrolyte of PEO ₂₀ -LiFSI of Preparation Example 2 was mounted on the first polymer electrolyte.

4. An all-solid-state battery was manufactured by stacking the positive electrode prepared in step 1 on the second polymer electrolyte.

Comparative Example 2

1. A positive electrode having a porosity of 10% or less and a loading of 2 mAh / cm ² was prepared by mixing LFP (LiFePO ₄ ) active material, a conductive material, and a polymer electrolyte to a size of 10.6 cm ² .

2. The PEO ₂₀ -LiFSI-X film of Preparation Example 3 was placed on lithium.

3. The positive electrode prepared in step 1 was stacked to produce an all-solid-state battery as shown in FIG.

Comparative Example 3

1. A positive electrode having a porosity of 10% or less and a loading of 2 mAh / cm ² was prepared by mixing LFP (LiFePO ₄ ) active material, a conductive material, and a polymer electrolyte to a size of 10.6 cm ² .

2. The PEO ₂₀ -LiFSI second polymer electrolyte of Preparation Example 2 was placed on lithium.

3. The first polymer electrolyte of PEO ₅ -LiFSI of Preparation Example 1 was mounted on the second polymer electrolyte.

4. An all-solid-state battery was manufactured by stacking the positive electrode prepared in step 1 on the first polymer electrolyte.

<Comparative Example 4>

1. A positive electrode having a porosity of 10% or less and a loading of 2 mAh / cm ² was prepared by mixing LFP (LiFePO ₄ ) active material, a conductive material, and a polymer electrolyte to a size of 10.6 cm ² .

2. The PEO ₁₂ -LiFSI second polymer electrolyte of Preparation Example 5 was placed on lithium.

3. A second polymer electrolyte of PEO ₂₀ -LiFSI of Preparation Example 2 was mounted on the second polymer electrolyte.

4. An all-solid-state battery was manufactured by stacking the positive electrode prepared in step 1 on the second polymer electrolyte.

Interface resistance measurement

The lithium symmetric cell of Example 1 and Comparative Example 1 and the all-solid-state cells of Example 3 and Comparative Examples 3 and 4 were measured by electrochemical impedance spectroscopy (EIS) measurement. In the graphs of FIGS. 1 and 2 thus obtained, the interface resistance was confirmed at the point where the semi-circular line meets the x-axis. Interfacial resistance is shown in Table 2 below.

division	Symmetric battery		All-solid-state battery
	Example 1	Comparative Example 1	Example 3	Comparative Example 3	Comparative Example 4
Interface resistance (Ω)	130	350	200	350	2200

The resistance of the cell to which only PEO ₂₀ -LiFSI-X, which is Comparative Example 1 shown in FIG. 1, is 350 Ω, while the intermediate layer between PEO ₂₀ -LiFSI-X, which is PEO ₅ -LiFSI, which is Example 1 shown in FIG. The battery applied as an interlayer was found to have a very low resistance of about 130 Ω despite the increase in thickness of 6 μm. Therefore, it can be seen that the PEO ₅ -LiFSI film has a very low interfacial resistance with lithium.

In addition, the resistance of the all-solid-state battery in which PEO ₂ -LiFSI and PEO ₂₀ -LiFSI based on the lithium negative electrode of Example 3 were sequentially applied was 200 Ω, and Comparative Example 3, which changed the positions of the first polymer and the second polymer, was used. a negative electrode based on PEO and PEO _{5 20} -LiFSI -LiFSI was the resistance of the all-solid battery are applied sequentially appeared as 350 Ω, the second polymer only comparative example 4 of the negative electrode based on lithium PEO _{12 20} PEO -LiFSI and applying the -LiFSI The resistance of the all-solid-state battery sequentially applied was 2200 Ω. As a result, it can be seen that the interfacial resistance of the battery in which the lithium negative electrode reference first polymer electrolyte layer is disposed facing lithium and the second polymer electrolyte layer is disposed thereon is lower, and that the first polymer electrolyte layer is the first polymer electrolyte layer than the battery using only the second polymer electrolyte layer. It can be seen that the interface resistance of the battery using the polymer electrolyte layer and the second polymer electrolyte layer at the same time is lower.

Discharge capacity measurement

As shown in FIG. 4, an all-solid-state battery (Comparative Example 2, (a)) using only PEO ₂₀ -LiFSI-X has a high positive electrode loading and a high interfacial resistance with lithium, so that the discharge capacity is 130 mAh / g. It was not expressed.

However, an all-solid-state battery (Examples 2 and (b)) in which the PEO ₅ -LiFSI polymer electrolyte membrane of the present invention is applied between the lithium anode and the second polymer electrolyte PEO ₂₀ -LiFSI-X (Interlayer) is lithium. It was confirmed that the interfacial resistance with and the discharge overvoltage is reduced significantly, and sufficient discharge capacity of 155 mAh / g is implemented. Therefore, when the PEO ₅ -LiFSI polymer electrolyte membrane, which is the first polymer electrolyte, is applied to a battery, output characteristics and energy density can be improved.

Claims (11)

1. A first polymer electrolyte layer having a molar ratio of EO: Li of the polyethylene oxide polymer and the lithium salt of from 1: 1 to 7: 1; And

   A second polymer electrolyte layer having a molar ratio of EO: Li of the polyethylene oxide polymer and the lithium salt of 30: 1 to 8: 1;

   Polymer electrolyte for a solid-state battery of a multi-layer structure comprising a.
2. The method of claim 1,

   The thickness of the first polymer electrolyte layer is a polymer electrolyte for a solid-state battery of a multi-layer structure, characterized in that 1 to 5 ㎛.
3. The method of claim 1,

   The thickness of the second polymer electrolyte layer is a polymer electrolyte for a solid-state battery of a multilayer structure, characterized in that 5 to 50 ㎛.
4. The method of claim 1,

   Polymer electrolyte for a multi-layer battery, characterized in that the weight average molecular weight of the polyethylene oxide polymer is 1,000,000 to 8,000,000.
5. The method of claim 1,

   The lithium salt is LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiSCN, LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carbonate, lithium 4-phenylborate, imide And a polymer selected from a combination thereof. The polymer electrolyte for an all-solid-state battery having a multilayer structure.
6. The method of claim 1,

   The second polymer electrolyte layer is cross-linked by a crosslinkable monomer to form a semi-interpenetrating polymer network polymer electrolyte for a multi-layer battery, characterized in that.
7. The method of claim 6,

   The crosslinkable monomer comprises a-(CH ₂ -CH ₂ -O)-repeating unit, the polymer electrolyte for a solid-state battery of a multi-layer structure, characterized in that.
8. The method of claim 7, wherein

   The crosslinkable monomer is a polymer electrolyte for a solid-state battery of a multi-layer structure, characterized in that it comprises from 2 to 8 alkylene unsaturated unsaturated bonds.
9. The method of claim 6,

   The crosslinkable monomer is a polymer electrolyte for a multi-layer battery, characterized in that contained in 5 to 50 wt% with respect to the polyethylene oxide-based polymer and lithium salt.
10. In the all-solid-state battery comprising a positive electrode, a negative electrode and a solid polymer electrolyte interposed therebetween,

    The solid polymer electrolyte is an all-solid-state battery, characterized in that the polymer electrolyte of any one of claims 1 to 9.
11. The method of claim 10,

    And the first polymer electrolyte layer is disposed to face the negative electrode.

Images