KR20180036410A - All solid state battery - Google Patents

Abstract

More particularly, the present invention relates to an all solid-state battery comprising a positive electrode, a negative electrode and a sulfide-based solid electrolyte interposed therebetween, wherein the lithium-ion conductive polymer and the lithium- And a buffer layer comprising a lithium salt.
The entire solid-state cell suppresses an increase in resistance occurring at the interface between the sulfide-based solid electrolyte and the cathode due to the buffer layer, thereby realizing a high capacity battery having a stable cycle performance.

Description

All solid state battery < RTI ID = 0.0 >

The present invention relates to an all-solid-state cell capable of realizing a high-capacity battery by suppressing an increase in resistance at an interface between a cathode and a solid electrolyte.

Various batteries capable of overcoming the limitations of lithium secondary batteries at present are being studied from the viewpoints of capacity, safety, output, enlargement and miniaturization of batteries.

Typical examples are metal-air batteries with a theoretical capacity in terms of capacity as compared to lithium secondary batteries, all-solid-state batteries with no risk of explosion in terms of safety, and super- (supercapacitor), NaS cell or RFB (redox flow battery) in the aspect of enlargement, and thin film battery in the aspect of miniaturization have been continuously studied in academia and industry.

All solid-state batteries refer to a battery in which a liquid electrolyte used in a lithium secondary battery has been replaced with a solid. Since no flammable solvent is used in the battery, no ignition or explosion occurs due to the decomposition reaction of the conventional electrolyte solution. Can be greatly improved. In addition, since Li metal or Li alloy can be used as a negative electrode material, energy density with respect to the mass and volume of the battery can be remarkably improved.

The solid electrolyte may be a polymer solid electrolyte such as a polystyrene-polyethylene oxide block copolymer, a crystalline solid electrolyte such as LLT (Li0.35La0.55TiO3), a silica-based amorphous solid electrolyte, a sulfide system such as thio-LISICON Solid electrolytes and the like. Among them, sulfide-based solid electrolytes are attracting attention due to their high ion conductivity.

Since the solid electrolyte is a solid phase in which the electrolyte is not liquid, the interface between the electrode and the solid electrolyte is very important. That is, when a failure occurs at the interface or when the amount of interfacial contact is insufficient, the characteristics of the battery greatly deteriorate, and control thereof is important.

Therefore, efforts have been made to improve the interfacial characteristics through structural changes in which the compositions of the solid electrolytes are changed or laminated in a multilayer structure.

Korean Patent Laid-Open Publication No. 2015-0018559 proposes a pre-solid battery having a second solid electrolyte layer including a mixture of a first solid electrolyte layer / a sulfide solid electrolyte and a binder composed of a sulfide solid electrolyte powder. This patent mentions that the formation of a two-layered electrolyte layer can further improve lithium ion conductivity and prevent battery shorting, thereby improving battery characteristics.

However, in the case of the all solid electrolyte having the electrolyte of the multi-layered structure, the thickness of the electrode became thick and a high resistance layer of Li ₂ S was formed at the interface with the lithium metal used as a cathode when the sulfide-based solid electrolyte was repeatedly charged and discharged. In addition, unstable interfacial properties such as a metal element contained in the sulfide-based solid electrolyte precipitated at the interface with the electrode were observed.

Furthermore, the deterioration of the battery characteristics with respect to the formation of lithium dendrite due to the use of the lithium electrode occurred more seriously. When a sulfide-based solid electrolyte is used, graphite is generally used as a negative electrode. However, use of the graphite has a limitation in implementation of a high capacity battery.

Korean Patent Laid-Open Publication No. 2015-0018559 (Feb. 22, 2013), a whole solid battery and a manufacturing method thereof

In order to solve the above-described problems, the present inventors have found that a buffer layer is formed at the interface between a solid electrolyte and a cathode to maintain a stable interface state, thereby suppressing an increase in resistance at the interface and to provide a lithium electrode and a sulfide-based solid electrolyte It is possible to realize a high capacity battery, and thus the present invention has been completed.

Accordingly, an object of the present invention is to provide a pre-solid battery in which a buffer layer is formed at an interface between a cathode and a solid electrolyte.

In order to achieve the above object, the present invention provides an all solid-state battery comprising a positive electrode, a negative electrode, and a sulfide-based solid electrolyte interposed therebetween,

And a buffer layer comprising a lithium ion conductive polymer and a lithium salt between the cathode and the sulfide-based solid electrolyte.

The lithium ion conductive polymer may be polyethylene oxide, polypropylene oxide, polyacrylonitrile. And at least one member selected from the group consisting of polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluorophosphate, polyvinyl acetate, polyethyleneimine, and polyethylene sulfide.

The lithium salt is typically LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiSCN, Li (FSO ₂ ) ₂ N, LiCF ₃ CO _{2, LiCH 3 SO 3, LiCF} 3 SO 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiC 4 F 9 SO 3, LiC (CF 3 SO 2) 3, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, and 4-phenylborate lithium imide.

According to the present invention, a buffer layer positioned between a cathode and a sulfide-based solid electrolyte suppresses an increase in resistance occurring at these interfaces, thereby making it possible to produce a cell having a stable cycle performance.

Such a pre-solid battery enables lithium metal to be used as a cathode, thereby enabling a high capacity battery to be realized.

1 is a cross-sectional view showing a pre-solid battery according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a pre-solid battery according to the present invention, showing (a) before charging, and (b) after charging.
3 is a cross-sectional view illustrating a pre-solid battery according to a second embodiment of the present invention.
4 is a cross-sectional view illustrating a pre-solid battery according to a third embodiment of the present invention.

The entire solid-state cell according to the present invention is designed to improve the characteristics of the cell by controlling the interface characteristics between the electrode, particularly the anode and the sulfide-based solid electrolyte, so that the interface resistance between the anode and the sulfide- It contains a new layer.

FIG. 1 is a cross-sectional view showing a pre-solid battery 10 according to the present invention. The pre-solid battery 10 is composed of a cathode 11, a solid electrolyte 13 and a cathode 15, A buffer layer 17 is formed between the solid electrolyte 13 and the solid electrolyte 13.

The buffer layer 17 is used for solving the problem that the sulfide solid electrolyte material reacts at the interface with the lithium metal and a high resistance layer is formed at the interface between the sulfide solid electrolyte material and the interface resistance. At this time, when the lithium metal is used for the cathode 11 due to the introduction of the buffer layer 17, an increase in the interface resistance between the lithium metal and the sulfide-based solid electrolyte 13 is suppressed. At this time, the suppression of the increase in resistance at the interface can be achieved by increasing the ion conductivity.

In order to enhance the ion conductivity, the buffer layer 17 is formed by including a lithium ion conductive polymer and a lithium salt.

The lithium ion conductive polymer is not particularly limited in the present invention, but may be polyethylene oxide, polypropylene oxide, polyacrylonitrile. It is possible to use one species selected from the group consisting of polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluorophosphate, polyvinyl acetate, polyethyleneimine, and polyethylene sulfide, preferably polyethylene oxide do.

The lithium ion conductive polymer has a weight average molecular weight of 10,000 to 5,000,000 g / mol. If the molecular weight is less than the above range, the polymer protective film may be weak in strength and may be dissolved in contact with the electrolyte. On the other hand, if the molecular weight exceeds the above range, migration of lithium ions may be suppressed to deteriorate the performance of the battery. use.

The lithium salt is used to increase the lithium ion conductivity of the lithium ion conductive polymer. Through the use of the lithium salt, the buffer layer 17 does not act as a resistance layer and overpotential does not occur during charging and discharging, do.

LiBCl ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiBF ₆ , LiBF ₄ , LiBF ₆ , LiBF ₄ , LiBF ₆ , _{LiAsF 6, LiSbF 6, LiAlCl 4} , LiSCN, Li (FSO 2) 2 N (Lithium bis (fluorosulfonyl) imide, hereinafter referred to as _{'LiFSI') LiCF 3 CO 2} , LiCH 3 SO 3, LiCF 3 SO 3, LiN ( SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, Lithium perchlorate, lithium peroxide, lithium 4-phenylborate, and a combination thereof. Preferably, LiFSI is used. The ionic conductivity of the lithium salt varies depending on the kind thereof. The ion mobility can be strengthened or weakened due to the interaction between the lithium ion and the polymer chain. When PEO and LiFSI are used together, the optimum effect is obtained .

The concentration of such a lithium salt is not particularly limited in the present invention, and it can be used in a wide range from a low concentration to a high concentration such as a concentration of 0.1 to 10M.

The buffer layer 17 according to the present invention physically inhibits the growth of lithium dendrite due to the use of the lithium ion conductive polymer, together with the effect of suppressing the increase in the interfacial resistance due to the increase in the lithium ion conductivity.

When lithium metal is used as the cathode 11, electrons moving to the lithium foil through the current collector move in a single direction flow when the battery is driven. This causes non-uniformity of the electron density on the lithium surface, and thus lithium dendrite can be formed. Such lithium dendrites may ultimately cause damage to the solid electrolyte 13 and may cause short-circuiting of the pre-solid battery 10.

The buffer layer 17 reduces the direct contact between the cathode 11 and the solid electrolyte 13 to physically suppress the growth of the lithium dendrite. At this time, the higher the strength of the buffer layer 17, the more physically the generation of lithium dendrite on the surface can be suppressed. However, the buffer layer 17 becomes harder and fragile than the case of using too high a strength, The buffer layer 17 may be damaged by the volume change of the buffer layer 17. Therefore, in the present invention, the above-mentioned lithium ion conductive polymer having flexibility is used.

The thickness of the buffer layer 17 is not limited to the present invention. The thickness of the buffer layer 17 is within a range not securing the internal resistance of the battery while securing the above effect, for example, 1 to 10 탆. If the thickness is less than the above range, the function as the buffer layer 17 can not be performed. On the contrary, if the thickness exceeds the above range, stable interface characteristics can be provided, but the initial interface resistance is increased, .

The buffer layer is a lithium ion conductivity of 1 × 10 ^-5 S / cm or more is preferred, if the lithium ion conductivity is too low may act as a resistance layer, such as Li ₂ S, Li-ion conductive polymer and a lithium salt type and concentration And so on to control the lithium ion conductivity.

The production of the buffer layer 17 is not particularly limited in the present invention. For example, the buffer layer 17 may be prepared by adding a lithium salt, PEO, and an initiator in a solvent, followed by coating and drying.

Any solvent may be used as long as it can dissolve the lithium salt and PEO, preferably a non-aqueous organic solvent. The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move, and known carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvents can be used. Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, -Dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, 4-methyl- The organic solvent may be selected from the group consisting of diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, An aprotic organic solvent such as dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl pyrophosphate, and ethyl propionate may be used.

The coating may be a method used in conventional wet processes such as spin coating, spray coating, doctor blade coating, dip coating and the like. However, it may be preferable to perform spin coating for uniformity of the coating and ease of control of the coating thickness.

After the coating, drying is performed. The drying can be appropriately selected at a temperature higher than the boiling point of the solvent and at a temperature lower than the Tg of the polymeric material of the protective layer. The solvent remaining on the surface of the lithium can be removed through the drying process and the adhesion of the polymer protective film can be improved.

The buffer layer 17 may be formed directly on the electrode or formed on a separate substrate, and then transferred onto the electrode.

The entire solid battery 10 proposed in the present invention defines the structure of the solid electrolyte as described above, and the other components constituting the solid electrolyte 10, namely, the anode 15 and the cathode 11 are not particularly limited to the present invention, Follow the instructions.

The cathode (11) of the pre-solid electrolyte (10) is made of lithium metal alone or a lithium metal laminated on the anode current collector.

Particularly, in the pre-solid battery 10 according to the present invention, lithium metal can be used as the cathode 11 even if a sulfide-based solid electrolyte is used as the solid electrolyte 13 due to the presence of the buffer layer 17. [

In this case, the negative electrode active material may be a lithium metal or a lithium alloy. The lithium alloy may be an alloy of lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn.

 The anode current collector is not particularly limited as long as it has electrical conductivity without causing any chemical change in the whole solid battery. For example, the anode current collector may be formed on the surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, Carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. The negative electrode current collector may be formed in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, and the like having fine irregularities on its surface.

The anode (15) of the pre-solid battery (10) according to the present invention is not particularly limited and may be a material used for a known pre-solid battery (10).

The electrode is a positive electrode collector when the electrode is the anode 15, and is a negative electrode collector when the electrode is a cathode.

The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, carbon, nickel , Titanium, silver, or the like may be used.

The positive electrode active material may vary according to the application of the all-solid battery _{(10), LiNi 0.8-x} Co 0.2 AlxO 2, LiCo x Mn y O 2, LiNi x Co y O 2, LiNi x Mn y O 2, LiNi x Co lithium transition metal oxides such as _y Mn _z O ₂ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ and Li ₄ Ti ₅ O ₁₂ ; Cu ₂ Mo ₆ S ₈ , chalcogenides such as FeS, CoS and MiS, oxides, sulfides or halides of scandium, ruthenium, titanium, vanadium, molybdenum, chromium, manganese, iron, cobalt, nickel, And more specifically TiS ₂ , ZrS ₂ , RuO ₂ , Co ₃ O ₄ , Mo ₆ S ₈ , V ₂ O ₅ and the like may be used, but the present invention is not limited thereto.

The shape of the cathode active material is not particularly limited and may be a particle shape, for example, a spherical shape, an elliptical shape, a rectangular parallelepiped shape, or the like. The average particle diameter of the cathode active material may be within the range of 1 to 50 占 퐉, but is not limited thereto. The average particle diameter of the cathode active material can be obtained, for example, by measuring the particle size of the active material observed by a scanning electron microscope and calculating the average value thereof.

The binder contained in the anode 15 is not particularly limited, and a fluorine-containing binder such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) may be used.

The content of the binder is not particularly limited as long as it can fix the cathode active material, and may be in the range of 0 to 10 wt% with respect to the entire anode 15.

The anode 15 may further include a conductive material. The conductive material is not particularly limited as long as it can improve the conductivity of the anode 15, and examples thereof include nickel powder, cobalt oxide, titanium oxide, and carbon. Examples of the carbon include any one selected from the group consisting of Ketjen black, acetylene black, furnace black, graphite, carbon fiber and fullerene, or at least one of them.

At this time, the content of the conductive material may be selected in consideration of the conditions of other cells such as the kind of the conductive material, and may be, for example, in the range of 1 to 10 wt%

Further, the solid electrolyte 13 of the pre-solid battery 10 according to the present invention can be a sulfide-based solid electrolyte 13.

The solid electrolyte 13 of the pre-solid battery may be any solid electrolyte having a high ion conductivity (10 ^-3 S / cm) and excellent electrochemical stability. Among them, the solid electrolyte 13 may be a sulfide-based solid electrolyte 13 have. The ionic conductivity of the solid electrolyte is 10 ^-2 S / cm), and the ion conductivity is close to that of the organic electrolyte.

The sulfide-based solid electrolyte 13 has a problem in that the interface resistance with the electrode is high. However, this problem can be solved by the presence of the buffer layer 17 as described above.

The sulfide-based solid electrolytes 13 which can be used are not particularly limited in the present invention, and all the known sulfide-based solid electrolytes 13 may be used.

Specifically, the sulfide-based solid electrolyte 13 may include at least one of Li ₂ S, Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , SiS ₂ , Al ₂ S ₃ , B ₂ S ₃ , GeS ₂ , P ₂ S ₃ , P _{2 S 5, as 2 S 3} , Sb 2 S 3 , and includes at least one sulfur compound selected from the group consisting of Li ₂ SO _4, here in _{LiF, LiPF 6, LiBF 4,} LiSbF 6, LiAsF 6, LiCF 3 SO ₃ , LiN (CF ₃ SO ₂ ) ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ and LiN (CxF _{2x + 1} SO ₂ ) (C _x F _{2y + 1} SO ₂ ) x and y are natural numbers) at least one member selected from the group lithium consisting of fluorine compounds, or _{LiI, Li 3 PO 4, Li} 4 SiO 4, Li 4 GeO 4, Li 3 BO 3, Li 3 AlO 3, LiCl, LiBr , Li ₂ O, Li ₃ BO ₃ I, Li ₂ CO ₃ and Li ₃ N, and the like.

For _{example, Li 2 SP 2 S 5,} Li 2 SB 2 S3, Li 2 S-Si 2 S 3, Li 2 S-SiS 2, LiI-Li 2 SB 2 S 3, LiI-Li 2 S-SiS 2, Li ₂ SP ₂ S ₅ -Li ₄ SiO, Li ₂ S-Ga ₂ S ₃ -GeS ₂ and Li ₂ S-Sb ₂ S ₃ -GeS ₂ , Li ₁₁ Si ₂ PS ₁₂ , Li ₁₀ SnP ₂ S ₁₂ , Li _2.2 Zn _0.1 Zr _1.9 S ₃ , and the like. For example, a thio- (lithium super ionic conductor) solid electrolyte represented by the following Table 1 can be used.

compound material Ion conductivity Li ₂ SP ₂ S ₅ 80Lis ₂ -20P ₂ S ₅ 3.2 x 10 ^-3 S · cm ^-1 70Li ₂ S-20P ₂ S ₆ 2.1 × 10 ^-3 S · cm ^-1 Li ₂ SP ₂ S ₅ -Li I 10 ^-3 S · cm ^-1 Li ₂ SP ₂ S ₅ Glass ceramic 32 × 10 ^-3 S · cm ^-1 LiI-Li ₂ SP ₂ S5-P ₂ O ₅ 1 × 10 ^-7 S · cm ^-1 Li ₂ S-SiS ₂ Li ₂ S-SiS ₂ 2 × 10 ^-3 S · cm ^-1 0.6Li ₂ S-0.4SiS ₂ 8 × 10 ^-3 S · cm ^-1 (30% LiI doped) Li ₂ S-SiS ₂ -Li ₃ PO ₄ 7.6 × 10 ^-4 S · cm ^-1 0.97 [0.6Li ₂ S-0.4SiS ₂ ] -0.03 Li ₄ SiO ₄ 1.5 × 10 ^-3 S · cm ^-1 Li ₂ S-SiS ₂ -LiSiO ₄ 1.1 × 10 ^-4 S · cm ^-1 Li ₂ -SiS ₂ -Li _x Mo _y 1.1 × 10 ^-3 S · cm ^-1 (M = Si, p)
7 × 10 ^-3 S · cm ^-1 (M = Ge) Li _3.4 Si _0.4 P _0.6 S ₄ 6.4 × 10 ^-4 S · cm ^-1 Li ₂ S-GeS ₂ Li ₂ -GeS ₂ -Li I 10 ^-5 S · cm ^-1 Li ₄ GeS ₄ 10 ^-3 S · cm ^-1 Li _3.35 Ge _0.35 P _0.65 S ₄ 2.39 × 10 ^-3 S · cm ^-1 95Li ₃ PS ₄ · 5Li ₄ GeS ₄ 9.9 × 10 ^-3 S · cm ^-1 Li _4-x Ge _1-x P _x S ₄ 10 ^-3 S · cm ^-1 Li ₃ PS ₄ 1.5 × 10 ^-4 S · cm ^-1 Li ₄ SiPS ₄ 6.4 × 10 ^-4 S · cm ^-1 Li ₄ GePS ₄ 2.2 x 10 ^-3

The sulfide-based solid electrolyte 13 can be either crystalline or amorphous, and is not particularly limited in the present invention. Also, although the shape is not particularly limited, it is preferable that the average particle diameter is within the range of 0.1 μm to 50 μm.

The thickness of the sulfide-based solid electrolyte layer 13 greatly differs depending on the structure of the pre-solid battery 10. However, for example, it is preferably 0.1 m or more and 1 mm or less, and more preferably 1 m or more and 100 m or less. It is preferable that such a solid electrolyte 13 has a high lithium ion conductivity.

 The production of the all-solid-state cell 10 having the above-described structure is not particularly limited in the present invention, and can be manufactured by a known method.

For example, the solid electrolyte 13 is disposed between the anode 15 and the cathode 11, and the cell is assembled by compression molding.

At this time, the buffer layer 17 may be formed on the cathode 11 or may be formed on the solid electrolyte 13 and assembled. Alternatively, the buffer layer 17 may be prepared separately, and then the cathode 11 may be disposed between the cathode 11 and the solid electrolyte 13 to assemble the cells.

The assembled cell is installed in the casing and then sealed by heat compression or the like. Laminate packs made of aluminum, stainless steel or the like, and cylindrical or square metal containers are very suitable for the exterior material.

The entire solid battery 10 proposed in the present invention can operate safely even if lithium metal is used for the cathode 11 and the sulfide-based solid electrolyte 13 is used for the solid electrolyte 13, ) Can be implemented.

For example, portable devices such as mobile phones, notebook computers, and digital cameras, power tools; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Changes and modifications may fall within the scope of the appended claims.

[Example]

Example 1: Preparation of Whole Solid Battery (Half-cell)

Polyethylene oxide (PEO) and LiTFSI lithium salt were added to the solvent at a ratio of ethylene oxide (EO) / Li = 9 to prepare a coating solution for forming a buffer layer. The coating solution was coated on lithium metal (150 mu m) as a negative electrode and dried to form a 20 mu m buffer layer.

The Li electrode where the buffer layer was formed was called Li ₁₀ SnP ₂ S ₁₂ Li-Li symmetric cell was fabricated on both sides of the solid electrolyte layer made of 300 mg. A lithium counter electrode was used to strike at a size of? 14, and then pressed at 100 MPa to prepare a coin-type half cell.

Comparative Example 1: Preparation of all solid batteries

A coin-type Li-Li symmetric cell was prepared in the same manner as in Example 1, except that a buffer layer was not formed.

Experimental Example 1: Evaluation of interfacial resistance characteristics

Using the cells of Example 1 and Comparative Example 1, the change of the interface resistance between the negative electrode and the solid electrolyte was measured according to the application of the buffer layer.

FIG. 2 is a graph showing the interfacial resistance of the battery manufactured in Comparative Example 1, showing that the interfacial resistance rapidly increased after 24 hours of battery operation.

FIG. 3 is a graph showing resistance changes with time in Example 1 and Comparative Example 1. FIG. Referring to FIG. 3, when the buffer layer is absent as in Comparative Example 1, the interface resistance increases proportionally with time, whereas when the buffer layer is applied as in Embodiment 1, the interface resistance hardly increases .

Example 2: Preparation of full solid cell (full-cell)

The positive electrode composite powder was prepared by adding 3 g of active material TiS ₂ and solid electrolyte Li ₁₀ SnP ₂ S ₁₂ at a weight ratio of 1: 2 to the mortar and hand mixing for 5 minutes.

A solid electrolyte layer was formed by applying 300 mg of Li ₁₀ SnP ₂ S ₁₂ as a solid electrolyte to a mold having a diameter of Φ 16 mm and applying it at a pressure of 400 MPa.

Then, the long axis of the mold mold was drawn out, and 0.025 g of the prepared mixed powder was put on one side of the solid electrolyte layer, and the positive electrode layer was prepared by applying a pressure of 400 MPa at 25 캜 in a hydraulic press machine.

Ethylene oxide (EO) / Li = 9 in a solvent. The coating solution was coated on a negative electrode lithium metal (150 mu m) and dried to form a buffer layer having a thickness of 10 mu m.

Then, an Li foil having the buffer layer formed thereon was put on the opposite surface (the portion where the short axis of the mold mold reached) on which the anode was formed, and pressed at a pressure of 100 MPa for 10 seconds.

The completed pellet (cell structure) was taken out and placed in a coin cell and assembled to complete the cell.

Experimental Example 2: Evaluation of cell characteristics

Charging and discharging of all solid-state batteries were performed at 60 ° C in the range of 1.5V to 3.0V at 0.1C, and the results obtained are shown in FIG.

FIG. 4 shows the battery characteristics of the all-solid battery prepared in Example 2, showing that the capacity was maintained at 87% up to the 66th cycle, and the battery production showing excellent characteristics in terms of initial capacity and cycle performance It is possible to know.

The pre-solid battery according to the present invention can be applied as a high capacity high output battery in various technical fields.

10: all solid state batteries 11: cathode
13: solid electrolyte 15: anode
17: buffer layer

Claims (8)

In an all-solid-state cell having an anode, a cathode, and a sulfide-based solid electrolyte interposed therebetween,
And a buffer layer comprising a lithium ion conductive polymer and a lithium salt between the cathode and the sulfide-based solid electrolyte. The method according to claim 1,
The lithium ion conductive polymer may be at least one selected from the group consisting of polyethylene oxide, polypropylene oxide, polyacrylonitrile. Wherein the polymer electrolyte is at least one selected from the group consisting of polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluorophosphate, polyvinyl acetate, polyethyleneimine, and polyethylene sulfide. The method according to claim 1,
Wherein the lithium ion conductive polymer has a weight average molecular weight of 10,000 to 5,000,000 g / mol. The method according to 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 carboxylate lithium, And at least one member selected from the group consisting of iron and iron. The method according to claim 1,
Wherein the buffer layer has a thickness of 1 to 10 mu m. The method according to claim 1,
Wherein the buffer layer has a lithium ion conductivity of 1 x 10 < ^-5 > S / cm or more. The method according to claim 1,
Wherein the negative electrode comprises lithium metal or a lithium alloy composed of lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, A pre-solid state battery. The method according to claim 1,
The sulfide-based solid electrolyte may be selected from the group consisting of Li ₂ S, Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , SiS ₂ , Al ₂ S ₃ , B ₂ S ₃ , GeS ₂ , P ₂ S ₃ , P ₂ S ₅ , As ₂ S ₃ , Sb ₂ S ₃ , and Li ₂ SO ₄ .

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