KR101796749B1 - Ceramic composite electrolyte, method for manufacturing the same, and lithium secondary battery including the same - Google Patents

Abstract

The present invention relates to a ceramic composite electrolyte, a method for producing the same, and a lithium secondary battery comprising the ceramic composite electrolyte. And a heat resistant polymer, wherein the ionic liquid comprises a solvent and a lithium salt, and the ionic liquid is a solid electrolyte membrane comprising a solid electrolyte membrane By weight of the solid electrolyte membrane and not more than 95% by weight of the solid electrolyte membrane based on 100% by weight of the total amount of the ceramic composite electrolyte; And the ionic liquid is contained in an amount of 5 wt% or more and 35 wt% or less, a process for producing the same, and a lithium secondary battery comprising the electrolyte.

Description

TECHNICAL FIELD [0001] The present invention relates to a ceramic composite electrolyte, a method for producing the same, and a lithium secondary battery including the same. BACKGROUND ART [0002]

Ceramic composite electrolyte, a method for producing the same, and a lithium secondary battery comprising the same.

Since existing lithium secondary batteries basically use liquid electrolytes, safety problems against explosion and ignition are constantly occurring, and many researches have been conducted to solve them, but there are still ways to solve them fundamentally I can not. In addition, such a liquid electrolyte has a disadvantage that a high voltage anode can not be used because the potential window is low.

One of the most popular methods of solving this problem is to convert the organic electrolyte corresponding to the fuel into a solid electrolyte so that the explosion / ignition as described above does not occur fundamentally.

Typical solid electrolytes include ceramic solid electrolytes. Ceramic solid electrolytes include LIPON, NASICON, sulfide-based, and oxide-based solid electrolytes. When such a ceramic solid electrolyte is applied to a lithium secondary battery, the thermal stability and the electrochemical stability can be improved.

However, the ceramic solid electrolyte has a problem of low electrochemical characteristics because of high interfacial resistance between the ceramic particles in the solid electrolyte or between the solid electrolyte and the electrode.

Therefore, a new approach is needed to solve the problem of interface resistance of a ceramic solid electrolyte with excellent thermal and electrochemical stability.

One embodiment of the present invention provides a ceramic composite electrolyte capable of reducing the above-mentioned interfacial resistance and improving the thermal stability and electrochemical characteristics of the lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same I want to.

One embodiment of the present invention relates to a ceramic particle; And a heat resistant polymer, wherein the ionic liquid comprises a solvent and a lithium salt, and the ionic liquid is a solid electrolyte membrane comprising a solid electrolyte membrane By weight of the solid electrolyte membrane and not more than 95% by weight of the solid electrolyte membrane based on 100% by weight of the total amount of the ceramic composite electrolyte; Wherein the ionic liquid is contained in an amount of 5 wt% or more and 35 wt% or less.

Wherein the solid electrolyte membrane is formed by forming an interconnected porous network in which the heat resistant polymer is three-dimensionally irregularly and continuously connected to each other by the heat-resistant polymer, and the ceramic particles in the interconnected pore structure are positioned .

The reason why the ionic liquid is impregnated into the pores in the solid electrolyte membrane is that the ionic liquid is contained in pores between different ceramic particles in the solid electrolyte membrane, between the ceramic particles and the polymer, and / It may be impregnated.

Wherein the ionic liquid comprises at least 50% by weight and at most 95% by weight of solvent, based on 100% by weight of the total ionic liquid; 5% by weight or more, and 50% by weight or less of a lithium salt.

The weight ratio (ceramic particle / heat resistant polymer) of the ceramic particles to the heat resistant polymer in the solid electrolyte membrane may be 2/1 or more and 5/1 or less.

The heat resistant polymer may be at least one selected from the group consisting of polyurethane (PU), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), polyethylene oxide Polypropylene oxide (PPO), or a combination thereof.

The ceramic particles may be selected from the group consisting of garnet-type oxides, TiO ₂ , Al ₂ O ₃ , BaTiO ₃ , SiO ₂ , perovskite-type oxides, LISICON, LiPON, NASICON), a glass-ceramic solid electrolyte, or a combination thereof.

The solvent may be Py ₁₄ TFSI, Py ₁₃ TFSI, EMITFSI, BMITFSI, or a combination thereof.

The lithium salt may be LiPF ₆ , LiClO ₄ , LiTFSI, or a combination thereof.

The ceramic composite electrolyte may have a viscosity of 1000 cP or more and 200000 cP or less.

Another embodiment of the present invention is a ceramic particle comprising ceramic particles; And a heat-resistant polymer; And a step of impregnating the solid electrolyte membrane with an ionic liquid, wherein the ionic liquid comprises a solvent and a lithium salt, wherein the total amount of the ceramic composite electrolyte is 100 wt% , At least 65 wt% and at most 95 wt% of the solid electrolyte membrane; Wherein the ionic liquid is contained in an amount of 5 wt% or more and 35 wt% or less.

Impregnating the solid electrolyte membrane with an ionic liquid, wherein the ionic liquid is impregnated with pores between different ceramic particles in the solid electrolyte membrane, between the ceramic particles and the polymer, or between different polymers .

The ceramic particles; And the heat-resistant polymer, the weight ratio of the ceramic particles to the heat-resistant polymer (ceramic particle / heat-resistant polymer) may be 2/1 or more and 5/1 or less.

Wherein the ionic liquid comprises at least 50% by weight and at most 95% by weight of solvent, based on 100% by weight of the total ionic liquid; 5% by weight or more, and 50% by weight or less of a lithium salt.

The ionic liquid may be prepared by stirring a mixture of the solvent and the lithium salt at a rate of 100 rpm or more and 500 rpm or less.

The ionic liquid may be prepared by stirring a mixture of the solvent and the lithium salt for 6 hours or more and 24 hours or less.

The ionic liquid may be prepared by stirring a mixture of the solvent and the lithium salt at a temperature of 60 占 폚 or higher and 120 占 폚 or lower.

Impregnating the solid electrolyte membrane with an ionic liquid may be performed in an argon (Ar) atmosphere.

The heat resistant polymer may be at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide , Polyurethane (PU), or a combination thereof.

The ceramic particles may be selected from the group consisting of TiO ₂ , Al ₂ O ₃ , BaTiO ₃ , SiO ₂ , perovskite-type oxide, LISICON, NASICON garnet-type oxide, Glass-ceramic solid electrolyte, or a combination thereof.

The solvent may be Py ₁₄ TFSI, Py ₁₃ TFSI, EMITFSI, BMITFSI, or a combination thereof.

The lithium salt may be LiPF ₆ , LiClO ₄ , LiTFSI, or a combination thereof.

According to another embodiment of the present invention, there is provided a ceramic composite electrolyte according to one embodiment of the present invention. anode; And a negative electrode.

One embodiment of the present invention relates to a ceramic composite electrolyte capable of reducing interfacial resistance generated in a ceramic solid electrolyte and further improving thermal stability and electrochemical characteristics of the lithium secondary battery, a method for producing the same, Thereby providing a secondary battery.

1 is a scanning electron microscope (SEM) photograph (below) of the ceramic composite electrolyte prepared in Example 1 of the present invention, and a scanning electron microscope photograph (above) of a solid electrolyte membrane before the ionic liquid is impregnated .
Fig. 2 shows ion conductivity measurement data for each of the electrolytes of Example 1 and Comparative Example 1 of the present invention.
Fig. 3 shows thermal stability evaluation data for each of the electrolytes of Example 1 and Comparative Example 1 of the present invention.
4 is initial charge / discharge evaluation data of each of the coin cells of Example 2 and Example 2 of the present invention.
5 is data for evaluating the life characteristics of coin cells according to the second and the second embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

One embodiment of the present invention relates to a ceramic particle; And a heat resistant polymer, wherein the ionic liquid comprises a solvent and a lithium salt, and the ionic liquid is a solid electrolyte membrane comprising a solid electrolyte membrane By weight of the solid electrolyte membrane and not more than 95% by weight of the solid electrolyte membrane based on 100% by weight of the total amount of the ceramic composite electrolyte; Wherein the ionic liquid is contained in an amount of 5 wt% or more and 35 wt% or less.

The ceramic solid electrolyte generally proposed has a problem of low electrochemical characteristics due to high interfacial resistance between the ceramic particles in the solid electrolyte or between the solid electrolyte and the electrode.

However, in one embodiment of the present invention, an electrolyte having excellent thermal and electrochemical characteristics can be obtained by mixing a ceramic particle, a heat-resistant polymer, and an ionic liquid to prepare a composite electrolyte. Further, the ionic liquid cell on the surface of the ceramic and the heat-resistant polymer can reduce the high interface resistance of the ceramic particles, thereby maximizing the electrochemical characteristics of the lithium secondary battery.

The ceramic composite electrolyte includes ceramic particles; And the heat-resistant polymer is contained in an amount of 65 wt% or more and 95 wt% or less based on 100 wt% of the total amount of the ceramic composite electrolyte; . If the content of the solid electrolyte membrane is too small, there may arise a problem of deterioration of the ceramic properties in the composite electrolyte. If the content of the solid electrolyte membrane is too large, the lithium ion conductivity of the composite electrolyte may be lowered due to the interface resistance of the ceramic.

The ionic liquid added to reduce the interfacial resistance between the ceramic particles or between the composite electrolyte and the electrode may be contained in an amount of 5 wt% or more and 35 wt% or less based on 100 wt% of the total amount of the ceramic composite electrolyte have. However, when the ionic liquid is contained too much, there is a possibility that the liquid leaks from the ceramic composite electrolyte. If the ionic liquid is contained in too small amount, the liquid may not sufficiently penetrate into the void space between the ceramic particles, and lithium ion conductivity may be reduced.

Wherein the solid electrolyte membrane is formed by forming an interconnected porous network in which the heat resistant polymer is three-dimensionally irregularly and continuously connected to each other by the heat-resistant polymer, and the ceramic particles in the interconnected pore structure are positioned .

The reason why the ionic liquid is impregnated into the pores in the solid electrolyte membrane is that the ionic liquid is present between the different ceramic particles in the solid electrolyte membrane, between the ceramic particles and the polymer, and / It may be impregnated with pore. Further, the ionic liquid is a liquid at room temperature, and has excellent ionic conductivity, thermal stability, and electrochemical stability, thereby contributing to improvement in battery characteristics.

1 is a scanning electron microscope (SEM) photograph (below) of the ceramic composite electrolyte prepared in Example 1 of the present invention, and a scanning electron microscope photograph (above) of a solid electrolyte membrane before the ionic liquid is impregnated . As can be seen from Fig. 1, it can be seen that the ionic liquid is impregnated between the different ceramic particles present in the solid electrolyte membrane, between the ceramic particles and the polymer, and / or between the different polymers.

By impregnating the ionic liquid in the above-described manner, the ionic liquid cell is formed on the surfaces of the ceramic particles and the polymer, so that the interfacial resistance between the ceramic particles and between the composite electrolyte and the electrode can be reduced.

Wherein the ionic liquid comprises at least 50% by weight and at most 95% by weight of solvent, based on 100% by weight of the total ionic liquid; 5% by weight or more, and 50% by weight or less of a lithium salt.

Here, the solvent may be Py ₁₄ TFSI, Py ₁₃ TFSI, EMITFSI, BMITFSI, or a combination thereof. In the lithium ion conduction, it is more effective to reduce the conduction of ions other than the migration of Li + cations. TFSI ^- anions have a higher molecular weight than PF ₆ - anions used in common liquid electrolytes, It can play a role of helping the evangelism.

The lithium salt may be LiPF ₆ , LiClO ₄ , LiTFSI, or a combination thereof. However, the present invention is not limited thereto, and other commonly used lithium salts may be used.

If the content of the solvent is too large, there is a problem that the liquid is leaked from the ceramic composite electrolyte. On the other hand, if the amount of the solvent is too small, the liquid can not sufficiently penetrate into the void space between the ceramic particles, and the lithium ion conductivity may be decreased, and incomplete dissolution may occur.

The heat resistant polymer may be at least one selected from the group consisting of polyurethane (PU), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), polyethylene oxide Polypropylene oxide (PPO), or a combination thereof. Such a heat-resistant polymer may be added to the solid electrolyte membrane to contribute to the composite electrolyte having high stretchability and high resistance. In particular, polyurethane (PU) It has excellent electrochemical stability and is used as a binder for high-voltage anode. It is used as a composite electrolyte for high flexibility and high potential window, because it has excellent elasticity and is used as rubber and has a lower electrochemical stability (potential window) than conventional polymers. Can be obtained.

The ceramic particles may be selected from the group consisting of garnet-type oxides, TiO ₂ , Al ₂ O ₃ , BaTiO ₃ , SiO ₂ , perovskite-type oxides, LISICON, LiPON, NASICON), a glass-ceramic solid electrolyte, or a combination thereof.

More specifically, the garnet type oxide may be represented by the following general formula (1).

[Chemical Formula 1]

Li _(7-x) M ¹ _x La ₃ Zr _{2 -w} M ² _w O ₁₂

M ¹ is selected from the group consisting of Al, Na, K, Rb, Cs, Fr, Mg, Ca, and combinations thereof, and may be specifically Al. In addition, M ² may be selected from the group consisting of Ta, B, Nb, Sb, Sn, Hf, Bi, W, Se, Ga, Ge and combinations thereof. Further, 0? X? 1.5 and 0? W <0.15.

The weight ratio (ceramic particle / heat resistant polymer) of the ceramic particles to the heat resistant polymer in the solid electrolyte membrane may be 2/1 or more and 5/1 or less. If the content of ceramic particles in the solid electrolyte membrane is too high (polymer content is too low), the polymer may not be sufficiently present between the ceramic particles, resulting in incomplete binding problems between the ceramic particles and the polymer. When the content of the ceramic particles is too small (when the polymer content is too large), problems of lithium ion conduction disturbance due to an excessive amount of polymer may occur.

The ceramic composite electrolyte may have a viscosity of 1000 cP or more and 200000 cP or less. The viscosity may be adjusted to the above range so that the composite electrolyte has high elasticity and high durability. By having the viscosity within the above range, a composite electrolyte having high stretchability and high durability can be obtained.

Another embodiment of the present invention is a ceramic particle comprising ceramic particles; And a heat-resistant polymer; And a step of impregnating the solid electrolyte membrane with an ionic liquid, wherein the ionic liquid comprises a solvent and a lithium salt, wherein the total amount of the ceramic composite electrolyte is 100 wt% , At least 65 wt% and at most 95 wt% of the solid electrolyte membrane; Wherein the ionic liquid is contained in an amount of 5 wt% or more and 35 wt% or less.

Impregnating the solid electrolyte membrane with an ionic liquid, wherein the ionic liquid is impregnated with pores between different ceramic particles in the solid electrolyte membrane, between the ceramic particles and the polymer, or between different polymers .

By impregnating the ionic liquid in the above-described manner, the ionic liquid cell is formed on the surfaces of the ceramic particles and the polymer, so that the interfacial resistance between the ceramic particles and between the composite electrolyte and the electrode can be reduced. Further, the ionic liquid is a liquid at room temperature, and has excellent ionic conductivity, thermal stability, and electrochemical stability, thereby contributing to improvement in battery characteristics.

The solid electrolyte membrane, and the content of the ionic liquid have been described above, so they are omitted.

The ceramic particles; (Ceramic particles / heat-resistant polymer) to the heat-resistant polymer may be 2/1 or more and 5/1 or less, and in the step of preparing the solid electrolyte membrane containing the heat-resistant polymer, The reason is as described above.

Wherein the ionic liquid comprises at least 50% by weight and at most 95% by weight of solvent, based on 100% by weight of the total ionic liquid; 5% by weight or more, and 50% by weight or less of a lithium salt, and the reason for the limitation is as described above.

The ionic liquid may be prepared by stirring a mixture of the solvent and the lithium salt at a speed of not less than 40 rpm and not more than 2000 rpm. More specifically, it may be produced by stirring at a speed of 100 rpm or more and 500 rpm or less. If the stirring speed is too slow or too fast, it may not be sufficiently stirred.

The ionic liquid may be prepared by stirring a mixture of the solvent and the lithium salt for 6 hours or more and 24 hours or less. If the stirring time is too long or too short, the stirring may not be sufficiently performed .

The ionic liquid may be prepared by stirring a mixture of the solvent and the lithium salt at a temperature of 60 占 폚 or higher and 120 占 폚 or lower. If the agitation temperature is too low, incomplete dispersion problems may occur. If the stirring temperature is too high, volatilization of the solvent and decomposition of the polymer may occur.

Impregnating the solid electrolyte membrane with the ionic liquid may impregnate the solid electrolyte membrane with the ionic liquid for 30 minutes or more and for 24 hours or less by soaking the solid electrolyte membrane in the ionic liquid, Lt; / RTI &gt;

The types of the heat-resistant polymer, ceramic particles, solvent, and lithium salt are as described above.

According to another embodiment of the present invention, there is provided a ceramic composite electrolyte according to one embodiment of the present invention. anode; And a negative electrode. The content of the ceramic composite electrolyte is as described above.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the lithium metal alloy include lithium and a metal such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Q alloy (Q is an alkali metal, an alkaline earth metal, A transition metal, a rare earth element or a combination thereof and not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, A rare earth element or a combination thereof, but not Sn). The specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The anode includes a current collector and a cathode active material layer formed on the current collector.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, it is possible to use at least one of complex oxides of cobalt, manganese, nickel or a combination of metals and lithium, and specific examples thereof include compounds represented by any one of the following formulas. Li _a A _{1 - b} R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _{1 - b} R _b O _{2 - c} D _c , wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05; LiE _{2 - b} R _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -b- c} Co _b R _c D _{α where} 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2; Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z _{? Where} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -bc} Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z _{? Where} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1; Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise, as a coating element compound, an oxide, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

The cathode active material layer also includes a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Examples and Comparative Examples

Example 1

A slurry was obtained by vigorously stirring a solution in which 0.4 g of polyurethane (purchased from Aldrich) was dissolved in 1.6 g of Li ₇ La ₃ Zr ₂ O ₁₂ and N-methyl pyrrolidone (NMP, purchased from Aldrich).

Thereafter, the obtained slurry was poured onto a glass plate and pushed to a thickness of 100 mu m with a doctor blade (manufactured by Giga ENT). Thereafter, it was dried at room temperature to obtain a solid electrolyte membrane containing ceramic particles and polyurethane polymer.

The ionic liquid was prepared by adding 0.9 g of Py ₁₄ TFSI (purchased from Aldrich) and 0.1 g of LiTFSI (Aldrich) into a 20 mL vial and stirring the mixture at 100 ° C with a magnetic bar at 300 rpm for 12 hours.

Then, 0.4 g of the prepared ionic liquid and the solid electrolyte membrane were placed in a 20 mL vial glass bottle and impregnated in an argon (Ar) atmosphere for 24 hours to obtain a ceramic composite electrolyte.

Comparative Example 1

In Comparative Example 1, 1 M LiPF ₆ (EC / DMC) was used as a liquid electrolyte impregnated with a separator (Celgard).

Example 2

The surface of the composite electrolyte impregnated with the ionic liquid was wiped off the surface of the composite electrolyte to the extent that the liquid did not flow. The LiCoO ₂ anode having a diameter of 16 mm was placed on the bottom of the coin cell. And the cramping was performed by raising the spring, closing it with a cap, and cramping it.

Comparative Example 2

A 19 pi separator (celgard) was placed on the 1 lithium metal on the bottom of the coin cell, and then a general liquid electrolyte 1M LiPF ₆ (EC / DMC) was injected thereinto and then a 14 mm LiCoO ₂ anode was placed thereon. And then closed with a cap and cramped.

Experimental Example

Experimental Example  1: Measurement of dislocation window

The potential window of each coin cell was measured at a rate of 0.2 mV / s from 2 V to 7 V (vs. Li / Li ⁺ ) for the coin cell prepared in Example 2 and Comparative Example 2, respectively. Measurements were made with biologic impedance (manufacturer: biologic).

The measurement results are shown in Table 1 below. As can be seen from Table 1, the common liquid electrolyte prepared in Comparative Example 2 has a potential window of 4 V or less in the case of the used coin cell, whereas in the case of the coin cell using the ceramic composite electrolyte of Example 1 of the present invention, It has been confirmed that it can realize high electrochemical stability by having a classical scholar. Thus, it was confirmed that when using such a ceramic composite electrolyte, a high-voltage anode can be used in a lithium secondary battery.

Potential window (V vs. Li / Li ⁺ ) Example 1 5V Comparative Example 1 4V or less

Experimental Example 2: Measurement of ionic conductivity

The ceramic composite electrolyte of Example 1 was placed on the spacer, the spacer was again placed on the spacer, and the ionic conductivity was measured in a range of 100 MHz to 1 kHz by applying a constant voltage of 10 mV through a biologic impedance device (manufacturer: biologic) I got resistance. Ion conductivity of about 10 ^-4 S / cm was obtained by converting it by the equation of ion conductivity (σ = thickness / resistance * area).

On the other hand, a separator (Celgard) prepared by impregnating a liquid electrolyte of Comparative Example 1 with a general liquid electrolyte 1M LiPF ₆ (EC / DMC) was placed on a spacer, the spacer was placed on the spacer, A voltage was applied and the ion conductivity was measured in the range of 100 MHz to 1 kHz to obtain a resistance of about 60 Ω. Ion conductivity of about 10 ^-2 S / cm was obtained by the calculation of ion conductivity (σ = thickness / resistance * area).

The results are shown in FIG. 2. As described above, the ceramic composite electrolyte according to Example 1 of the present invention has an ion conductivity of about 10 ^-4 S / cm, and a typical ceramic solid electrolyte (about 10 ^-6 S / cm).

Experimental Example 3: Measurement of thermal stability

The ceramic composite electrolyte of Example 1 was subjected to thermogravimetric analysis using a differential scanning calorimeter (apparatus name: thermogravimetric analyzer (Q500, manufacturer: TA) at a heating rate of 2 ° C / min. , It was confirmed that the ceramic composite electrolyte of Example 1 did not lose its weight up to 400 DEG C and was stable. The ceramic composite electrolyte of Example 1 of the present invention was found to have stability at about 400 DEG C and thermal stability at high temperature It is judged that the weight lowered from 400 ° C or higher is due to the decomposition of the ionic liquid.

On the other hand, the liquid electrolyte of Comparative Example 1 was also subjected to thermogravimetric analysis in the same manner as described above. As shown in FIG. 3, it was confirmed through thermogravimetric analysis that the weight did not decrease to 100 ° C. and was stable. It is believed that the lowering weight from above 100 ° C is due to the decomposition of the common liquid electrolyte 1M LiPF ₆ (EC / DMC).

Experimental Example 4: Measurement of initial charge / discharge characteristics

When the coin cell of Comparative Example 2 was charged using a Wonatech cycler (manufacturer: Wonatech.Co) at a constant current rate of 0.5 mA and a voltage range of 3 V to 4.3 V (vs. Li / Li ⁺ ), The initial charge and discharge characteristics were evaluated by injecting a voltage range of ~ 3 V (vs. Li / Li ⁺ ) and a constant current rate of -0.5 mA. The result is shown in FIG. 4, and a capacity of about 160 mAh / g was obtained.

The coin cell of Example 2 was charged using a Wonatech cycler (manufacturer: Wonatech.Co) at a constant current rate of 0.5 mA and a voltage range of 3 V to 4.3 V (vs. Li / Li ⁺ ), The initial charge and discharge characteristics were evaluated by injecting a voltage range of ~ 3 V (vs. Li / Li ⁺ ) and a constant current rate of -0.5 mA. The result is shown in Fig. 4, and a capacity of about 140 mAh / g was obtained. This is equivalent to the case where a general liquid electrolyte or a ceramic electrolyte is used.

Experimental Example 5: Measurement of lifetime characteristics

The coin cell of Example 2 was charged using a Wonatech cycler (manufacturer: Wonatech.Co) at a constant current rate of 0.5 mA and a voltage range of 3 V to 4.3 V (vs. Li / Li ⁺ ), 50 cycle life characteristics were evaluated by injecting a voltage range of ~ 3 V (vs. Li / Li ⁺ ) and a constant current rate of -0.5 mA.

 The result is shown in FIG. 5, showing a capacity decrease of about 10 mAhg / g during 50 cycles and a capacity of about 130 mAh / g. That is, it showed a high lifetime characteristic of about 93%.

When the coin cell of Comparative Example 2 was charged using a Wonatech cycler (manufacturer: Wonatech.Co) at a constant current rate of 0.5 mA and a voltage range of 3 V to 4.3 V (vs. Li / Li ⁺ ), Lifetime characteristics were evaluated during 50cycles by injecting a voltage range of ~ 3V (vs. Li / Li ⁺ ) and a constant current rate of -0.5mA. A dose of about 150 mAh / g was obtained after a reduction of about 10 mAhg / g.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (23)

Ceramic particles; And a heat-resistant polymer, wherein the solid electrolyte membrane is impregnated with an ionic liquid,
Wherein the ionic liquid comprises a solvent and a lithium salt,
The ionic liquid is impregnated into pores in the solid electrolyte membrane,
At least 65 wt% and not more than 95 wt% of the solid electrolyte membrane, based on 100 wt% of the total amount of the ceramic composite electrolyte; 5 wt% or more and 35 wt% or less of the ionic liquid,
The solid electrolyte membrane is formed by forming an interconnected porous network in which the heat-resistant polymer is irregularly and continuously connected in a three-dimensionally continuous manner, and the ceramic particles in the interconnected pore structure are located And,
The ionic liquid is impregnated into pores between different ceramic particles in the solid electrolyte membrane, between the ceramic particles and the polymer, and / or between different polymers,
Wherein the heat-resistant polymer is polyurethane (PU), the ceramic particle is a garnet-type oxide,
Wherein the weight ratio (ceramic particle / heat resistant polymer) of the ceramic particles to the heat resistant polymer in the solid electrolyte membrane is 2/1 or more and 5/1 or less.
Ceramic composite electrolyte. delete delete The method of claim 1,
Wherein the ionic liquid comprises at least 50% by weight and at most 95% by weight of solvent, based on 100% by weight of the total ionic liquid; At least 5 wt%, and at most 50 wt% of a lithium salt.
Ceramic composite electrolyte. delete delete delete The method of claim 1,
Wherein the solvent is Py ₁₄ TFSI, Py ₁₃ TFSI, EMITFSI, BMITFSI, or a combination thereof.
Ceramic composite electrolyte. The method of claim 1,
Wherein the lithium salt, LiPF _6, LiClO _4, LiTFSI, or to a combination thereof,
Ceramic composite electrolyte. The method of claim 1,
Wherein the ceramic composite electrolyte has a viscosity of 1000 cP or more and 200000 cP or less,
Ceramic composite electrolyte. Ceramic particles; And a heat-resistant polymer, wherein an interconnected porous network is formed in the aggregate in which the heat-resistant polymer is three-dimensionally irregularly and continuously connected, and the interconnected porous network is formed by the heat-resistant polymer, Producing the solid electrolyte membrane such that the ceramic particles in the pore structure are located; And
And impregnating the solid electrolyte membrane with an ionic liquid,
Wherein the ionic liquid comprises a solvent and a lithium salt,
At least 65 wt% and not more than 95 wt% of the solid electrolyte membrane, based on 100 wt% of the total amount of the ceramic composite electrolyte; 5 wt% or more and 35 wt% or less of the ionic liquid,
In the step of impregnating the solid electrolyte membrane with the ionic liquid, the ionic liquid is impregnated into pores between different ceramic particles in the solid electrolyte membrane, between the ceramic particles and the polymer, or between different polymers,
Wherein the heat-resistant polymer is polyurethane (PU), the ceramic particle is a garnet-type oxide,
Wherein the weight ratio (ceramic particle / heat resistant polymer) of the ceramic particles to the heat resistant polymer in the solid electrolyte membrane is 2/1 or more and 5/1 or less.
A method for producing a ceramic composite electrolyte. delete delete 12. The method of claim 11,
Wherein the ionic liquid comprises at least 50% by weight and at most 95% by weight of solvent, based on 100% by weight of the total ionic liquid; At least 5 wt%, and at most 50 wt% of a lithium salt.
A method for producing a ceramic composite electrolyte. 12. The method of claim 11,
The ionic liquid may include,
And the mixture of the solvent and the lithium salt is stirred at a speed of 100 rpm or more and 500 rpm or less,
A method for producing a ceramic composite electrolyte. 16. The method of claim 15,
The ionic liquid may include,
And the mixture of the solvent and the lithium salt is stirred for not less than 6 hours and not longer than 24 hours.
A method for producing a ceramic composite electrolyte. 17. The method of claim 16,
The ionic liquid may include,
And the mixture of the solvent and the lithium salt is stirred at a temperature of 60 ° C or higher and 120 ° C or lower.
A method for producing a ceramic composite electrolyte. 12. The method of claim 11,
Impregnating the solid electrolyte membrane with an ionic liquid,
(Ar) atmosphere. &Lt; RTI ID = 0.0 &gt;
A method for producing a ceramic composite electrolyte. delete delete 12. The method of claim 11,
Wherein the solvent is Py ₁₄ TFSI, Py ₁₃ TFSI, EMITFSI, BMITFSI, or a combination thereof.
A method for producing a ceramic composite electrolyte. 12. The method of claim 11,
Wherein the lithium salt, LiPF _6, LiClO _4, LiTFSI, or to a combination thereof,
A method for producing a ceramic composite electrolyte. 10. A ceramic composite electrolyte as claimed in any one of claims 1 to 9,
anode; And
Cathode
Lithium secondary battery.

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