KR20200127769A - A solid electrolyte membrane and an all solid state lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a solid electrolyte membrane for an all-solid-state battery, wherein the solid electrolyte membrane includes two or more solid electrolyte layers and one or more volume expansion layers, and the volume expansion layers are disposed between the solid electrolyte layers. In addition, the solid electrolyte membrane includes an ion conductive solid electrolyte material (a), the volume expansion layers contain inorganic particles (B), and the inorganic particles are alloyed with lithium and contain metals, metal oxides, or both thereof. Accordingly, in the solid electrolyte membrane for an all-solid-state battery, a short circuit is fundamentally prevented by suppressing the growth of lithium dendrites.

Description

A solid electrolyte membrane and an all solid state lithium secondary battery comprising the same}

The present invention relates to an all-solid-state battery electrolyte membrane and an all-solid-state battery including the same.

A lithium ion battery using a liquid electrolyte has a structure in which a negative electrode and a positive electrode are partitioned by a separator, so if the separator is damaged by deformation or external impact, a short circuit may occur, which may lead to a risk of overheating or explosion. Therefore, it can be said that the development of a solid electrolyte that can secure safety in the field of lithium ion secondary batteries is a very important task.

A lithium secondary battery using a solid electrolyte has advantages in that the safety of the battery is increased, leakage of an electrolyte solution can be prevented, so that the reliability of the battery is improved, and it is easy to manufacture a thin-type battery.

However, in the solid electrolyte battery, lithium dendrites formed from the negative electrode grow and contact the positive electrode during battery operation, thereby causing a short circuit.

The present invention is to solve the above-described technical problem, by fundamentally inhibiting the growth of lithium dendrites and not generating a short circuit, thereby providing a solid electrolyte membrane for an all-solid battery with improved safety and an all-solid battery including the same. It is an object of the present invention. On the other hand, other objects and advantages of the present invention will be understood by the following description. In addition, it will be easily understood that the objects and advantages of the present invention can be realized by the means or methods described in the claims, and combinations thereof.

An aspect of the present invention provides a solid electrolyte membrane according to the following embodiments.

The first embodiment,

As a solid electrolyte membrane for an all-solid battery,

The solid electrolyte membrane includes an ion conductive solid electrolyte material (a); And lithium ions or inorganic particles (b) capable of intercalating lithium,

The inorganic particles are lithiumized by physically or chemically reacting with lithium ions, and include metals, metal oxides, or both, and are lithiumized to expand their volume,

The inorganic particles are located so as not to directly contact the electrode, relates to a solid electrolyte membrane.

The second embodiment, in the first embodiment,

The solid electrolyte membrane includes at least two solid electrolyte layers and at least one volume expansion layer, the volume expansion layer being disposed between the solid electrolyte layers,

The volume expansion layer includes the lithium ions or inorganic particles (B) capable of occluding lithium, which relates to a solid electrolyte membrane.

The third embodiment, in any one of the above-described embodiments,

The inorganic particles (B) relates to a solid electrolyte membrane having a volume expansion ratio of 10% to 1000% after lithiation compared to before lithiation.

In the fourth embodiment, in any one of the above-described embodiments,

The inorganic particles include Si, Sn, SiO, SnO, MnO ₂ , Fe ₂ O ₃ or two or more of them, relates to a solid electrolyte membrane.

In the fifth embodiment, in any one of the above-described embodiments,

The inorganic particles (B) is 1 to 30% by weight based on 100% by weight of the solid electrolyte membrane, relates to a solid electrolyte membrane.

In the sixth embodiment, in any one of the above-described embodiments,

The thickness of the volume expansion layer is 10 nm to 50 ㎛, relates to a solid electrolyte membrane.

In the seventh embodiment, in any one of the above-described embodiments,

The ion conductive solid electrolyte material (a) has an ion conductivity of 10 ^-5 S/cm or more, and includes a polymer-based solid electrolyte, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or two or more of them. It relates to an electrolyte membrane.

In the eighth embodiment, in the second embodiment,

The volume expansion layer relates to a solid electrolyte membrane that contains the inorganic particles at a high concentration.

Another aspect of the present invention provides an all-solid-state battery according to the following embodiments.

The ninth embodiment,

As an all-solid battery,

The all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between the positive electrode and the negative electrode,

The solid electrolyte membrane is a solid electrolyte membrane according to any one of the above-described embodiments, and relates to an all-solid-state battery.

In the tenth embodiment, in the ninth embodiment,

The solid electrolyte membrane includes a first solid electrolyte layer, a second solid electrolyte layer, and a volume expansion layer, the volume expansion layer being disposed between the solid electrolyte layers,

The volume expansion layer includes the lithium ions or inorganic particles (B) capable of occluding lithium,

The first solid electrolyte layer faces the negative electrode,

It relates to an all-solid-state battery in which the thickness of the first solid electrolyte layer is greater than that of the second solid electrolyte layer.

The solid electrolyte membrane according to the present invention contains lithium or lithium ions and inorganic particles that expand in volume by lithiation, thereby inhibiting the growth of lithium dendrites and fundamentally does not cause a short circuit, thereby improving safety. And it is possible to provide an all-solid-state battery including the same.

The drawings appended to the present specification illustrate preferred embodiments of the present invention, and serve to better understand the technical idea of the present invention together with the content of the above-described invention, so the present invention is limited to the matters described in such drawings. Is not interpreted. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in the present specification may be exaggerated to emphasize a clearer description.
1 is a schematic diagram of a problem in which a short circuit is caused by growth of lithium dendrites from a negative electrode in a conventional all-solid-state battery.
2 is for an all-solid-state battery including a solid electrolyte membrane according to an embodiment of the present invention, and schematically shows a reaction in which lithium dendrite growth is inhibited by inorganic particles or a volume expansion layer including the same.

Hereinafter, embodiments of the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention. Therefore, the configuration described in the embodiments described in the present specification is only the most preferred embodiment of the present invention, and does not represent all the technical spirit of the present invention, and various equivalents that can replace them at the time of application It should be understood that there may be variations.

In the entire specification of the present application, when a certain part "includes" a certain constituent element, it means that other constituent elements may be further included instead of excluding other constituent elements unless otherwise stated.

In addition, the terms "about" and "substantially" used throughout the specification of the present application are used as a meaning at or close to the numerical value when a manufacturing and material tolerance inherent to the stated meaning is presented to aid understanding of the present application. In order to prevent unreasonable use by unscrupulous infringers of the stated disclosures, either exact or absolute figures are used.

In the entire specification of the present application, the description of "A and/or B" means "A or B or both".

Certain terms used in the detailed description that follow are for convenience and are not limiting. The words “right”, “left”, “top” and “bottom” indicate directions in the drawings to which reference is made. The words'inwardly' and'outwardly' refer to a direction towards or away from the geometric center of a specified device, system and members, respectively. 'Forward','rear','upward','downward' and related words and phrases represent positions and orientations in the drawings to which reference is made, and should not be limited. These terms include the words listed above, their derivatives and words of similar meaning.

The present invention relates to a solid electrolyte membrane for an all-solid-state battery and an all-solid-state battery including the same. The solid electrolyte membrane for an all-solid battery according to the present invention includes inorganic particles that are alloyed with lithium in the volume expansion layer, so that a short circuit is fundamentally prevented, thereby providing an all-solid battery with improved safety.

1 is a schematic diagram of a problem in which a short circuit is caused by growth of lithium dendrites from a negative electrode in a conventional all-solid-state battery. 2 is for an all-solid-state battery including a solid electrolyte membrane according to an embodiment of the present invention, schematically showing a reaction in which lithium dendrite growth is suppressed by a volume expansion layer containing inorganic particles. Hereinafter, the present invention will be described in more detail with reference to the drawings.

Referring to FIG. 1, a conventional solid electrolyte membrane is generally formed in a layered structure by integrating particulate ion-conducting inorganic materials, and contains a large number of pores due to interstitial volumes between particles. Accordingly, as a space provided by the pores, lithium dendrites grown from the negative electrode contact the positive electrode, causing a short circuit.

On the other hand, since the solid electrolyte membrane for an all-solid battery according to the present invention includes the inorganic particles (B), it is possible to fundamentally suppress a short circuit due to the growth of lithium dendrites during battery operation.

Specifically, the solid electrolyte membrane for an all-solid-state battery according to the present invention includes inorganic particles located in a place not in direct contact with a negative electrode. The inorganic particles are electrically connected to the negative electrode by directly contacting the lithium dendrite generated in the negative electrode during battery operation, and the inorganic particles exhibit a negative electrode potential. Accordingly, the inorganic particles can act like a negative active material. Thereafter, lithium grown from lithium ions or lithium dendrites supplied from the positive electrode according to the battery operation is physically or chemically reacted with the inorganic particles to be lithiumized.

In this case, the lithium may be a lithium atom itself. When the lithium is in contact with the inorganic particles by lithium dendrites, it has electrical conductivity and can exhibit a negative electrode potential, so that it can be lithiumized by contacting the inorganic particles.

As shown in FIG. 2, the lithiated inorganic particles expand in volume, and dead spaces or voids occur in the solid electrolyte membrane. Since ions cannot be transferred to the generated dead space or voids, the resistance within the electrode assembly increases rapidly, and the growth of lithium dendrites may be stopped. Accordingly, it is possible to fundamentally suppress the short circuit between the cathode and the anode.

In the solid electrolyte membrane according to an aspect of the present invention, the solid electrolyte membrane comprises an ion conductive solid electrolyte material (A); And lithium ions or inorganic particles (B) capable of occluding lithium.

In other words, the inorganic particles (B) may contain lithium ions or lithium in the inorganic particles. In this case, lithium ions or lithium reacts physically or chemically with the inorganic particles to be complexed with the inorganic particles.

Accordingly, after the inorganic particles (B) are lithium ions or lithium and lithium ions, the lithium ions or lithium cannot be desorbed, and cannot be recovered before being lithiated. In other words, as ions cannot be transferred due to the occurrence of voids or dead spaces, or lithium dendrites are separated from lithium dendrites due to discharge and become electrically insulated, the lithium-formed inorganic particles cannot be separated from lithium, and are recovered before being lithiated. It can be impossible.

The inorganic particles (B) according to the present invention are lithium ions or lithium ions that are physically or chemically reacted with lithium and contain metals, metal oxides, or both.

Specifically, the lithiation may be that when the inorganic particles are metal, the metal inorganic particles are lithiumized in the form of lithium ions or an alloy with lithium.

Specifically, the lithiation may be that when the inorganic particles are metal oxides, the metal oxide inorganic particles are combined with lithium ions or lithium to chemically bond with lithium.

More specifically, the lithiation may be a reaction of inorganic particles as shown in Equation 1:

[Equation 1]

X(Li) + Y(M) -> LixMy

In this case, M is Si, Sn, SiO, SnO, MnO2, or two or more of these, and x and y are determined according to the oxidation number of M, and X and Y are integers of 1 or more. to be.

Even when the inorganic particles contain both metals or metal oxides, the above reaction may be similarly applied.

The inorganic particles (B) according to the present invention are lithium ions or lithium and the volume expands.

That is, in the present invention, by using inorganic particles capable of volume expansion, voids can be generated in the solid electrolyte membrane as the battery is driven. The generation of such voids can fundamentally limit the movement of lithium ions or lithium, and as the resistance of the battery increases, the battery can be degraded without a micro short circuit. That is, according to an aspect of the present invention, it is possible to fundamentally prevent a safety problem due to a short circuit in advance.

To this end, the inorganic particles (B) according to the present invention are positioned so as not to directly contact the electrode. In other words, the inorganic particles are located inside the solid electrolyte membrane, and may fundamentally inhibit the growth of lithium dendrites generated as the battery is driven.

On the other hand, in one aspect of the present invention, the inorganic particles are preferably concentrated in order to generate voids by volume expansion in the solid electrolyte membrane.

In a specific embodiment of the present invention, the inorganic particles may have a volume expansion ratio of 10 to 1000%, or 20 to 500%, or 50 to 300%, compared to before being lithiated, that is, the present invention When the inorganic particles (B) are lithium ions or lithium and lithium, they become lithified inorganic particles (C), and the lithiated inorganic particles (C) have a significantly larger volume than the inorganic particles (B). will be.

In this case, the lithiated inorganic particles (C) may be the same as in Formula 1:

[Equation 1]

LixMy

In this case, M is Si, Sn, SiO, SnO, MnO2, or two or more of them, and x and y are determined according to the oxidation number of M.

In one embodiment of the present invention, the inorganic particle (B) contains a metal or a metal oxide. Specifically, the inorganic particles may include Si, Sn, SiO, SnO, MnO ₂ , Fe ₂ O ₃ or two or more of them.

In particular, Si is suitable for solving the problem according to an aspect of the present invention in that the volume expansion ratio after lithiation reaches about 300% compared to before lithiation.

In a specific embodiment of the present invention, the inorganic particles (B) may be included in 1 to 30% by weight, or 2 to 20% by weight, or 5 to 10% by weight based on 100% by weight of the solid electrolyte membrane.

In a specific embodiment of the present invention, the solid electrolyte membrane includes at least two solid electrolyte layers and at least one volume expansion layer, the volume expansion layer being disposed between the solid electrolyte layers,

The volume expansion layer may include the ion conductive solid electrolyte material (a) and inorganic particles (B).

In the volume expansion layer, the inorganic particles may be dispersed evenly or in a non-uniform distribution throughout the volume expansion layer.

In one embodiment of the present invention, the volume expansion layer may have a patterned form in a manner in which panel units including inorganic particles are regularly or irregularly arranged in the volume expansion layer. The pattern unit may include only inorganic particles or, if necessary, a mixture of inorganic particles and a solid electrolyte material. Meanwhile, the uncoated portion that may exist between the pattern units may be buried with a solid electrolyte layer stacked on the upper and lower portions of the volume expansion layer, or may be filled with a separate solid electrolyte material.

In a specific embodiment of the present invention, the thickness of the volume expansion layer is less than 50 μm, preferably 10 μm or less, for example, 1 μm or less, 100 nm or less, or 10 nm or less on a nanometer scale. It can be formed thin.

The volume expansion layer contains inorganic particles in a higher concentration than other layers (for example, a solid electrolyte layer). For example, the inorganic particles may be contained in a range of 30% to 100% by weight based on 100% by weight of the volume expansion layer. The content of the inorganic particles may be 50% by weight or more, or 80% by weight or more, or 90% by weight or more within the above range. As the content of the inorganic particles is high, the decrease in ionic conductivity is small, and unnecessary amounts in the solid electrolyte membrane can be minimized. On the other hand, within the above numerical range, the solid electrolyte membrane according to an aspect of the present invention can fundamentally inhibit lithium dendrite growth.

In one embodiment of the present invention, the volume expansion layer may be coated with less than 90%, less than 50%, or less than 30% of the surface 100% of the surface of the solid electrolyte layer. As the volume expansion layer is covered within the above numerical range, the reduction in ion conductivity can be minimized and the safety improvement effect of the present invention can be maximized.

In one embodiment of the present invention, the thickness of the volume expansion layer, the concentration of inorganic particles, the area in which the volume expansion layer covers the solid electrolyte layer, etc. may be appropriately adjusted in consideration of the ionic conductivity of the solid electrolyte membrane. That is, the volume expansion layer included in the solid electrolyte membrane includes the thickness of the volume expansion layer, the concentration of inorganic particles, and the volume expansion layer so that the solid electrolyte membrane exhibits ionic conductivity of 1x10 ^-5 S/cm or more. The covering area can be adjusted to have an appropriate range.

The solid electrolyte membrane according to an aspect of the present invention includes two or more solid electrolyte layers and at least one volume expansion layer, and the volume expansion layer is disposed between the solid electrolyte layers.

For example, the solid electrolyte membrane may have a layered structure in which a first solid electrolyte layer, a volume expansion layer, and a second solid electrolyte layer are sequentially stacked. Alternatively, the solid electrolyte membrane may be provided with first, second and third solid electrolyte layers, a first volume expansion layer between the first and second solid electrolyte layers, and between the second and third solid electrolyte layers A second volumetric expansion layer may be disposed. That is, the volume expansion layer may have a structure in which inorganic particles included in the volume expansion layer do not directly contact the anode and/or the cathode. Each of the volume expansion layers is independent of each other in terms of shape or material, and one of the volume expansion layers may be the same as or different from the other. Each of the solid electrolyte layers is independent of each other in terms of shape or material, and one solid electrolyte layer may be the same as or different from the other.

In one embodiment of the present invention, the solid electrolyte membrane may be formed by the following method. However, it is not limited thereto.

First, a first solid electrolyte layer is prepared.

Thereafter, a polymer solution is prepared using an ion conductive solid electrolyte material in a solvent, and inorganic particles are added to the polymer solution to prepare a composition for forming a volume expansion layer. The polymer solution and composition may be subjected to a stirring process for uniform dispersion of the added components in the solvent.

Meanwhile, in the present invention, the solvent may include at least one selected from toluene, tetrahydrofuran, ethylene, acetone, chloroform, and dimethylformamide (DMF).

Next, the composition for forming the volume expansion layer may be coated on the prepared first solid electrolyte layer, and then a second solid electrolyte layer may be laminated. In this case, the first solid electrolyte layer may be a layer facing the negative electrode.

In the present invention, the solid electrolyte membrane has an ionic conductivity of 1x10 ^-7 S/cm or more, or 1x10 ^-6 S/cm or more in a state in which the volume expansion layer is included. In this case, the ionic conductivity is a value obtained by measuring the all-solid-state battery including the solid electrolyte membrane at a normal driving temperature.

In one embodiment of the present invention, the solid electrolyte membrane may have a thickness in the range of 10 μm to 500 μm. For a specific example, the thickness of the solid electrolyte membrane may be 20 µm to 100 µm, or 30 µm to 60 µm. It is possible to provide a solid electrolyte membrane having an appropriate physical strength and an appropriate lithium ion conductivity within the above numerical range.

The solid electrolyte membrane includes two or more solid electrolyte layers. The solid electrolyte layer includes an ion conductive solid electrolyte material (a), and may be applied as an ion conductive electrolyte to an all-solid battery that does not use a liquid electrolyte, for example. The ion conductive solid electrolyte material may have an ion conductivity of 10 ^-5 S/cm or more.

The solid electrolyte material may include a polymer solid electrolyte, an inorganic solid electrolyte, or a mixture of both.

In one embodiment of the present invention, the polymer-based solid electrolyte contains a polymer resin and a lithium salt, and is a solid polymer electrolyte in the form of a mixture of a solvated lithium salt and a polymer resin, or contains an organic solvent and a lithium salt. It may be a polymer gel electrolyte in which one organic electrolyte is contained in a polymer resin.

In one embodiment of the present invention, the solid polymer electrolyte is a polymer resin, for example, a polyether polymer, a polycarbonate polymer, an acrylate polymer, a polysiloxane polymer, a phosphazene polymer, a polyethylene derivative, an alkylene. Oxide derivatives, phosphoric acid ester polymers, poly agitation lysine (agitation lysine), polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociation group, or two or more of these may be included, It is not limited thereto.

In a specific embodiment of the present invention, the solid polymer electrolyte is a polymer resin in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane (pdms), and/or phosphazene is copolymerized with a comonomer in a PEO (polyethylene oxide) main chain. It may include a branched copolymer, a comb-like polymer, a crosslinked polymer resin, or two or more of them.

In addition, in a specific embodiment of the present invention, the polymer gel electrolyte includes an organic electrolyte containing a lithium salt and a polymer resin, and the organic electrolyte may include 60 to 400 parts by weight based on 100 parts by weight of the polymer resin. . The polymer resin applied to the gel electrolyte is not limited to specific components, but for example, PVC (Polyvinyl chloride), PMMA (Poly (methyl methacrylate)), polyacrylonitrile (PAN), polyvinyl fluoride Liden (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), or a mixture of two or more of them may be included, but the present invention is not limited thereto.

In the electrolyte of the present invention, the lithium salt described above is an ionizable lithium salt, which can be expressed as Li ⁺ X ⁻ . In this lithium salt anion (X) is not particularly ^{limited, F -, Cl -, Br} -, I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, ( ^{_{CF 3) 2 PF 4 -,}} (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 ^{_{CF 2 SO 3 -, (CF}} 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) _{^{3 C -, (CF 3 SO}} 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN -, (CF 3 CF 2 SO 2) 2 N ^- and the like can be given.

Meanwhile, in a specific embodiment of the present invention, the polymer solid electrolyte may further include an additional polymer gel electrolyte. The polymer gel electrolyte has excellent ionic conductivity (or 10 ^-4 S/cm or more), has a binding property, provides a function as an electrolyte, and provides a binding force between an electrode active material and an electrode layer and a current collector. The function of the electrode binder resin to be provided can be provided.

Meanwhile, in the present invention, the solid electrolyte membrane may further include a crosslinking agent and/or an initiator when preparing the solid electrolyte layer when a polymer material is used as an electrolyte material for the solid electrolyte layer. The crosslinking agent and/or initiator may initiate a crosslinking reaction or polymerization reaction depending on heat, light, and/or temperature conditions, and are not limited to a special component as long as it can induce crosslinking and/or polymerization of a polymer material. In one embodiment of the present invention, an organic peroxide, an organometallic reagent such as silver alkylation, an azo compound, etc. may be used as the crosslinking agent and/or initiator, but is not limited thereto.

Meanwhile, in the present invention, the inorganic solid electrolyte may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or both.

In a specific embodiment of the present invention, the sulfide-based solid electrolyte includes a sulfur atom among the electrolyte components, and is not particularly limited to specific components, and is crystalline solid electrolyte, amorphous solid electrolyte (glassy solid electrolyte), and glass ceramic. It may contain one or more of the solid electrolytes. Specific examples of the sulfide-based solid electrolyte include LPS-type sulfide containing sulfur and phosphorus, Li _{4 - x} Ge _{1 - x} P _x S ₄ (x is 0.1 to 2, specifically x is 3/4, 2/3 ), Li _{10 ± 1} MP ₂ X ₁₂ (M=Ge, Si, Sn, Al, X=S, Se), Li _3.833 Sn _0.833 As _0.166 S ₄ , Li ₄ SnS ₄ , Li _{3 . 25} Ge _{0 .25} P _{0. 75} S ₄ , Li ₂ SP ₂ S ₅ , B ₂ S ₃ -Li ₂ S, xLi ₂ S-(100-x)P ₂ S ₅ (x is 70 to 80), Li _{2 s-SiS 2 -Li 3 N} , Li 2 SP 2 s 5 - , and the like _{LiI, Li 2 s-SiS 2} -LiI, Li 2 SB 2 s 3 -LiI but is not limited to this.

In a specific exemplary embodiment of the present invention, the oxide-based solid electrolyte, for example, Li _3x LLT based on La _{2 / 3x} perop Sky imide structure such as _{TiO 3, Li 14 Zn (GeO} 4) , such as ₄ LISICON, Li _{1 . 3} Al _{0 . 3} Ti _{1 . 7} LATP type such as (PO ₄ ) ₃ , LAGP type such as (Li _{1 + x} Ge _{2 - x} Al _x (PO ₄ ) ₃ ), phosphate type such as LiPON can be appropriately selected and used. It is not limited.

Meanwhile, in a specific embodiment of the present invention, the composition of the ion conductive solid electrolyte included in the first and second solid electrolyte layers may be the same or different from each other. For example, the first layer may include an oxide-based solid electrolyte material, and the second layer may include a sulfide-based solid electrolyte material.

In one embodiment, the solid electrolyte membrane may be formed by forming a volume expansion layer on the surface of the first solid electrolyte layer and then forming a second solid electrolyte layer on the surface of the volume expansion layer. If two or more volume expansion layers are included, a method of forming a volume expansion layer on the surface of the second solid electrolyte layer and then forming a third solid electrolyte layer thereon may be prepared. In one embodiment of the present invention, in the case of manufacturing a solid electrolyte membrane including a volume expansion layer or a solid electrolyte layer more than this, a method of forming a volume expansion layer and a solid electrolyte layer may be repeatedly performed.

Another aspect of the present invention provides an all-solid-state battery including the above-described solid electrolyte membrane. The all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane, and the solid electrolyte membrane includes the above-described solid electrolyte membrane.

In a specific embodiment of the present invention,

The solid electrolyte membrane includes a first solid electrolyte layer, a second solid electrolyte layer, and a volume expansion layer, and the volume expansion layer is disposed between the solid electrolyte layers,

The volume expansion layer includes inorganic particles (B) in which the lithium is occluded,

The first solid electrolyte layer faces the negative electrode,

The thickness of the first solid electrolyte layer may be greater than the thickness of the second solid electrolyte layer.

As described above, as the thickness of the first solid electrolyte layer close to the negative electrode is thicker than the thickness of the second solid electrolyte layer further away from the negative electrode, the growth of lithium dendrites can be more effectively suppressed, thereby improving safety.

In the present invention, the positive electrode and the negative electrode have a current collector and an electrode active material layer formed on at least one surface of the current collector, and the active material layer includes a plurality of electrode active material particles and a solid electrolyte. In addition, the electrode may further include at least one of a conductive material and a binder resin as necessary. In addition, the electrode may further include various additives for the purpose of supplementing or improving physicochemical properties of the electrode.

In the present invention, the negative electrode may include a current collector and a negative electrode active material layer formed on the surface of the current collector, and any material that can be used as a negative active material for a lithium secondary battery may be used as the negative active material. For example, the negative active material may include carbon such as non-graphitized carbon and graphite-based carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _{1 -x} Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me' : Al, B, P, Si, elements of groups 1, 2 and 3 of the periodic table, halogen, metal complex oxides such as 0<x≦1;1≦y≦3;1≦z≦8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , And metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; One or two or more selected from lithium titanium oxide may be used.

In a specific embodiment, the negative active material layer may include at least one element belonging to an alkali metal, an alkaline earth metal, a group 3B, and a transition metal. In a specific embodiment of the present invention, the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) or francium (Fr) as non-limiting examples of the alkali metal At least one or more metals selected from are mentioned, and preferably lithium is included. In a specific embodiment of the present invention, the negative electrode may be laminated by bonding a negative electrode current collector and a lithium metal thin film having a predetermined thickness by compression bonding. Alternatively, it may be a lithium metal thin film or a current collector itself.

In the case of the positive electrode, the electrode active material may be used without limitation as long as it can be used as a positive electrode active material for a lithium ion secondary battery. For example, the positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as the formula Li _{1 + x} Mn _{2 - x} O ₄ (wherein x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, etc.; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _{1 - x} M _x O ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 ~ 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, A lithium manganese composite oxide represented by Ni, Cu or Zn); A lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _{2 - x} O ₄ ; LiMn ₂ O _{4 wherein} part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like. However, it is not limited only to these.

In the present invention, the current collector may exhibit electrical conductivity such as a metal plate, and may be appropriate according to the polarity of the current collector electrode known in the field of secondary batteries.

In the present invention, the conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; It may include one or a mixture of two or more selected from conductive materials such as polyphenylene derivatives.

In the present invention, the binder resin is not particularly limited as long as it is a component that aids in bonding of an active material and a conductive material and bonding to a current collector, and for example, polyvinylidene fluoride polyvinyl alcohol, carboxymethylcellulose (CMC ), starch, hydroxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, Fluorine rubber and various copolymers. The binder resin may be included in a range of 1 to 30% by weight, or 1 to 10% by weight, based on 100% by weight of the electrode layer.

Meanwhile, in the present invention, the electrode active material layer may include one or more additives such as an oxidation stabilizer additive, a reduction stabilizer additive, a flame retardant, a heat stabilizer, and an antifogging agent, if necessary.

In the present invention, the solid electrolyte may further include one or more of a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte.

In the present invention, the solid electrolyte may be different for a positive electrode, a negative electrode, and a solid electrolyte membrane, or the same one may be used for two or more battery elements. For example, in the case of the positive electrode, a polymer electrolyte having excellent oxidation stability may be used as a solid electrolyte. In addition, in the case of the negative electrode, it is preferable to use a polymer electrolyte having excellent reduction stability as a solid electrolyte. However, the present invention is not limited thereto, and since it mainly serves as a transfer role of lithium ions in the electrode, any material having high ionic conductivity, for example, 10 ^-7 S/cm or more or 10 ^-6 S/cm or more can be used. It is not limited to ingredients.

In the present invention, the polymer electrolyte may be a solid polymer electrolyte formed by adding a polymer resin to each independently solvated lithium salt, or a polymer gel electrolyte containing an organic electrolyte containing an organic solvent and a lithium salt in the polymer resin. have.

In the present invention, the polymer electrolyte may refer to the description of the solid electrolyte membrane.

The sulfide-based solid electrolyte contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS-based glass or Li-PS-based glass ceramic. Non-limiting examples of such sulfide-based solid electrolytes include Li ₂ SP ₂ S ₅ , Li ₂ S-LiI-P ₂ S ₅ , Li ₂ S-LiI-Li ₂ OP ₂ S ₅ , Li ₂ S-LiBr-P ₂ S ₅ , Li ₂ S-Li ₂ OP ₂ S ₅ , Li ₂ S-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP ₂ S ₅ -P ₂ O ₅ , Li ₂ SP ₂ S ₅ -SiS ₂ , Li ₂ SP ₂ S ₅ -SnS, Li ₂ SP ₂ S ₅ -Al ₂ S ₃ , Li ₂ S-GeS ₂ , Li ₂ S-GeS ₂ -ZnS, and the like, and may contain one or more of them. have.

In addition, the oxide-based solid electrolyte contains oxygen (O) and has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. Non-limiting examples thereof include LLTO-based compounds, Li ₆ La ₂ CaTa ₂ O ₁₂ , Li ₆ La ₂ ANb ₂ O ₁₂ (A is Ca or Sr), Li ₂ Nd ₃ TeSbO ₁₂ , Li ₃ BO _2.5 N _0.5 , Li ₉ SiAlO ₈ , LAGP compound, LATP compound, Li _{1 + x} Ti _{2 - x} Al _x Si _y (PO ₄ ) _{3 -y} (here, 0≤x≤1, 0≤y≤1), LiAl _x Zr _{2 -x} (PO ₄ ) ₃ (here, 0≤x≤1, 0≤y≤1), LiTi _x Zr _{2 -x} (PO ₄ ) ₃ (here, 0≤x≤1, 0≤y ≤1), LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, Nasicon-based compounds, and may include at least one selected from LLZO-based compounds.

In addition, the present invention provides a secondary battery having the above-described structure. In addition, the present invention provides a battery module including the secondary battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. In this case, a specific example of the device may include a power tool that is driven by an electric motor; Electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf cart; Power storage systems, etc., but are not limited thereto.

Hereinafter, the present invention will be described in more detail through examples, but the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example One

1. Manufacture of solid electrolyte membrane

(1) Preparation of the first solid electrolyte layer and the second solid electrolyte layer

A polymer solution of 4 wt% was prepared by dissolving polyethylene oxide (PEO, weight average molecular weight (Mw) 4,000,000 g/mol) in acetonitrile (AN) solvent. At this time, LiTFSI was added together as a lithium salt so that [EO]/[Li+]=18/1 (molar ratio). The polymer solution was stirred overnight at 70° C. so that PEO and lithium salt were sufficiently dissolved. Next, an additive solution including an initiator and a curing agent was prepared. PEGDA (Mw=575) as the curing agent and benzoyl peroxide (BPO) as the initiator are used, and the amount of polyethylene glycol diacrylate (PEGDA) is 20 wt% compared to PEO, and BPO is 1% PEGDA. And acetonitrile was used as a solvent. The additive solution was stirred for about 1 hour so that the added components were well mixed. Thereafter, the additive solution was added to the polymer solution, and the two solutions were sufficiently mixed. The mixed solution was applied and coated on a release film using a doctor blade. The coating gap was 800 μm, and the coating speed was 20 mm/min. The release film coated with the solution was moved to a glass plate to maintain the level well, dried overnight at room temperature, and vacuum dried at 100°C for 12 hours. In this way, a first solid electrolyte layer and a second solid electrolyte layer were obtained. The thickness of the obtained first solid electrolyte layer and the second solid electrolyte layer was about 50 μm.

(2) Preparation of volume expansion layer

An inorganic particle dispersion was prepared by dispersing Si (Sigma-Aldrich, <100 nm) as inorganic particles in an NMP solvent at a concentration of 1 wt% through sonication. The prepared dispersion was spin coated at 1 wt% of the first solid electrolyte layer to form a volume expansion layer on the first solid electrolyte layer.

(3) Structure of a multilayered solid electrolyte membrane

The first solid electrolyte layer coated with the volume expansion layer and the prepared second solid electrolyte layer were stacked and stacked, and the interval between the rolls was adjusted to 100 μm, followed by calendering at 60°C. At this time, a volume expansion layer was arranged between the first and second solid electrolyte layers. In this way, a solid electrolyte membrane in which a first solid electrolyte layer, a volume expansion layer, and a second solid electrolyte layer were sequentially stacked was obtained. The thickness of the obtained solid electrolyte membrane was about 100 μm.

2. Anode Manufacturing

To the slurry produced electrode active material is _{NCM811 (... LiNi 0 8} Co 0 1 Mn 0 1 O 2), conductive material VGCF (Vapor grown carbon fiber) and the high-molecular solid solid electrolyte (PEO + LiTFSI, 18: 1 mol ratio ) Was mixed at a weight ratio of 80:3:17, added to acetonitrile, and stirred to prepare an electrode slurry. This was applied to an aluminum current collector having a thickness of 20 μm using a doctor blade, and the resultant was vacuum-dried at 120° C. for 4 hours. Thereafter, the vacuum drying result was subjected to a rolling process using a roll press to obtain an electrode having an electrode loading of 2mAh/cm ^2, an electrode layer thickness of 48 μm, and a porosity of 22%.

3. Manufacture of battery

The prepared positive electrode was prepared by punching in a circular shape of 1.4875 cm ² . A lithium metal thin film cut into a circular shape of 1.7671 cm ² was prepared as a negative electrode. A coin-type half-cell was manufactured by placing the prepared solid electrolyte membrane between the two electrodes. At this time, the volume expansion layer was prepared so that the other surface of the first solid electrolyte layer to face the negative electrode.

Example 2

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the prepared dispersion was spin coated at 5 wt% of the first solid electrolyte layer to form a volume expansion layer on the first solid electrolyte layer.

Example 3

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the volume expansion layer was prepared by the following method. Specifically, Si (Sigma-Aldrich, <100nm) as inorganic particles, 0.5wt% PEO + LiTFSI in NMP solvent, [PEO]/[Li+]=18/1 (molar ratio) added to the NMP solution at 5 wt% concentration By dispersing through sonication, an inorganic particle dispersion was prepared. The prepared dispersion was spin coated at 1 wt% of the first solid electrolyte layer to form a volume expansion layer on the first solid electrolyte layer.

Example 4

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the volume expansion layer was prepared by the following method. Specifically, SnO2 (Sigma-Aldrich, <100nm) was used instead of Si (Sigma-Aldrich, <100nm) as inorganic particles, and the dispersion containing the inorganic particles was spin coated at 5 wt% compared to the first solid electrolyte layer Thus, a volume expansion layer was formed on the first solid electrolyte layer.

Example 5

The first solid electrolyte layer was prepared so that the thickness of the first solid electrolyte layer was 30 μm and the second solid electrolyte layer was 70 μm, and the dispersion containing inorganic particles was spin-coated at 5 wt% compared to the first solid electrolyte layer. A solid electrolyte membrane was prepared in the same manner as in Example 1, except that a volume expansion layer was formed on the electrolyte layer. That is, Example 5 is a case in which the thickness of the first solid electrolyte layer close to the cathode is thinner than the thickness of the second solid electrolyte layer relatively far from the cathode.

Example 6

The first solid electrolyte layer was prepared so that the thickness of the first solid electrolyte layer was 70 μm and the second solid electrolyte layer was 30 μm, and the dispersion containing inorganic particles was spin-coated at 5 wt% compared to the first solid electrolyte layer. A solid electrolyte membrane was prepared in the same manner as in Example 1, except that a volume expansion layer was formed on the electrolyte layer. That is, Example 6 is a case where the thickness of the first solid electrolyte layer close to the cathode is greater than the thickness of the second solid electrolyte layer relatively far from the cathode.

Comparative example One

A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that a volume expansion layer including inorganic particles was not provided.

The results of Examples 1 to 6 and Comparative Example 1 are summarized in Table 1 below.

Evaluation experiment

Measurement of ionic conductivity of solid electrolyte membrane

The solid electrolyte membrane obtained in each Example and Comparative Example was punched out into a circular shape having a size of 1.7671 cm ² and placed between two sheets of stainless steel to prepare a coin cell. An analysis device (VMP3, Bio logic science instrument) was used to measure the electrochemical impedance at an amplitude of 10mV and a scan range of 500khz to 0.1mHz at 60°C, and ionic conductivity was calculated based on this.

Initial discharge capacity evaluation

Initial discharge capacity was measured by charging and discharging the fabricated battery at 60°C.

Charging condition: CC/CV (4.0V, 0.05C-rate, 0.005C current cut-off)

Discharge condition: CC (3V, 0.05C-rate)

After the initial discharge capacity evaluation, charging and discharging was performed at 0.05 C-rate, and the time of formation of Li dendrite was confirmed during life evaluation.

Ion conductivity
(S/cm@60 ℃) Discharge capacity
(mAh/g, 4V) Short occurrence point (cycle) Example 1 1*10 ^-4 119 9 Example 2 9*10 ^-5 117 8 Example 3 9*10 ^-5 118 8 Example 4 9*10 ^-5 114 11 Example 5 9*10 ^-5 116 5 Example 6 9*10 ^-5 115 14 Comparative Example 1 1E ^-04 120 17

As shown in Table 1, the same electrode is used, and it can be seen that the time point of occurrence of the short is different due to the difference in the solid electrolyte film. The battery of Comparative Example 1 eventually generates a micro-short by Li dendrite in 17 cycles, and there is a risk of ignition or explosion when additionally driven thereafter. On the other hand, in the case of the embodiment, instead of generating a microshort when Li dendrite meets the positive electrode, it encounters a volume-expanding material in the solid electrolyte and deteriorates the performance, thereby blocking subsequent events in advance. In addition, it is possible to control the battery driving timing by adjusting the location of the volume expansion material and the distance from the Li dendrite growth direction.

Claims (10)

As a solid electrolyte membrane for an all-solid battery,
The solid electrolyte membrane includes an ion conductive solid electrolyte material (a); And lithium or lithium ions are intercalated inorganic particles (b);
The inorganic particles are lithium or lithium ions and physically or chemically reacted to lithiation, and include metals, metal oxides, or both, and are lithified to expand their volume,
The inorganic particles are positioned so as not to directly contact the electrode, the solid electrolyte membrane.
The method of claim 1,
The solid electrolyte membrane includes at least two solid electrolyte layers and at least one volume expansion layer, the volume expansion layer being disposed between the solid electrolyte layers,
The volume expansion layer includes the inorganic particles (B) capable of occluding the lithium or lithium ions, the solid electrolyte membrane.
The method of claim 1,
The inorganic particles (B) have a volume expansion ratio of 10% to 1000% after lithiation compared to before lithiation.
The method of claim 1,
The inorganic particles include Si, Sn, SiO, SnO, MnO ₂ , Fe ₂ O ₃ or two or more of these, a solid electrolyte membrane.
The method of claim 1,
The inorganic particles (B) is 1 to 30% by weight based on 100% by weight of the solid electrolyte membrane, solid electrolyte membrane.
The method of claim 1,
The thickness of the volume expansion layer is 10 nm to 50 ㎛, solid electrolyte membrane.
The method of claim 1,
The ion conductive solid electrolyte material (a) has an ion conductivity of 10 ^-5 S/cm or more, and includes a polymer-based solid electrolyte, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or two or more of them. Electrolyte membrane.
The method of claim 2,
The volume expansion layer is a solid electrolyte membrane containing the inorganic particles in a high concentration.
As an all-solid battery,
The all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between the positive electrode and the negative electrode,
The solid electrolyte membrane is the solid electrolyte membrane according to any one of claims 1 to 8, wherein the all-solid battery.
The method of claim 9,
The solid electrolyte membrane includes a first solid electrolyte layer, a second solid electrolyte layer, and a volume expansion layer, the volume expansion layer being disposed between the solid electrolyte layers,
The volume expansion layer includes the inorganic particles (B) into which the lithium or lithium ions are occluded,
The first solid electrolyte layer faces the negative electrode,
The all-solid-state battery in which the thickness of the first solid electrolyte layer is greater than that of the second solid electrolyte layer.

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