Electrolyte and solid-state battery containing same

Abstract

The present invention relates to an electrolyte and a solid-state battery containing the same. [Solution] The electrolyte comprises a polymer including a PEO (polyethylene oxide)-based polymer containing cross-linkable functional groups; a ceramic compound; and a polar compound, at least a portion of the cross-linkable functional groups forming cross-links to form a three-dimensional network structure of the polymer, and the polar compound is contained within the three-dimensional network structure or is bonded to the polymer chain, and the electrolyte has an activation energy deviation (△Ea) of 0.03 eV or less depending on temperature.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0123075, filed September 15, 2023, and Korean Patent Application No. 10-2024-0123906, filed September 11, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0003] The present invention relates to an electrolyte and a solid-state battery containing the same. [Background technology]

[0004] Lithium-ion batteries that use liquid electrolytes have a structure in which the negative and positive electrodes are separated by a separator, so if the separator is damaged by deformation or external impact, a short circuit can occur, which can lead to risks such as overheating or explosion. Therefore, the development of a solid electrolyte that can ensure safety in the field of lithium-ion secondary batteries is a very important challenge.

[0005] Lithium secondary batteries using solid electrolytes have the advantages of increased battery safety, improved battery reliability due to the ability to prevent electrolyte leakage, and ease of fabrication of thin batteries. Furthermore, lithium metal can be used as the anode, improving energy density. Therefore, they are expected to be used in compact secondary batteries as well as high-capacity secondary batteries for electric vehicles, and are attracting attention as next-generation batteries.

[0006] Among solid electrolytes, polymer solid electrolytes can use ion-conductive polymer materials, and can be used in the form of a composite solid electrolyte in which such polymer materials are mixed with inorganic materials.

[0007] Such conventional hybrid (composite) solid electrolytes are manufactured by dispersing inorganic powders such as oxide ceramics in a polymer matrix, and have the advantages of being more stable against ignition and combustion than existing liquid electrolytes and having higher ionic conductivity than polymer solid electrolytes.

[0008] However, existing composite solid electrolytes have had challenges in that basic prerequisites must be met, such as improving the dispersion of oxide ceramic particles within the polymer matrix and optimizing the physical properties of the polymer matrix used. In particular, when using a highly crystalline polymer such as polyethylene oxide (PEO) as the matrix, it is difficult to produce an electrolyte with improved ionic conductivity. The high crystallinity of the PEO polymer inhibits the chain mobility of the polymer, restricting the movement of lithium ions within the polymer solid electrolyte, limiting the ability to improve the ionic conductivity of the polymer solid electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides an electrolyte in the form of a composite solid electrolyte that exhibits improved ionic conductivity and uniform electrochemical properties at different temperatures.

[0010] The present invention also provides a solid-state battery that includes the electrolyte and exhibits improved ionic conductivity and uniform and excellent operating characteristics over the entire operating temperature range. [Means for solving the problem]

[0011] According to one embodiment of the invention, a polymer including a PEO (polyethylene oxide)-based polymer containing a cross-linkable functional group; a ceramic compound; and a polar compound,

[0012] at least a part of the cross-linking functional groups forms cross-links to form a three-dimensional network structure of the polymer, and the polar compound is contained in the three-dimensional network structure or is bonded to the polymer chain;

[0013] The electrolyte has an activation energy deviation (ΔEa) of 0.03 eV or less according to temperature, as defined by the following Equation 1:

[0014] [Formula 1]

[0015] ΔE a =E a LT -E a HT

[0016] In the above formula 1, E a LT is the activation energy of the electrolyte at -40°C to 10°C, and E a HT is the activation energy of the electrolyte at 10°C to 80°C, and ΔE a indicates the activation energy deviation at each temperature, which is defined as the difference between the two activation energies.

[0017] In such an electrolyte, at least a portion of the polar compound may be dispersed among the polymer chains forming the three-dimensional network structure in a vapor-deposited gaseous state, or may be adsorbed or bonded to the surface or interior of the polymer chains.

[0018] The electrolyte may further include a multifunctional crosslinking agent, and at least some of the crosslinkable functional groups of the PEO-based polymer may form crosslinks with each other via the multifunctional crosslinking agent.

[0019] In a specific example, the polyfunctional crosslinking agent may include a polyfunctional compound having a plurality of curable functional groups selected from the group consisting of a (meth)acrylic functional group, an alkoxy functional group, a peroxide functional group, a vinyl functional group, a hydroxy group, an epoxy functional group, and an allyl group.

[0020] The PEO polymer may contain one or more crosslinkable functional groups, which are bonded to the polymer chain of the PEO polymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (wherein an alkylene linker having 0 carbon atoms represents a single bond), and may be a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

[0021] The electrolyte may further contain the lithium salt, and the lithium salt may be present in the form of at least partially dissociated cations and anions. The cations and / or anions may be present in a state bound to the polymer and may migrate during charging and discharging of the battery. The lithium salt may be present in an amount of 25 to 45 parts by weight per 100 parts by weight of the PEO-based polymer having a cross-linkable functional group.

[0022] In a specific embodiment, the PEO-based polymer of the electrolyte may be a copolymer containing repeating units of the following formulas 1 to 3:

[0023] [Chemical formula 1]

[0024] [ka]

[0025] [Chemical formula 2]

[0026] [ka]

[0027] [Chemical formula 3]

[0028] [ka]

[0029] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, R3 is an alkyl group having 1 to 5 carbon atoms, R2 is a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to the polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), l, m, and n are the number of repeating units, l and n are each independently an integer of 1 to 100,000, and m is an integer of 0 to 100,000.

[0030] Such PEO-based polymers can have a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol.

[0031] The polar compound may include at least one selected from the group consisting of carbonate compounds and sulfonyl compounds, and may be a polar compound derived from a carbonate solvent or a sulfonyl solvent. More specifically, the polar compound may include at least one selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane.

[0032] The polar compound may be contained in an amount of 0.1% by weight or more and less than 10% by weight based on the total weight of the electrolyte.

[0033] The ceramic compound may include an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate, and more specifically, may include one or more oxide-based solid electrolytes selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO) compounds, lithium-silicon titanium phosphate (LSTP) compounds, lithium-lanthanum-titanium oxide (LLTO) compounds, lithium-aluminum-titanium phosphate (LATP) compounds, lithium-aluminum-germanium phosphate (LAGP) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds.

[0034] The ceramic compound may be contained in the form of particles having a diameter of 100 nm to 1000 nm, and may be contained in an amount of 10 to 100 parts by weight per 100 parts by weight of the polymer mixture.

[0035] Meanwhile, according to another embodiment of the present invention, there is provided a solid-state battery including an electrolyte layer containing the electrolyte of the above-described embodiment. [Effects of the Invention]

[0036] An electrolyte according to one embodiment of the invention can exhibit improved ionic conductivity by improving the mobility of polymer chains and uniformly distributing ceramic particles in the electrolyte, while maintaining the original structural characteristics of the polymer without deformation or destruction of the polymer chains.

[0037] Furthermore, the electrolyte may exhibit improved ionic conductivity and mechanical properties by including a trace amount of polar compounds, for example, in a vapor-deposited state.

[0038] In particular, when a polar solvent is incorporated into the electrolyte by vapor deposition, gelation is prevented and the relaxation time of the internal polymer chains is delayed, improving the mobility of the polymer chains, thereby maintaining uniform and excellent lithium ion mobility despite temperature changes.

[0039] Therefore, the electrolyte and solid-state battery can exhibit excellent overall ionic conductivity and electrochemical properties despite changes in operating temperature. [Brief explanation of the drawings]

[0040] [Figure 1] 1 is a graph showing the results of evaluating the activation energy and log(σi) of the electrolytes contained in Example 1 and Comparative Example 1 at different absolute temperatures.

[0041] [Figure 2] 1 is a graph showing the results of a charge-discharge test at room temperature (25° C.) of the solid state battery of Example 1.

[0042] [Figure 3] 1 is a graph showing the results of a charge-discharge test of the solid state battery of Comparative Example 1 at room temperature (25° C.) and at a high temperature (60° C.). DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, specific embodiments of the invention will be described in more detail for better understanding of the invention.

[0044] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention.

[0045] The term "bonded" as used herein may refer to a state in which a polar compound is "bonded" to a polymer chain, for example, a PEO-based polymer chain having cross-linkable functional groups. This "bonding" broadly refers to a state in which a polar compound in a gaseous state is fixed to a polymer chain, for example, by vapor deposition of a polar solvent. The term "bonded" is not limited to a specific physical or chemical bond, but rather includes a state in which the polar compound is fixed by various bonds, including these physical or chemical bonds, a state in which the polar compound is fixed by simple adhesion, such as adsorption, or a state in which the polar compound is included in a three-dimensional network structure formed by cross-linking of the polymer, and is fixed adjacent to the polymer chain or cross-linked structure.

[0046] The term "three-dimensional network structure" as used herein refers to a structure including a three-dimensional frame and an internal space formed by the frame, and the frame may include polymer chains including crosslinks formed by the crosslinking functional groups, for example, crosslinks between crosslinking functional groups and / or crosslinks between the crosslinking functional groups and a crosslinking agent. The three-dimensional network structure may also be referred to as a crosslinked structure.

[0047] As used herein, the term "a gaseous state" for a polar compound (polar solvent) in an electrolyte refers to a state distinct from when the polar solvent or an electrolyte or polar solution containing the polar compound is injected in a liquid state. This refers to the polar compound being deposited in a vapor state and existing in a state distinct from when the polar solvent is injected in a liquid state immediately after the electrolyte is manufactured or during the charge / discharge process of a solid-state battery containing the polar compound. However, depending on the storage or operating conditions of the electrolyte and / or battery, the vapor-deposited polar compound may be locally or temporarily liquefied. In this case, the vapor-deposited polar compound exhibits higher mobility than the polar solvent injected in a liquid state, and therefore is also considered to exist in a "gaseous state."

[0048] In this specification, the term "solid-state battery" may be interpreted to encompass not only so-called all-solid-state batteries that do not contain any liquid in the entire battery structure including the electrolyte (layer), but also batteries that contain a small amount of liquid due to, for example, storage or operating conditions of the electrolyte and / or battery, such as when a polar compound vapor-deposited on the electrolyte is locally or temporarily liquefied.

[0049] Meanwhile, in order to improve the ionic conductivity of solid electrolytes, electrolytes have been prepared by dispersing ceramic compounds such as oxides in a polymer matrix. However, such electrolytes have problems such as uneven distribution of oxide-based ceramic particles in the polymer matrix or reduced ionic conductivity when a highly crystalline polymer such as polyethylene oxide is used as the polymer.

[0050] Therefore, to improve the ionic conductivity of solid electrolytes and enhance the dispersibility of the ceramic compounds, the solid electrolyte has been immersed in or supported by an electrolyte solution or a liquid solvent, or the electrolyte solution or polar solvent has been directly injected into the solid electrolyte in a liquid state. Directly adding a significant amount of electrolyte solution or polar solvent to the solid electrolyte can improve the ionic conductivity of the solid electrolyte to some extent. However, this can impair the excellent safety and stability that can be achieved by using solid electrolytes. Furthermore, the improvement in ionic conductivity achieved by adding the electrolyte solution or polar solvent was insufficient, requiring the injection of a significant amount of polar solvent.

[0051] Furthermore, due to the temperature-dependent characteristics of the electrolyte or polar solvent, such as vapor pressure or viscosity, the mobility and ionic conductivity of lithium ions may vary significantly depending on the temperature, and batteries containing the electrolyte may exhibit significant differences in electrochemical characteristics depending on the temperature, which may cause significant variations in drive characteristics and charge / discharge characteristics of solid-state batteries depending on the temperature.

[0052] In addition, when a liquid electrolyte or polar solvent is directly added or injected into a solid electrolyte in a liquid state, unexpected side reactions between the polymer and the liquid can damage the polymer chain or break bonds within the polymer, causing the structure of the solid electrolyte to collapse and resulting in a decrease in ionic conductivity. Moreover, there is a disadvantage that this ionic conductivity decreases even further at low temperatures, where ionic mobility in the liquid electrolyte decreases.

[0053] Furthermore, when a polar solvent or liquid electrolyte is directly injected into a solid electrolyte, the rapid diffusion of liquid phase molecules into the solid electrolyte can rapidly cause relaxation of polymer chains, accelerating gelation on the surface and resulting in a decrease in mechanical properties. In addition, problems such as leakage of the liquid electrolyte or polar solvent can occur, which can reduce the safety of the battery.

[0054] Therefore, the inventors applied a method of vapor deposition of a polar compound derived from a polar solvent onto an electrolyte containing a polymer cross-linked from a polyethylene oxide (PEO)-based polymer modified with cross-linking functional groups and a ceramic compound. In one embodiment, the electrolyte thus manufactured includes a polymer including a PEO-based polymer containing cross-linking functional groups; a ceramic compound; and a polar compound, wherein at least some of the cross-linking functional groups form cross-links with each other to form a three-dimensional network structure of the polymer, and the polar compound can be included in the three-dimensional network structure or can exhibit a structure bonded to the polymer chain.

[0055] It has been confirmed that such electrolytes exhibit improved ionic conductivity despite containing a small amount of polar compounds derived from a polar solvent. In such electrolytes, the polar compounds can exhibit a different state from that of a polar solvent injected in large amounts as a liquid due to the vapor deposition and small amount of content. For example, the polar compounds may exist at least partially in a gaseous state in the electrolyte and may be locally or temporarily converted to a liquid or gas-liquid coexistence state during battery operation. Furthermore, the polar compounds may be uniformly dispersed within the three-dimensional network structure defined by the cross-linking, or may be bound or attached to the polymer chains between the three-dimensional network.

[0056] The different states of these polar compounds are expected to affect the physical properties of the PEO-based polymer, such as its crystallinity, increasing the chain mobility of the polymer chains and thereby improving the lithium ion conductivity contained in the electrolyte.Furthermore, the electrolyte can exhibit even better ion conductivity due to the ceramic compounds uniformly dispersed within the three-dimensional network structure.

[0057] Furthermore, the electrolyte does not exhibit significant deviations in internal energy and lithium ion mobility despite temperature changes due to the trace amount of polar compound contained and the different state from the polar solvent injected in liquid form. Therefore, the electrolyte of one embodiment may exhibit a temperature-dependent activation energy deviation (ΔEa) of 0.03 eV or less, or 0.005 to 0.025 eV, as defined by the following Equation 1:

[0058] [Formula 1]

[0059] ΔE a =E a LT -E a HT

[0060] In the above formula 1, E a LT is the activation energy of the electrolyte at -40°C to 10°C, and E a HT is the activation energy of the electrolyte at 10°C to 80°C, and ΔE a indicates the activation energy deviation at each temperature, which is defined as the difference between the two activation energies.

[0061] In this case, the activation energy deviation can be calculated from the ionic conductivity of the electrolyte measured at each absolute temperature. More specifically, the ionic conductivity (σ i Based on the measurement results of log(σ i ) and 1000 / T (T is the absolute temperature at which the ionic conductivity is measured) can be fitted to the Arrhenius equation in the following equation 3 to derive the activation energy Ea corresponding to the slope, and then E in the above equation 1 can be calculated. a LT , E a HT and ΔE a can be calculated respectively.

[0062] [Formula 3]

[0063]

number

[0064] In the above formula, σ i、0 denotes the maximum ionic conductivity of the electrolyte, and σ i denotes the ionic conductivity of the electrolyte measured at absolute temperature T, Ea denotes the activation energy of the electrolyte at absolute temperature T, and R denotes the gas constant.

[0065] From such a low deviation in activation energy, it can be seen that the above-described electrolyte and a solid-state battery including the same exhibit excellent ionic conductivity and electrochemical properties without significant deviation despite changes in temperature.

[0066] As will be seen in the examples below, these characteristics can only be achieved with an electrolyte in which a polar compound is vapor-deposited, and cannot be achieved with a composite solid electrolyte that does not contain the polar compound or that has a significant amount of polar solvent (liquid polar compound) injected in. It has been confirmed that such existing composite solid electrolytes have large deviations in activation energy with respect to temperature, and that solid-state batteries containing them have large deviations in charge / discharge characteristics with respect to temperature.

[0067] Meanwhile, in the electrolyte of the embodiment, the polar compound may be dispersed among the polymer chains forming the three-dimensional network structure in a vapor-deposited gaseous state, or may be adsorbed or bound to the surface or interior of the polymer chains.

[0068] Such electrolytes include polar compounds incorporated or bonded in a small amount into a three-dimensional network structure by vapor deposition, as described below. Such polar compounds have a different state from a polar solvent that is injected into the electrolyte in a large amount in a liquid state. The state of such polar compounds can be confirmed, for example, by separating an electrolyte layer containing the polar compounds from a solid-state battery at a temperature lower than the boiling point of the polar compounds and observing the layer with the naked eye or an electron microscope. If no liquid component is observed on the surface of the electrolyte layer under such observation, the electrolyte is considered to be in a state similar to that of an embodiment in which the polar compounds are vapor-deposited.

[0069] In contrast, when a liquid polar solvent or electrolyte solution is injected into the electrolyte, a liquid component or a component exhibiting wettability can be observed on the surface of the electrolyte layer. Furthermore, as confirmed by the examples described below, an electrolyte in which the polar compound is vapor-deposited exhibits improved ionic conductivity despite a lower polar compound content compared to when a liquid polar solvent or electrolyte solution is injected. Comparison of ionic conductivities also confirms that the polar compound is vapor-deposited and contained in a gaseous state.

[0070] In the electrolyte of the embodiment, the polar compound may be contained in an amount of 0.1 wt % or more and less than 10 wt % based on the total weight of the electrolyte. For example, the content of the polar compound may be 0.1 wt % or more, 0.5 wt % or more, 1 wt % or more, 2 wt % or more, or 3 wt % or more, or 4 wt % or less, 5 wt % or less, 6 wt % or less, 7 wt % or less, 8 wt % or less, 9 wt % or less, or less than 10 wt %.

[0071] If the polar compound content is less than 0.1 wt%, it is difficult to induce changes in chain conformation within the polymer, and the ionic conductivity of the electrolyte is unlikely to be sufficiently improved despite vapor deposition of the polar compound. Conversely, if the polar compound content is 10 wt% or more, the electrolyte exhibits the same state as a polar solvent injected in liquid form, making it difficult to achieve the effects of vapor deposition. As a result, the electrolyte contains a large amount of polar solvent or electrolyte solution that is essentially always in liquid form, resulting in the characteristics of a semi-solid battery. This can lead to a decrease in the mechanical strength of the electrolyte due to gelation of the polymer, and the ionic conductivity of the electrolyte can also be insufficient.

[0072] The content of the polar compound can be calculated by measuring the content of the polar compound evaporated while heating the electrolyte. Specifically, taking into account the boiling point and vapor pressure of the polar compound at each temperature, the polar compound can be heated at a temperature at which the polar compound begins to evaporate, for example, 40°C or higher or 50°C or higher, to the boiling point or a temperature 10°C above the boiling point, collecting the liquid phase of the polar compound evaporated within the temperature range, and measuring the weight of the liquid phase. The calculation can be stopped when the measured amount reaches saturation (e.g., when the measured amount no longer increases) as the heating time at the elevated temperature elapses, and this is considered to be the total amount of polar compound contained in the electrolyte.

[0073] In addition, the content of the polar compound contained in the electrolyte can be adjusted by the amount of polar compound used in the vapor deposition step described below and / or the conditions of the vapor deposition, such as the vapor deposition time and temperature, as will be apparent from the examples described below.

[0074] Meanwhile, in the electrolyte of one embodiment, the cross-linkable functional group may be directly bonded to the main chain of the PEO-based polymer, or may be bonded via an alkylene or alkylene oxide linker. Therefore, the cross-linkable functional group may be bonded via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), and may be one or more groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

[0075] In one embodiment of the present invention, the cross-linking functional groups may be of two or more types. The cross-linking functional groups may be the same or different. When the cross-linking functional groups are different, multiple types of repeating units each containing these functional groups may be included. In addition, when multiple types of cross-linking functional groups are included, it may be easier to control the mobility and ionic conductivity of the polymer chain.

[0076] The cross-linkable functional group refers to a functional group that can form a cross-link with another functional group via a cross-linking agent, and can be bonded to a polymer chain in the form of a side chain.

[0077] In a more specific embodiment, the PEO-based polymer having a cross-linking functional group may be a copolymer having repeating units of the following chemical formulas 1 to 3:

[0078] [Chemical formula 1]

[0079] [ka]

[0080] [Chemical formula 2]

[0081] [ka]

[0082] [Chemical formula 3]

[0083] [ka]

[0084] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, and R3 represents an alkyl group having 1 to 5 carbon atoms;

[0085] R2 represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond);

[0086] l, m, and n are the repeat numbers of the repeat unit, l and n are each independently an integer of 1 to 100,000, or 50 to 80,000, or 100 to 50,000, and m is an integer of 0 to 100,000, or 50 to 80,000, or 100 to 50,000.

[0087] For example, the cross-linkable functional group of R2 may form a matrix polymer having a three-dimensional network structure formed by the cross-linking. The formation of the three-dimensional network structure by the cross-linking may improve the mechanical properties of the electrolyte. In one embodiment, the polar compound may be contained or bound within the three-dimensional network structure, thereby providing an electrolyte having improved ionic conductivity.

[0088] It is also clear that the PEO-based polymer may contain two or more repeating units of Chemical Formula 3, in which R2 is a different cross-linking functional group, and may also contain one or more repeating units of Chemical Formula 2.

[0089] If l, m, and n are each too small, the molecular weight is too small to form a polymer, and if l, m, and n are each too large, the viscosity increases, reducing solubility during preparation of a polymer solution, making it difficult to form the polymer for electrolyte preparation. In particular, if the number of repeating units containing cross-linking functional groups among l, m, and n is too large, the degree of cross-linking increases excessively, reducing the mobility of polymer chains and decreasing ionic conductivity.

[0090] As used herein, a "hydroxy group" refers to an --OH group.

[0091] As used herein, a "carboxyl group" refers to a -COOH group.

[0092] As used herein, an "isocyanate group" refers to a -N=C=O group.

[0093] As used herein, a "nitro group" refers to the -NO2 group.

[0094] As used herein, a "cyano group" refers to a -CN group.

[0095] As used herein, an "amide group" refers to -C(=O)NR'R", where R' and R" can each independently be hydrogen or a C1-C5 alkyl group, or R' and R" together with the N atom to which they are attached can form a heterocycle having C4-C8 atoms in the ring structure.

[0096] In this specification, the term "amine group" can be selected from the group consisting of monoalkylamine groups, monoarylamine groups, monoheteroarylamine groups, dialkylamine groups, diarylamine groups, diheteroarylamine groups, alkylarylamine groups, alkylheteroarylamine groups, and arylheteroarylamine groups. The number of carbon atoms is not particularly limited, but preferably ranges from 1 to 30. Specific examples of the amine group include, but are not limited to, methylamine groups, dimethylamine groups, ethylamine groups, diethylamine groups, phenylamine groups, naphthylamine groups, biphenylamine groups, dibiphenylamine groups, anthracenylamine groups, 9-methylanthracenylamine groups, diphenylamine groups, phenylnaphthylamine groups, ditolylamine groups, phenyltolylamine groups, triphenylamine groups, biphenylnaphthylamine groups, phenylbiphenylamine groups, biphenylfluorenylamine groups, phenyltriphenylenylamine groups, and biphenyltriphenylenylamine groups. Furthermore, the term "amino group" refers to -NH.

[0097] As used herein, an "allyl group" refers to the group -CH2-CH=CH2.

[0098] The weight-average molecular weight (Mw) of the polymers containing Formulas 1 to 3 may be 100,000 g / mol to 4,000,000 g / mol, specifically, 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, or 3,000,000 g / mol or less, or 2,000,000 g / mol or less. If the weight-average molecular weight (Mw) of the polymer is too small, the mechanical properties of the resulting electrolyte may not be satisfactory. If the weight-average molecular weight (Mw) of the polymer is too large, the viscosity may increase, reducing solubility during the preparation of the polymer solution and making molding for electrolyte preparation difficult. Furthermore, the ionic conductivity of the electrolyte may decrease due to increased crystallinity and reduced chain mobility within the electrolyte.

[0099] In particular, if the number of repeating units of Formula 3 containing cross-linking functional groups among l, m, and n is too large, the degree of cross-linking may increase excessively, reducing the mobility of polymer chains and decreasing the ionic conductivity of the electrolyte.

[0100] The polymer may also be a random polymer or a block copolymer.

[0101] Meanwhile, in a specific embodiment of the present invention, the polar compound may be contained on or bonded to the surface or inside of the polymer chains by vapor deposition, for example, in a substantially gaseous state (including a local, temporary liquid state). Specifically, the polar compound may be diffused or dispersed among the polymer chains that form a three-dimensional network structure by crosslinking the crosslinkable PEO-based polymer, or may be adsorbed or bonded to the surface or inside of the polymer chains.

[0102] The polar compound may be a gas molecule of a polar solvent used in the vapor deposition process, and may be adsorbed onto the polymer during vapor deposition and then diffused into the polymer chains, thereby binding to the polymer chains or being dispersed or diffused in the internal space between the polymer chains. By binding the polar compound to the polymer chains or being dispersed in the internal space between the polymer chains, the ionic conductivity of the final electrolyte may be improved despite its low content, and the characteristics of Formula 1 above may be satisfied, thereby exhibiting uniform electrochemical properties at different temperatures.

[0103] Specifically, polar compounds bound to or contained between the polymer chains can act as plasticizers to plasticize the polymer. The plasticized polymer increases the amorphous region inside, improving the mobility of the polymer chains. The increased mobility of the polymer chains increases the ion hopping effect inside the polymer, improving the ionic conductivity of the electrolyte.

[0104] In addition, the polar compound can act as an intermediate for smooth ion transport through ion hopping. Because the affinity between lithium ions and polar compounds is stronger than the affinity between lithium ions and the ether oxygen of the PEO-based polymer, lithium ions can be transported more quickly and easily within the polymer with the polar compound adsorbed. In other words, as the polar compound flows into the polymer, the cation solvation effect of lithium ions increases, improving ion mobility and, therefore, the ionic conductivity of the electrolyte.

[0105] The polar compound may include at least one compound selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0106] Specifically, the polar compound may include one or more compounds selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane, or a combination thereof.

[0107] As described above, the content of the polar compound can be 0.1% by weight or more and less than 10% by weight based on the total weight of the electrolyte.

[0108] In one embodiment of the present invention, the electrolyte may further include a cross-linking agent in the above-mentioned ratio, and may include cross-linking bonds between the cross-linking agent and the cross-linking functional groups. For example, at least some of the cross-linking functional groups may form cross-links with each other via the cross-linking agent to form the above-mentioned three-dimensional network structure.

[0109] At this time, a crosslinking bond may be formed between the crosslinking agent and the crosslinkable functional group, and the crosslinking bond may be a hydrogen bond, a bond due to Lewis acid-base interaction, an ionic bond, a coordinate bond, or a bond formed by radical polymerization.

[0110] The crosslinking agent is not particularly limited as long as it is a polyfunctional crosslinking agent containing a plurality of curable functional groups capable of forming crosslinks with the crosslinkable functional groups. For example, the crosslinking agent can be one or more selected from the group consisting of a (meth)acrylic functional group, an alkoxy functional group, a peroxide functional group, a vinyl functional group, a hydroxy group, an epoxy functional group, and an allyl group.

[0111] In a more specific example, the crosslinking agent is selected from the group consisting of trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol dimethylacrylate (hereinafter referred to as "EGDMA"), 1,3-diisopropenylbenzene (DIP), 1,4-diacryloyl piperazine, 2-(diethylamino)ethyl methacrylate, 2,6-bisacryloylamidopyridine, 3-(acryloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acrylamido)benzoic acid (3,5-bis(acryloylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methylacryloxypropyltrimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene, ethylene glycol maleic rosinate acrylate, glycidyl methacrylate, hydroxyquinoline, iphenyldiethoxysilane, maleic rosin glycol acrylate, methylene bisacrylamide, N,N'-1,4-phenylenediacrylamine, N,O-bisacryloyl-phenylalaninol, N,O-bismethacryloylethanolamineThe crosslinking agent may be one or more polyfunctional crosslinkers, for example, difunctional or higher compounds, selected from the group consisting of 0-bismethacryloyl ethanolamine, pentaerythritol triacrylate, phenyltrimethoxysilane, tetramethoxysilane, tetramethylene, tetraethoxysilane, and triallyl isocyanurate.

[0112] The crosslinking agent may be included in an amount such that its weight ratio relative to the weight of the PEO-based polymer containing crosslinkable functional groups is 0.07 to 0.19, 0.07 to 0.18, 0.08 to 0.15, or 0.08 to 0.13. If the weight ratio of the crosslinking agent is too small, the formation of a three-dimensional network structure may be hindered, making vapor deposition difficult, resulting in a significant decrease in the ionic conductivity of the electrolyte. Conversely, if the weight ratio of the crosslinking agent is too large, excessive crosslinking and three-dimensional network structure may be formed, reducing the mobility of the polymer chains and thereby decreasing the ionic conductivity.

[0113] Meanwhile, in one embodiment of the present invention, the electrolyte may further include a lithium salt. The lithium salt may be present in the internal space between the polymer chains in a dissociated ionic state, thereby improving the ionic conductivity of the electrolyte. At least a portion of the cations and / or anions dissociated from the lithium salt may be present in a state bound to the polymer chains, thereby exhibiting mobility during charge and discharge of the battery.

[0114] The lithium salts include (CF3SO2)2NLi (Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0115] The lithium salt may be contained in an amount of 25 to 45 parts by weight relative to 100 parts by weight of the PEO-based polymer having a cross-linkable functional group, specifically, 25 parts by weight or more, 30 parts by weight or more, or 35 parts by weight or more, or 40 parts by weight or less, or 45 parts by weight or less. If the content of the lithium salt is less than 25 parts by weight, the ionic conductivity of the electrolyte may decrease, and if it exceeds 45 parts by weight, the mechanical strength may decrease.

[0116] The electrolyte may include a ceramic compound having lithium ion transport ability for improving the conductivity of lithium ions, preferably containing lithium atoms but having the function of transporting lithium ions without storing lithium, thereby improving the ionic conductivity of the electrolyte.

[0117] In addition, the ceramic compound may be included in a state of being uniformly dispersed among the cross-linked polymer chains, for example, within the three-dimensional network structure. The ceramic compound may be added during the cross-linking process and be uniformly dispersed without clumps among the polymer chains formed by the cross-linking. Such a uniformly dispersed ceramic compound may be advantageous for improving the mechanical strength and ionic conductivity of the electrolyte.

[0118] The ceramic compound may also be particulate. Due to its morphological characteristics, the ceramic compound may be contained in a more uniformly dispersed state within the electrolyte. The ceramic compound particles may be spherical, and their diameter may be 100 nm to 1000 nm. If the diameter is less than 100 nm, the amorphization effect due to reduced crystallinity of the polymer is minimal, while if the diameter is more than 1000 nm, the dispersibility may be reduced due to increased aggregation between particles, making it difficult to disperse uniformly.

[0119] The ceramic compound may be an oxide-based or phosphate-based compound, and may be an oxide-based solid electrolyte in the form of, for example, lithium metal oxide or lithium metal phosphate. More specifically, the ceramic compound may be a garnet-type lithium-lanthanum-zirconium oxide (LLZO, Li7La3Zr2O 12 ) compounds, perovskite-type lithium-lanthanum-titanium oxides (LLTO, Li3xLa 2 / 3-x TiO3) compounds, phosphate-based NASICON-type lithium-aluminum-titanium phosphate (LATP, Li 1+x Al x Ti 2-x (PO4)3) compounds, lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5The solid electrolyte may be at least one selected from the group consisting of lithium-lanthanum-zirconium-titanium oxide (LLZTO), lithium-silicon-titanium phosphate (LSTP, LiSiOTiO(PO)), lithium-lanthanum-zirconium-titanium oxide (LLZTO), lithium-aluminum-titanium phosphate (LATP), lithium-aluminum-germanium phosphate (LAGP), and lithium-lanthanum-zirconium-titanium oxide (LLZTO).

[0120] The oxide-based or phosphate-based oxide-based solid electrolyte generally has a maximum resistance of 10 -4 ~10 -3 It has an ionic conductivity of 100 S / cm, is stable in the high voltage range, is stable in air, and has the advantages of being easy to synthesize and handle.

[0121] Therefore, the above-mentioned electrolyte may further contain the electrolyte by mixing the ceramic compound, thereby making it possible to overcome the drawbacks of the polymer-based solid electrolyte.

[0122] In addition, the ceramic compound has high high-temperature stability because it does not easily burn or ignite even at high temperatures of 400° C. or higher. Therefore, when the electrolyte contains the ceramic compound, it is possible to improve the mechanical strength of the electrolyte as well as the high-temperature stability and ionic conductivity.

[0123] The ceramic compound may be contained in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, relative to 100 parts by weight of the PEO-based polymer containing a cross-linkable functional group.

[0124] If the ceramic compound is contained in an excessively small amount, the polymer crystallinity and amorphous effect of the ceramic compound are reduced, resulting in a small increase in the ionic conductivity of the electrolyte, and the mechanical properties may not reach the expected level due to the formation of a composite.

[0125] If the ceramic compound is contained in an excessively large amount, the ceramic compound may not be uniformly dispersed in the polymer, and the ceramic compound particles may aggregate and clump together, resulting in an electrolyte with reduced ionic conductivity.

[0126] On the other hand, the above-mentioned electrolytes can exhibit excellent ionic conductivity, for example, ionic conductivity measured at room temperature of about 25° C. of 0.6 mS / cm or more, 0.95 mS / cm or more, 1.0 mS / cm or more, or 1.0 mS / cm to 3.0 mS / cm.

[0127] Such ionic conductivity can be calculated from the resistance (Ω) of the electrolyte measured by an electrochemical impedance spectrometer at a constant temperature using the following equation 2:

[0128] [Formula 2]

[0129]

number

[0130] In the above formula 2, σ i is the ionic conductivity of the electrolyte (S / cm), R is the resistance of the electrolyte (Ω) measured by the electrochemical impedance spectrometer, L is the thickness of the electrolyte (μm), and A is the area of ​​the electrolyte (cm 2 ) means

[0131] Electrolyte manufacturing method

[0132] The method for manufacturing the electrolyte may include the steps of: mixing a PEO-based polymer having a cross-linkable functional group with a ceramic compound; and then performing a cross-linking reaction in the presence of a cross-linking agent in a predetermined ratio relative to the PEO-based polymer contained in the mixture; and vapor depositing a polar solvent on the cross-linked resultant.

[0133] The PEO-based polymer containing the crosslinkable functional group has been described above.

[0134] Each stage will be explained in more detail below.

[0135] First, a PEO (polyethylene oxide) polymer containing a cross-linkable functional group is mixed with a ceramic compound, and then a cross-linking reaction is carried out in the presence of a cross-linking agent in a certain ratio relative to the PEO polymer contained in the mixture, thereby producing a polymer having the above-mentioned three-dimensional network structure.

[0136] Such crosslinking reactions can be carried out in the presence of a crosslinking agent and an initiator in a certain ratio as described above.

[0137] In addition, a lithium salt may be added together in the mixing step and / or the crosslinking reaction step to form an electrolyte.

[0138] The ceramic compound can be the same as that used in the electrolyte described above, and the content can also be the same.

[0139] The crosslinking reaction may occur during the drying process after a solution containing the PEO-based polymer and the ceramic compound is applied to a substrate to form a coating film.

[0140] Specifically, the mixed solution can be prepared by mixing the PEO-based polymer and ceramic compound in a solvent, and additionally mixing a crosslinker, initiator, and / or lithium salt together. Alternatively, a solution containing the PEO-based polymer, crosslinker, initiator, and / or lithium salt can be prepared first, and then the ceramic compound can be added to prepare a mixed solution or suspension.

[0141] The solvent is not particularly limited as long as it can be mixed with the PEO-based polymer, crosslinker, initiator, and / or lithium salt and can be easily removed by a drying process. For example, the solvent may be acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), or N,N-dimethyl formamide (DMF). Such solvents serve as reaction media for crosslinking and are distinct from polar solvents contained in liquid electrolytes, etc., and are completely removed by drying after crosslinking.

[0142] The concentration of the mixed solution can be appropriately adjusted taking into consideration the smooth progress of the molding process for producing the electrolyte. Specifically, the concentration of the polymer solution may refer to the concentration (w / w%) of the polymer in the polymer solution. The concentration of the polymer may refer to the concentration of the PEO-based polymer. For example, the concentration of the polymer solution may be 5 wt% to 20 wt%, specifically, 5 wt% or more, 7 wt% or more, or 9 wt% or more, or 13 wt% or less, 17 wt% or less, or 20 wt% or less. If the concentration of the polymer solution is less than 5 wt%, the concentration may be too low, resulting in a decrease in the mechanical strength of the electrolyte or in the electrolyte running off when applied to a substrate. If the concentration exceeds 20 wt%, it may be difficult to dissolve the lithium salt in the polymer solution to the desired concentration, or the viscosity may be high, resulting in a decrease in solubility or difficulty in applying the solution to a uniform thin film.

[0143] The substrate is not particularly limited as long as it serves as a support for the coating film. For example, the substrate may be SUS (stainless steel), a polyethylene terephthalate film, a polytetrafluoroethylene film, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a vinyl chloride copolymer film, a polyurethane film, an ethylene-vinyl acetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film.

[0144] The coating method is not particularly limited as long as it can coat the polymer solution on the substrate to form a coating film, and may be, for example, bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting.

[0145] The coating film formed on the substrate by this coating method can be formed into a film-type polymer by a drying process, from which the residual solvent has been completely removed. The drying process can be divided into a primary drying process and a secondary drying process to prevent shrinkage of the polymer due to rapid evaporation of the solvent. The primary drying process can remove a portion of the solvent by drying at room temperature, and the secondary drying process can completely remove the solvent by high-temperature drying in a vacuum. The high-temperature drying can be performed at a temperature of 80°C to 130°C. If the high-temperature drying temperature is less than 80°C, the residual solvent cannot be completely removed, and if it exceeds 130°C, the polymer will shrink, making it difficult to form a uniform electrolyte membrane.

[0146] The crosslinking agent may form a bond with the crosslinkable functional group. The types of the crosslinking agent, the content (weight ratio) of the crosslinking agent, and the type of bond with the crosslinkable functional group are as described above.

[0147] The initiator can induce a radical polymerization reaction between the cross-linkable functional groups to form cross-links between the cross-linkable functional groups. The functional group that enables the radical polymerization reaction may be a functional group containing vinyl at its terminal, or may be, for example, an allyl group.

[0148] The initiator is not particularly limited as long as it is an initiator that can induce a radical polymerization reaction between the cross-linking functional groups. For example, the initiator may include one or more selected from the group consisting of benzoyl peroxide, azobisisobutyronitrile, lauroyl peroxide, cumene hydroperoxide, diisopropylphenyl hydroperoxide, tert-butyl hydroperoxide, paramethane hydroperoxide (p-methyl hydroperoxide), and 2,2'-azobis(2-methylpropionitrile).

[0149] The initiator can be used in an amount of 0.5 to 2 parts by weight based on 100 parts by weight of the PEO-based polymer containing cross-linking functional groups, and when used in this range, it can induce a radical polymerization reaction between the cross-linking functional groups to efficiently form cross-links.

[0150] The content and type of the lithium salt are as described above.

[0151] In the vapor deposition step, the crosslinked resultant can be vapor-deposited by exposing it to a vaporized polar compound (polar solvent).

[0152] Specifically, the vapor deposition can be performed by heating the polar solvent at a temperature equal to or higher than room temperature, contacting the vapor of the polar compound obtained with the crosslinked product, and allowing it to penetrate inside. Through such vapor deposition, the polar compound, for example, in a gaseous state, can be uniformly diffused on the surface and / or inside of the polymer, and the polar compound gas molecules can be bound to the polymer chains or can be contained in the internal space of the polymer chains in a uniformly dispersed or diffused form.

[0153] When the polar solvent is placed at room temperature during vapor deposition, a small amount of the polar solvent with a low boiling point gradually vaporizes at room temperature and penetrates into the polymer, effectively inducing a conformational change in the cross-linked polymer chains within the polymer.

[0154] Furthermore, the vapor deposition rate can be increased by heating the polar solvent during the vapor deposition. The heating temperature is not particularly limited as long as it is a temperature at which the polar solvent can change phase to vapor, and may be, for example, 30°C to 80°C. While typical PEO melts at 60°C, the PEO copolymer modified with cross-linking functional groups exhibits improved heat resistance and can withstand temperatures up to 80°C when a cross-linked structure is formed, thereby further increasing the vapor deposition rate. The heating method is not limited as long as it can provide energy to generate vapor. Examples of suitable methods include, but are not limited to, direct heating using a burner or fan, or indirect heating using a heater or steam tube.

[0155] If the heating temperature is too high, the polar solvent may boil above its boiling point, the solvent may undergo structural changes, or polymer deformation may occur. In addition, it is difficult to control the evaporation rate of the polar solvent during vapor deposition. Therefore, in order to vapor deposit a small amount of polar solvent, it is preferable to perform vapor deposition at a heating temperature within the appropriate range as defined above.

[0156] Meanwhile, the content of the polar compound in the final electrolyte can be controlled by adjusting the vapor deposition temperature, heating rate, amount of polar solvent (polar compound) used for evaporation during vapor deposition, and vapor deposition time and rate, as will be apparent from the following examples.

[0157] solid state battery

[0158] An additional embodiment of the invention also relates to a solid-state battery including the electrolyte, the solid-state battery including a negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode, the electrolyte being according to one of the embodiments described above.

[0159] Specifically, the electrolyte contains a polymer in which a PEO (polyethylene oxide)-based polymer containing a cross-linkable functional group is cross-linked via a cross-linking agent, and a polar compound, and the ceramic compound is uniformly dispersed, improving ionic conductivity, making it suitable as an electrolyte for solid-state batteries.

[0160] Meanwhile, the positive electrode included in the solid-state battery may include a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of a positive electrode current collector.

[0161] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0162] The positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and examples thereof include lithium cobalt oxide, lithium nickel oxide, Li[NixCoyMnzMv]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, and x+y+z+v=1), Li(LiaMb-a-b'M'b')O 2-c A c(wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2; M includes Mn and one or more elements selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more elements selected from the group consisting of Al, Mg, and B; and A is one or more elements selected from the group consisting of P, F, S, and N); layered compounds and compounds substituted with one or more transition metals, such as those represented by the formula Li 1+y Mn 2-y Lithium manganese oxides such as LiMnO4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-y Ni-site lithium nickel oxide represented by MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-y M y Examples of such compounds include, but are not limited to, lithium manganese composite oxides expressed as Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0163] The positive electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40 wt % or more, or 50 wt % or more, or 70 wt % or less, or 80 wt % or less. If the content of the positive electrode active material is less than 40 wt %, the connectivity between the positive electrode active materials and the electrical properties may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be high.

[0164] The binder is a component that aids in bonding the positive electrode active material to the conductive material and the current collector, and is selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, and polyacrylonite. The binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0165] The binder may be contained in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1 wt % or more or 3 wt % or more, and 15 wt % or less or 30 wt % or less. If the binder content is less than 1 wt %, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced. If the binder content exceeds 30 wt %, the adhesive strength may be improved, but the content of the positive electrode active material may be reduced accordingly, resulting in a reduced battery capacity.

[0166] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the solid-state battery, has excellent electrical conductivity without inducing chemical changes in the battery, and is typically graphite or conductive carbon. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials having a graphene or graphite crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more, but are not necessarily limited thereto.

[0167] The conductive material may typically be included in an amount of 0.5 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5 wt % or more, or 1 wt % or more, or 20 wt % or less, or 30 wt % or less. If the content of the conductive material is too low, such as less than 0.5 wt %, it may be difficult to expect an improvement in electrical conductivity, or the electrochemical characteristics of the battery may be degraded. If the content of the conductive material is too high, such as more than 30 wt %, the amount of positive electrode active material may be relatively small, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the positive electrode is not particularly limited, and conventional methods known in the art, such as coating the positive electrode active material, may be used.

[0168] The positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between an external conductor and the positive electrode active material layer.

[0169] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without inducing chemical changes in the solid-state battery, and examples of the positive electrode current collector include copper, stainless steel, aluminum, nickel, titanium, palladium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, silver, or the like, and aluminum-cadmium alloys.

[0170] The positive electrode current collector may have a micro-irregular structure or a three-dimensional porous structure on its surface to strengthen the bonding strength with the positive electrode active material layer, and may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or nonwoven fabric.

[0171] Such a positive electrode can be manufactured by a conventional method. Specifically, the positive electrode active material, conductive material, and binder are mixed in an organic solvent to form a positive electrode active material layer. The resulting composition is then applied to a positive electrode current collector, dried, and optionally, compressed into a current collector to improve electrode density. Preferably, the organic solvent is one that can uniformly disperse the positive electrode active material, binder, and conductive material and is easily evaporated. Specific examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP).

[0172] Meanwhile, the negative electrode included in the solid-state battery may include a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0173] The negative electrode active material may include a material capable of reversibly intercalating or deintercalating lithium (Li+), a material capable of reversibly forming a lithium-containing compound by reacting with lithium ions, lithium metal, or a lithium alloy.

[0174] The material capable of reversibly inserting or extracting lithium ions (Li+) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material capable of reacting with lithium ions (Li+) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0175] Preferably, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0176] The negative electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt % or more or 50 wt % or more, or 70 wt % or less or 80 wt % or less. If the content of the negative electrode active material is less than 40 wt %, the electrical properties may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be high.

[0177] The binder is the same as that described above in the positive electrode active material layer.

[0178] The conductive material is the same as that described above in the positive electrode active material layer.

[0179] The negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery, and examples of the negative electrode current collector that can be used include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. As with the positive electrode current collector, the negative electrode current collector can be in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc., with a finely textured surface.

[0180] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode may be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the art, such as compression bonding, coating, deposition, etc. Furthermore, the negative electrode of the present invention also includes a case where a thin metallic lithium film is formed on a metal plate by initial charging after a battery is assembled without a thin lithium film on the negative electrode current collector.

[0181] Meanwhile, according to additional embodiments of the present invention, there are provided a battery module including the solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

[0182] Specific examples of the device include, but are not limited to, power tools powered by a battery-powered motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0183] Hereinafter, preferred examples will be presented for the understanding of the invention. However, the following examples are provided merely to facilitate understanding of the invention, and the invention is not limited thereto.

[0184] Example

[0185] Example 1: Electrolyte and solid-state battery fabrication

[0186] Step 1) Preparation of polymers including copolymers

[0187] A polyethylene oxide (PEO)-based copolymer of the following formula 1a was prepared:

[0188] [Chemical formula 1a]

[0189] [ka]

[0190] In the above chemical formula 1a, R1 is -CH2-O-(CH2-CH2-O) k R2 was -CH2-O-CH2-CH=CH2, k was 2, the l:m:n ratio was 85:13:2, and the weight average molecular weight (Mw) of the copolymer was about 2,000,000 g / mol.

[0191] The copolymer of formula 1a has an allyl group linked via a methylene oxide linker as a cross-linking functional group.

[0192] The polyethylene oxide copolymer was mixed with trimethylolpropane trimethacrylate as a crosslinker, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound in acetonitrile as a solvent to prepare a mixed solution of the polymer and the ceramic compound, which was then stirred for 24 hours using a magnetic bar. The mixed solution of the polyethylene oxide copolymer and the ceramic compound was prepared by mixing 100 parts by weight of the polyethylene oxide copolymer with 20 parts by weight of trimethylolpropane trimethacrylate as a crosslinker, 1 part by weight of benzoyl peroxide as an initiator, 36 parts by weight of LiTFSI as a lithium salt, and 40 parts by weight of LSTP as a ceramic compound. The concentration of the polyethylene oxide copolymer polymer in the mixed solution was 11.1 wt%, and the concentrations of the polyethylene oxide copolymer polymer and the ceramic compound were 14.9 wt% using acetonitrile as a solvent.

[0193] The prepared mixed solution was solution-cast on the lower substrate of a coin cell, and then primarily dried at room temperature for 12 hours, and then secondary dried in a vacuum oven at 100°C for 12 hours to prepare an electrolyte film with a thickness of 200 μm.

[0194] Step 2) Electrolyte production

[0195] The polymer was attached to the upper plate of a chamber, and the lower part of the chamber was filled with 50 μL of ethyl methyl carbonate (EMC) solvent. The solvent was allowed to evaporate naturally at room temperature for 72 hours, and EMC vapor was introduced into the polymer attached to the upper part of the chamber to deposit it on the polymer, producing an electrolyte.

[0196] Step 3) Manufacturing solid-state batteries (electrode assemblies)

[0197] NCMA(LiNi 0.85 Co 0.05 Mn 0.08 Al 0.02O2) Cathode active material particles (particle size: 5-10 μm, LG CHEM, Republic of Korea), superconductive carbon (C-65), cross-linked PEO copolymer of Formula 1a used in the first step, and LiTFSI were mixed in a weight ratio of 77.6:3:14.2:5.2 with acetonitrile as the solvent and stirred at room temperature for 3 minutes at 1500 rpm using a paste mixer. The resulting mixture was cast onto aluminum foil and dried for 6 hours at room temperature, followed by secondary drying at 100°C for 12 hours to prepare a 60 μm-thick cathode film. The cathode film had a concentration of 6.712 mg / cm. 2 After punching out by mass loading, the composite solid electrolyte produced above was used as an electrolyte film, and lithium metal foil (300 μm) was used as the negative electrode, and these were laminated in a sandwich type to produce a coin cell.

[0198] Example 2: Electrolyte and solid-state battery fabrication

[0199] In step 2) of Example 1, the polymer was attached to the upper plate of a chamber, and 300 μL of ethyl methyl carbonate (EMC) solvent was filled in the lower part of the chamber and allowed to evaporate naturally at room temperature for 72 hours. EMC vapor was then introduced into the polymer attached to the upper part of the chamber to deposit it on the polymer, thereby preparing an electrolyte.

[0200] The remaining steps were carried out in the same manner as in Example 1 to prepare an electrolyte and a solid-state battery.

[0201] Comparative Example:

[0202] Comparative Example 1: Electrolyte and Solid-State Battery Fabrication

[0203] An electrolyte and a solid-state battery were fabricated in the same manner as in Example 1, except that the step of vapor-depositing the EMC solvent (step 2) in Example 1 was omitted.

[0204] Comparative Example 2: Electrolyte and Battery Production (Containing Large Amounts of Polar Solvent)

[0205] An electrolyte was prepared in the same manner as in Example 1, except that in step 2 of Example 1, the EMC solvent was not vapor-deposited but was directly injected as a liquid solvent. The EMC solvent was directly injected so that the content of the EMC solvent was 12 wt % based on the total weight of the prepared electrolyte.

[0206] The remaining steps were carried out in the same manner as in Example 1 to prepare the electrolyte and the battery.

[0207] Experimental Example

[0208] Experimental Example 1: Measurement of polar compound content

[0209] The polar compound content can be measured by monitoring the weight of the liquid phase evaporated over time while heating the solid electrolyte test piece using a balance. For example, a heated electronic balance (AND Corp. MS-70) can be used to monitor the weight of the liquid phase evaporated over time while heating the test piece at an elevated temperature starting from 55°C. When the amount of polar compound evaporated over time reached a saturation point, this was considered to be the total amount of polar compound contained within the solid electrolyte. In the examples and comparative examples, the polar compound was ethyl methyl carbonate (EMC; boiling point: approximately 101°C), and heating at an elevated temperature to approximately 110°C was performed to measure the polar compound content.

[0210] Table 1 below shows the results of measuring the content of EMC vapor-deposited (or contained) in the electrolyte.

[0211] [Table 1]

[0212] Experimental Example 2: Measurement of ionic conductivity of electrolytes

[0213] To measure the ionic conductivity of the electrolytes prepared in the examples and comparative examples, a 1.7671 cm 2The electrolyte was formed on the lower substrate of a coin cell having a size of 1 / 2 mm, and then a coin cell for measuring ionic conductivity was manufactured using SUS (Steel Use Stainless Steel) as an inert electrode (blocking electrode).

[0214] Resistance was measured using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) at 25°C with an amplitude of 10 mV and a scan range of 1 Hz to 0.1 MHz, and the ionic conductivity of the electrolyte was calculated using the following equation 2:

[0215] [Formula 2]

[0216]

number

[0217] In the above formula 2, σ i is the ionic conductivity of the electrolyte (S / cm), R is the resistance of the electrolyte (Ω) measured by the electrochemical impedance spectrometer, L is the thickness of the electrolyte (μm), and A is the area of ​​the electrolyte (cm 2 The electrolyte sample had a thickness of L = 200 μm and an A = 1.7671 cm 2 The following items were used.

[0218] Experimental Example 3: Measurement of the activation energy of electrolytes at different temperatures

[0219] Ionic conductivity (σ) of electrolyte film at different temperatures i ) was measured in the same manner as in Experimental Example 2. Based on the measurement results, log(σ i The relationship between 1000 / T (where T is the absolute temperature at which the ionic conductivity was measured) and 1000 / T (where T is the absolute temperature at which the ionic conductivity was measured) was fitted to the Arrhenius equation shown in Equation 3 below, and Ea, which corresponds to the slope, was derived.

[0220] [Formula 3]

[0221]

number

[0222] In the above formula, σ i、0 denotes the maximum ionic conductivity of the electrolyte, and σ i denotes the ionic conductivity of the electrolyte measured at absolute temperature T, Ea denotes the activation energy of the electrolyte at absolute temperature T, and R denotes the gas constant.

[0223] Experimental example 4: Charge / discharge test for solid-state batteries

[0224] To evaluate the galvanostatic cycling characteristics of the solid-state batteries fabricated in the Examples and Comparative Examples, a charge-discharge test was conducted on the solid-state batteries in the voltage range of 3.0 V to 4.25 V using a TOSCAT charge-discharge tester (manufactured by Toyo Systems Co., Ltd.). For the solid-state batteries fabricated in the Examples, a charge-discharge test was conducted at room temperature (25°C) and a charge-discharge rate of 0.03 C. After reaching a cut-off voltage of 4.25 V, a constant voltage (CV) charge was additionally conducted at a cut-off current of 0.01 C. Additionally, for the solid-state batteries containing the solid electrolytes of the Comparative Examples, a charge-discharge test was conducted at 25°C and 60°C, respectively, at a charge-discharge rate of 0.03 C.

[0225] First, the evaluation results of the ionic conductivity of each electrolyte of the Examples and Comparative Examples measured in the above Examples are summarized in Table 2 below.

[0226] [Table 2]

[0227] Furthermore, from the measurement and evaluation results of Experimental Examples 2 and 3, the activation energy and log(σ i) are compared and shown in Figure 1. Referring to Figure 1, it was confirmed that the electrolyte of the example not only had an activation energy deviation (ΔEa) of 0.02 eV or less depending on the temperature, but also showed almost no change in activation energy and ionic conductivity depending on the absolute temperature, and excellent ionic conductivity at all temperatures.

[0228] The comparative electrolyte also showed lower activation energy values ​​across the entire temperature range compared to the comparative example. This indicates that the energy barrier required for the ion transfer mechanism based on ion hopping was lowered due to the interaction between the vapor-deposited polar compound and the polymer chain, and this characteristic was confirmed to be consistent across the entire temperature range, including low and high temperatures. In contrast, the comparative electrolyte showed a large change in activation energy and ionic conductivity with changes in absolute temperature, and in particular, showed a tendency for a rapid decrease in ionic conductivity in the low temperature range and relatively poor ionic conductivity. This suggests that the charge / discharge behavior will be affected not only at low temperatures but also at room temperature, ultimately limiting the realization of a solid-state battery that can be operated at room temperature.

[0229] Furthermore, from the evaluation results of Experimental Example 4, the results of the charge-discharge test at room temperature for the solid battery of Example 1 are shown in FIG. 2, and the results of the charge-discharge test at room temperature and at a high temperature (60°C) for the solid battery of Comparative Example 1 are shown in FIG. 3.

[0230] 2 and 3, the solid-state battery of the Example exhibits excellent charge / discharge characteristics at room temperature due to the inclusion of a solid electrolyte with high ionic conductivity of 1.3 mS / cm, whereas the solid-state battery of the Comparative Example is essentially unable to operate at room temperature due to the low ionic conductivity of the solid electrolyte, and can only be operated at high temperatures above 60°C, similar to conventional all-solid-state batteries containing PEO-based polymer solid electrolytes. In particular, in terms of discharge capacity and coulombic efficiency, the charge / discharge characteristics of the battery of the Example at room temperature were found to be superior to those of the Comparative Example at 60°C.

Claims

1. Polymers including PEO (polyethylene oxide)-based polymers containing cross-linkable functional groups; ceramic compounds; and polar compounds, at least a portion of the cross-linking functional groups form cross-links to form a three-dimensional network structure of the polymer, and the polar compound is at least one of being contained within the three-dimensional network structure and being bound to a chain of the polymer; The activation energy difference (ΔEa) according to temperature, as defined by the following formula 1, is 0.03 eV or less: [Formula 1] ΔE ａ =E ａ ＬＴ -E ａ ＨＴ In the above formula 1, E ａ ＬＴ is the activation energy of the electrolyte from -40°C to 10°C, and E ａ ＨＴ is the activation energy of the electrolyte at 10°C to 80°C, and ΔE ａ represents the activation energy difference at each temperature defined as the difference between the two activation energies, The polar compound is contained in an amount of 0.1 wt % or more and less than 10 wt % based on the total weight of the electrolyte.

2. 2. The electrolyte according to claim 1, wherein at least a portion of the polar compound is dispersed among polymer chains that form the three-dimensional network structure in a vapor-deposited gaseous state, or is adsorbed or bonded to the surface or interior of the polymer chains.

3. The electrolyte of claim 1 further comprising a multifunctional crosslinker.

4. The electrolyte according to claim 3 , wherein at least a portion of the cross-linkable functional groups form cross-links with each other via the multifunctional cross-linking agent.

5. 4. The electrolyte according to claim 3, wherein the polyfunctional crosslinking agent comprises a polyfunctional compound having a plurality of curable functional groups selected from the group consisting of a (meth)acrylic functional group, an alkoxy functional group, a peroxide functional group, a vinyl functional group, a hydroxy group, an epoxy functional group, and an allyl group.

6. the cross-linkable functional group is bonded to the PEO-based polymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (wherein an alkylene linker having 0 carbon atoms represents a single bond); 2. The electrolyte of claim 1, wherein the group is selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

7. 10. The electrolyte of claim 1 further comprising a lithium salt.

8. 8. The electrolyte according to claim 7, wherein the lithium salt is contained in an amount of 25 to 45 parts by weight based on 100 parts by weight of the PEO-based polymer.

9. The electrolyte according to claim 1, wherein the PEO-based polymer is a copolymer containing repeating units of the following chemical formulas 1 to 3: [Chemical formula 1] 【Chemistry 1】 [Chemical formula 2] 【Chemistry 2】 [Chemical formula 3] 【Transformation 3】 In the above chemical formulas 1 to 3, R １ is -CH ２ -O-(CH ２ -CH ２ -O) ｋ -R ３ where k is 0 to 20, and R ３ represents an alkyl group having 1 to 5 carbon atoms, R ２ represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), l, m, and n are the number of repeating units, l and n are each independently an integer of 1 to 100,000, and m is an integer of 0 to 100,000.

10. 10. The electrolyte of claim 1, wherein the PEO-based polymer has a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol.

11. 2. The electrolyte according to claim 1, wherein the polar compound is contained in an amount of 1.2% by weight or more and less than 6% by weight based on the total weight of the electrolyte.

12. The electrolyte according to claim 1 , wherein the polar compound comprises at least one selected from the group consisting of carbonate-based compounds and sulfonyl-based compounds.

13. 2. The electrolyte of claim 1, wherein the polar compound comprises at least one selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane.

14. 10. The electrolyte of claim 1, wherein the ceramic compound comprises an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate.

15. 2. The electrolyte of claim 1, wherein the ceramic compound comprises one or more oxide-based solid electrolytes selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO) compounds, lithium-silicon titanium phosphate (LSTP) compounds, lithium-lanthanum-titanium oxide (LLTO) compounds, lithium-aluminum-titanium phosphate (LATP) compounds, lithium-aluminum-germanium phosphate (LAGP) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds.

16. 2. The electrolyte according to claim 1, wherein the ceramic compound is contained in an amount of 10 to 100 parts by weight based on 100 parts by weight of the PEO-based polymer.

17. 2. The electrolyte of claim 1, wherein the ceramic compound is contained in particles having a diameter of 100 nm to 1000 nm.

18. A solid state battery comprising an electrolyte layer comprising the electrolyte according to any one of claims 1 to 17.

19. A method for producing an electrolyte according to any one of claims 1 to 17, comprising the steps of: A PEO-based polymer containing a cross-linkable functional group is mixed with a ceramic compound, A crosslinking reaction is carried out in the presence of a crosslinking agent in a certain ratio with respect to the PEO-based polymer contained in the mixture; vapor-depositing a polar solvent onto the crosslinked resultant; method.

20. A method for producing a solid-state battery comprising an electrolyte layer comprising the electrolyte according to any one of claims 1 to 17, A PEO-based polymer containing a cross-linkable functional group is mixed with a ceramic compound, A crosslinking reaction is carried out in the presence of a crosslinking agent in a certain ratio with respect to the PEO-based polymer contained in the mixture; By vapor-depositing a polar solvent onto the crosslinked resultant, Forming an electrolyte layer, The positive electrode, the electrolyte layer, and the negative electrode are laminated in a sandwich type. method.

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