Electrolyte and all-solid-state battery comprising same

Abstract

The present invention relates to an electrolyte and an all-solid-state battery comprising same. The electrolyte comprises: a polymer containing a polyethylene oxide (PEO)-based polymer including a cross-linkable functional group; a ceramic compound; and a polar compound, wherein: at least a portion of the cross-linkable functional group forms a cross-linkage via a cross-linking agent to allow the polymer to form a three-dimensional network structure; the polar compound is included in the three-dimensional network structure or is bonded on the polymer chain; and the content of the polar compound and the weight percentage of the cross-linking agent satisfy predetermined ranges.

Description

Electrolyte and all-solid-state battery containing the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0123075, filed September 15, 2023, Korean Patent Application No. 10-2024-0048814, filed April 11, 2024, and Korean Patent Application No. 10-2024-0123907, filed September 11, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to an electrolyte and an all-solid-state battery including the same.

[0004] Lithium-ion batteries using liquid electrolytes have a structure where the anode and cathode are separated by a separator. Damage to the separator due to deformation or external impact can cause a short circuit, potentially leading to risks such as overheating or explosion. Therefore, the development of a solid electrolyte that can ensure safety in lithium-ion secondary batteries is a critical task.

[0005] Lithium secondary batteries using solid electrolytes offer enhanced safety, improved reliability by preventing electrolyte leakage, and the ease of manufacturing thin batteries. Furthermore, the use of lithium metal as the anode enhances energy density. Consequently, solid electrolytes are expected to find applications in small-sized secondary batteries as well as high-capacity secondary batteries for electric vehicles, drawing attention as next-generation batteries.

[0006] Among solid electrolytes, polymer solid electrolytes can use polymer materials with ion-conducting properties, and can be used in the form of composite solid electrolytes that mix inorganic materials with these polymer 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 advantage of superior stability against ignition and combustion compared to conventional liquid electrolytes, and higher ionic conductivity compared to polymer solid electrolytes.

[0008] However, existing composite solid electrolytes have the difficulty of meeting basic prerequisites 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 a highly crystalline polymer such as polyethylene oxide (PEO) is used as the matrix, there was a problem that it was difficult to manufacture an electrolyte with improved ionic conductivity. In other words, because the high crystallinity of the PEO polymer inhibits the chain mobility of the polymer, and the movement of lithium ions within the polymer solid electrolyte is restricted, there was a limit to improving the ionic conductivity of the polymer solid electrolyte.

[0009] The present invention provides an electrolyte in the form of a composite solid electrolyte exhibiting improved ionic conductivity.

[0010] In addition, the present invention provides an all-solid-state battery including the electrolyte and exhibiting improved ionic conductivity, etc.

[0011] According to one embodiment of the invention, there is provided an electrolyte comprising a polymer including a PEO (polyethylene oxide) polymer having a cross-linking functional group; a ceramic compound; and a polar compound.

[0012] At least a portion of the above cross-linking functional groups form cross-links via a cross-linking agent, so that the polymer forms a three-dimensional network structure,

[0013] The polar compound is included in the three-dimensional network structure or is bonded on the polymer chain, and is included in an amount of 0.1 wt% or more and less than 10 wt% based on the total weight of the electrolyte,

[0014] An electrolyte is provided in which the crosslinking agent is included in a weight ratio of 0.07 to 0.19 with respect to the weight of the PEO polymer including the crosslinking functional group.

[0015] In such an electrolyte, at least a portion of the polar compound may be dispersed between 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.

[0016] In addition, in the electrolyte, the crosslinking agent may include a multifunctional compound having multiple 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 hydroxyl group, an epoxy functional group, and an allyl group.

[0017] In addition, the PEO polymer may include one or more, or two or more, cross-linking functional groups, and the cross-linking functional groups may be bonded to a polymer chain via an alkylene linker or an alkylene oxide linker having 0 to 10 carbon atoms (provided that the alkylene linker having 0 carbon atoms represents a single bond) in the PEO polymer, and may be 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.

[0018] In addition, the electrolyte may further include the lithium salt, and at least some of the lithium salt may be included in the form of dissociated cations and anions. The cations and / or anions may exist in a state bound to the polymer phase and may move during charging / discharging of the battery. The lithium salt may be included in an amount of 25 to 45 parts by weight based on 100 parts by weight of the PEO polymer including the cross-linking functional group.

[0019] In a specific embodiment, the PEO polymer of the electrolyte may be a copolymer comprising repeating units of the following chemical formulae 1 to 3:

[0020] [Chemical Formula 1]

[0021]

[0022] [Chemical Formula 2]

[0023]

[0024] [Chemical Formula 3]

[0025]

[0026] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k-R3 represents, k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms, R2 represents a substituent in which at least one cross-linking 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 is bonded to a polymer chain via an alkylene linker or an alkylene oxide linker having 0 to 10 carbon atoms (provided that the alkylene linker having 0 carbon atoms represents a single bond), l, m, and n represent the number of repetitions of the repeating unit, l and n are each independently an integer from 1 to 100000, and m is an integer from 0 to 100000.

[0027] These PEO polymers can have a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol.

[0028] In addition, 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 and 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.

[0029] In addition, the ceramic compound may include an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate, and more specifically, may include at least one oxide-based solid electrolyte selected from the group consisting of a lithium-lanthanum-zirconium oxide-based (LLZO) compound, a lithium-silicon titanium phosphate-based (LSTP) compound, a lithium-lanthanum-titanium oxide-based (LLTO) compound, a lithium-aluminum-titanium phosphate-based (LATP) compound, a lithium-aluminum-germanium phosphate-based (LAGP) compound, and a lithium-lanthanum-zirconium-titanium oxide-based (LLZTO) compound.

[0030] In addition, the ceramic compound may be included in the form of particles having a diameter of 100 nm to 1000 nm, and may be included in an amount of 10 to 100 parts by weight relative to 100 parts by weight of the polymer mixture.

[0031] Meanwhile, according to another embodiment of the invention, an all-solid-state battery is provided including an electrolyte layer including the electrolyte of the above-described embodiment.

[0032] An electrolyte according to one embodiment of the invention can improve the ionic conductivity of an electrolyte by improving the mobility of polymer chains and uniformly distributing ceramic particles within the electrolyte while maintaining the original structural characteristics of the polymer without deformation or destruction of the polymer chains.

[0033] Additionally, the electrolyte can exhibit improved ionic conductivity and mechanical properties by including a trace amount of polar compound, for example, in a vapor-deposited state.

[0034] 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, thereby improving the mobility of the polymer chains, thereby improving the ionic conductivity without deteriorating the mechanical properties.

[0035] Furthermore, the electrolyte can maximize the effect of improving ion conductivity by vapor deposition by optimizing the crosslinking bond formation ratio by the crosslinking agent, and can also exhibit improved mechanical properties.

[0036] Figure 1 is a graph showing the change in ionic conductivity according to the weight ratio of the crosslinking agent for the electrolytes of examples and comparative examples.

[0037] Hereinafter, specific implementation examples of the invention will be described in more detail to help understand the invention.

[0038] The terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0039] The term "bond" as used herein may mean a form in which a polar compound is "bonded" to a polymer chain, for example, a chain of a PEO polymer having a cross-linking functional group. This "bond" broadly means a form in which, for example, a gaseous polar compound is maintained in a fixed state on a polymer chain by vapor deposition of a polar solvent. The "bond" is not limited to a specific physical, chemical bond, etc., and is used to mean a state in which it is fixed by various bonds including these physical, chemical bonds, etc., or a state in which it is simply attached and fixed, such as by adsorption, or a state in which it is fixed by being included in a three-dimensional network structure formed by cross-linking of the polymer and positioned adjacent to the polymer chain or cross-linking structure.

[0040] 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, wherein the frame may include a polymer chain including a cross-link formed by the cross-linkable functional group, for example, a cross-link between the cross-linkable functional groups and / or a cross-link between the cross-linkable functional group and a cross-linking agent. The three-dimensional network structure may also be referred to as a cross-linked structure.

[0041] In this specification, the existence or inclusion of a polar compound (polar solvent) in the electrolyte in a “gaseous state” defines a state that is distinct from a case where the polar solvent or an electrolyte or polar solution containing the polar compound is injected in a liquid state. That is, it indicates that the polar compound is deposited in the electrolyte in a vaporous state and exists in a state that is distinct from a case where the polar solvent, etc. is injected in a liquid state immediately after the preparation of the electrolyte or during the charging and discharging process of an all-solid-state battery containing the electrolyte. However, depending on the storage or operating conditions of the electrolyte and / or the battery, the vapor-deposited polar compound may be locally or temporarily liquefied. Even in this case, the vapor-deposited polar compound exhibits higher mobility than the liquid-injected polar solvent, etc., and thus exhibits a different state, and therefore, it can also be regarded as existing or included in the “gaseous state.”

[0042]

[0043] Meanwhile, to improve the ionic conductivity of solid electrolytes, electrolytes were previously manufactured by dispersing ceramic compounds, such as oxides, within a polymer matrix. However, these electrolytes have been problematic in that ionic conductivity is reduced when the oxide ceramic particles within the polymer matrix are unevenly distributed or when a highly crystalline polymer, such as polyethylene oxide, is used.

[0044] Accordingly, in order to improve the ionic conductivity of the solid electrolyte and enhance the dispersibility of the ceramic compound, the solid electrolyte was immersed or supported in an electrolyte or a liquid solvent, or the electrolyte or polar solvent was directly injected into the solid electrolyte in a liquid state. When a significant amount of electrolyte or polar solvent is directly added to the solid electrolyte in this way, the ionic conductivity of the solid electrolyte is improved to some extent. However, in this case, the excellent safety and stability according to the application of the solid electrolyte may be impaired. In addition, the improvement in ionic conductivity due to the addition of the electrolyte or polar solvent was not sufficient, so the injection of a significant amount of polar solvent, etc. was required.

[0045] In addition, when a liquid electrolyte or polar solvent is directly added or injected into a solid electrolyte in a liquid state, there is a problem that the structure of the solid electrolyte collapses due to unexpected side reactions between the polymer and the liquid phase, such as damage to the polymer chains or breakage of bonds within the polymer, or a decrease in ionic conductivity due to this. Moreover, there is a disadvantage that this ionic conductivity decreases even more at low temperatures, where ion mobility within the liquid electrolyte is reduced.

[0046] In addition, when a polar solvent or liquid electrolyte is directly injected into a solid electrolyte, liquid molecules rapidly diffuse within the solid electrolyte, rapidly causing relaxation of polymer chains, which may promote gelation on the surface and result in a decrease in mechanical properties. In addition, problems such as leakage of the liquid electrolyte or polar solvent may occur, which may lower the safety of the battery.

[0047] Accordingly, the inventors of the present invention applied a method of vapor depositing a polar compound derived from a polar solvent onto an electrolyte comprising a polymer cross-linked with a PEO (polyethylene oxide) polymer modified with a cross-linking functional group and a ceramic compound. An electrolyte of one embodiment manufactured in this manner comprises a polymer including a PEO polymer including a cross-linking functional group; a ceramic compound and a polar compound, wherein at least some of the cross-linking functional groups form cross-links with each other so that the polymer forms a three-dimensional network structure, and the polar compound may be included in the three-dimensional network structure or may exhibit a structure bonded on the polymer chain.

[0048] It has been confirmed that these electrolytes exhibit enhanced ionic conductivity while containing polar compounds derived from trace amounts of polar solvents. In these electrolytes, the polar compounds may exhibit a state different from that of the polar solvent injected in a large amount in a liquid phase due to the vapor deposition and trace amounts thereof. For example, the polar compounds may exist in a gaseous state at least partially within the electrolyte, and may be locally or temporarily converted into a liquid or gas-liquid coexistence state during battery operation. In addition, 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 polymer chains between the three-dimensional networks.

[0049] It is predicted that the different states of these polar compounds will affect the physical properties of the PEO polymer, such as crystallinity, thereby increasing the chain mobility of the polymer chains and thereby improving the conductivity of lithium ions contained in the electrolyte. Furthermore, the electrolyte can exhibit even better ionic conductivity due to the ceramic compound uniformly dispersed within the three-dimensional network structure.

[0050] The polar compound may be included 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%. When the content of the polar compound is less than 0.1 wt%, it is difficult to induce a change in the chain conformation within the polymer, and thus it is difficult to sufficiently improve the ionic conductivity of the electrolyte despite vapor deposition of the polar compound. Conversely, when the content of the polar compound is 10 wt% or more, it exhibits the same state as a liquid-injected polar solvent within the electrolyte, and it becomes difficult to obtain the effect of vapor deposition. Accordingly, the content of polar solvent or electrolyte, which is practically always in a liquid state, is large in the electrolyte, resulting in the characteristics of a semi-solid battery, and the mechanical strength of the electrolyte may be reduced due to gelation of the polymer, and the ionic conductivity of the electrolyte may also be insufficient.

[0051] The content of the polar compound included in the electrolyte of the above embodiment can be calculated by measuring the content of the polar compound that evaporates while heating the electrolyte. Specifically, considering the boiling point and temperature-dependent vapor pressure of the polar compound, the content can be calculated by heating at a temperature at which the polar compound begins to evaporate, for example, at a temperature of 40°C or higher or 50°C or higher, to a temperature of the boiling point or the boiling point + 10°C, collecting the polar compound that evaporates within the temperature range in a liquid phase, and measuring the weight of the liquid phase. The calculation can be stopped when the measured amount reaches a saturation state (for example, when the measured amount no longer increases) as the heating time under the above temperature increase elapses, and this can be regarded as the total amount of the polar compound included in the electrolyte.

[0052] In addition, the content of the polar compound included in the electrolyte can be controlled through the amount of polar compound used and / or the progress conditions such as the progress time or temperature of the vapor deposition in the vapor deposition step described later.

[0053] Meanwhile, the electrolyte can optimize the degree of formation of the three-dimensional network structure by optimizing the proportion of cross-linking agent used to form the cross-linking bond. As a result, the ionic conductivity enhancement effect due to vapor deposition of the polar compound can be maximized, and improved mechanical properties can also be exhibited.

[0054] Therefore, the electrolyte of one embodiment exhibits improved ionic conductivity without substantially including a liquid polar solvent or electrolyte, thereby contributing to the development of an all-solid-state battery having excellent physical properties.

[0055] In the electrolyte of the above-described embodiment, the crosslinking agent may be included in a weight ratio of 0.07 to 0.19, or 0.07 to 0.18, or 0.08 to 0.15, or 0.08 to 0.13 with respect to the weight of the PEO polymer.

[0056] If the weight ratio of the cross-linking agent is excessively low, the three-dimensional network structure formed by cross-linking is not properly formed, which not only deteriorates the mechanical properties of the electrolyte, but also prevents proper vapor deposition of polar compounds and significantly deteriorates ionic conductivity. Conversely, if the weight ratio of the cross-linking agent is excessively high, it has been confirmed that the ionic conductivity of the electrolyte is reduced.

[0057] In a specific example, the polar compound may be dispersed between polymer chains forming the three-dimensional network structure, or may be adsorbed or bound to the surface or interior of the polymer chain.

[0058] These electrolytes include polar compounds that are incorporated or bound in a three-dimensional network structure in small amounts by vapor deposition, as described below. These polar compounds have a state different from that of a polar solvent that is injected in large quantities into the electrolyte in a liquid state. The state of these polar compounds can be confirmed, for example, by separating an electrolyte layer including the polar compound from an all-solid-state battery or the like at a temperature lower than the boiling point of the polar compound, and then observing it with the naked eye or an electron microscope. Under such observation, if no liquid component is observed on the surface of the electrolyte layer, it can be considered to have a state similar to that of an electrolyte of one embodiment in which the polar compound is vapor deposited.

[0059] In contrast, when a liquid polar solvent or electrolyte is injected into the electrolyte, a liquid component or a component exhibiting wettability can be observed on the surface of the electrolyte layer. In addition, as confirmed through the examples described below, the electrolyte of one embodiment in which the polar compound is vapor-deposited exhibits improved ionic conductivity despite a low content of the polar compound, compared to the case in which a liquid polar solvent or electrolyte is injected. Through a comparison of ionic conductivities, etc., an electrolyte in which the polar compound is vapor-deposited and included in a gaseous state, etc. can be confirmed.

[0060] Meanwhile, in the electrolyte of the above embodiment, the cross-linkable functional group may be directly bonded to the main chain of the PEO polymer, or may be bonded via an alkylene or alkylene oxide linker. Accordingly, the cross-linkable functional group may be bonded via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (provided that the alkylene linker having 0 carbon atoms represents a single bond), and may be at least one 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.

[0061] In one embodiment of the invention, the cross-linking functional groups may be 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. Furthermore, when multiple types of cross-linking functional groups are included, the mobility and ionic conductivity of the polymer chain may be more easily controlled.

[0062] The above cross-linking functional group refers to a functional group that can form a cross-linking bond with each other through a cross-linking agent, and can be bonded to a polymer chain in the form of a side chain.

[0063] In a more specific embodiment, the PEO polymer including the cross-linking functional group may be a copolymer including repeating units of the following chemical formulae 1 to 3:

[0064] [Chemical Formula 1]

[0065]

[0066] [Chemical Formula 2]

[0067]

[0068] [Chemical Formula 3]

[0069]

[0070] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3 represents, k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms,

[0071] R2 represents a substituent in which at least one cross-linking 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 is bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (provided that the alkylene linker having 0 carbon atoms represents a single bond).

[0072] l, m and n are the repetition numbers of the repeating unit, l and n are each independently an integer from 1 to 100000, or from 50 to 80000, or from 100 to 50000, and m is an integer from 0 to 100000, or from 50 to 80000, or from 100 to 50000.

[0073] For example, the cross-linking functional group of R2 can form a matrix polymer having a three-dimensional network structure formed by the cross-linking. By forming a three-dimensional network structure by the cross-linking, the mechanical properties of the electrolyte can be improved, and an electrolyte of one embodiment having improved ionic conductivity can be provided by including or combining the polar compound within the three-dimensional network structure.

[0074] In addition, it is obvious that the PEO polymer may include two or more types of repeating units of chemical formula 3 in which R2 is a different cross-linking functional group, and may also include one or more types of repeating units of chemical formula 2.

[0075] When the above l, m and n are each too small, it is difficult to form a polymer due to the small molecular weight, and when the above l, m and n are each too large, the solubility may decrease when preparing a polymer solution due to an increase in viscosity, and molding for preparing an electrolyte may become difficult. In particular, when the number of repeating units containing a cross-linking functional group among l, m and n is too large, the degree of cross-linking may increase excessively, which may lower the mobility of the polymer chain and reduce ionic conductivity.

[0076] In this specification, “hydroxy group” refers to an -OH group.

[0077] In this specification, “carboxyl group” refers to a -COOH group.

[0078] In this specification, “isocyanate group” refers to a -N=C=O group.

[0079] In this specification, “nitro group” refers to a -NO2 group.

[0080] In this specification, “cyano group” refers to a -CN group.

[0081] In this specification, “amide group” refers to -C(=O)NR'R”, wherein R' and R" can each independently be hydrogen or a C1 to C5 alkyl group, or R' and R" together with the N atom to which they are attached can form a heterocycle having C4 to C8 atoms within the ring structure.

[0082] In the present specification, the “amine group” may be selected from the group consisting of a monoalkylamine group; a monoarylamine group; a monoheteroarylamine group; a dialkylamine group; a diarylamine group; a diheteroarylamine group; an alkylarylamine group; an alkylheteroarylamine group; and an arylheteroarylamine group, and the number of carbon atoms is not particularly limited, but is preferably 1 to 30. Specific examples of the above amine group include, but are not limited to, a methylamine group, a dimethylamine group, an ethylamine group, a diethylamine group, a phenylamine group, a naphthylamine group, a biphenylamine group, a dibiphenylamine group, an anthracenyl amine group, a 9-methyl-anthracenylamine group, a diphenylamine group, a phenylnaphthylamine group, a ditolylamine group, a phenyltolylamine group, a triphenylamine group, a biphenylnaphthylamine group, a phenylbiphenyl amine group, a biphenylfluorenylamine group, a phenyltriphenylenyl amine group, and a biphenyltriphenylenyl amine group. In addition, “amino group” refers to -NH2.

[0083] In this specification, “allyl group” refers to a -CH2-CH=CH2 group.

[0084] The weight average molecular weight (Mw) of the polymer comprising the above chemical formulas 1 to 3 may be 100,000 g / mol to 4,000,000 g / mol, specifically, may be 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, and 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 electrolyte to be manufactured may not be satisfied. If the weight average molecular weight (Mw) of the polymer is too large, the solubility may decrease during the manufacture of a polymer solution due to an increase in viscosity, and molding for the manufacture of the electrolyte may become difficult. In addition, the ionic conductivity of the electrolyte may decrease due to an increase in crystallinity and a decrease in chain mobility within the electrolyte.

[0085] In particular, if the number of repeating units of the chemical formula 3 containing cross-linking functional groups among l, m and n is excessively large, the degree of cross-linking may increase excessively, which may lower the mobility of the polymer chain and reduce the ionic conductivity of the electrolyte.

[0086] Additionally, the polymer may be a copolymer comprising each of the above repeating units, for example, a random copolymer or a block copolymer.

[0087] Meanwhile, in a specific embodiment of the invention, the polar compound may be included or bound to the surface or interior of the polymer chain, for example, in a substantially gaseous state (including a local, temporary liquid state) by vapor deposition. Specifically, the polar compound may be diffused or dispersed between polymer chains that form a three-dimensional network structure by crosslinking of the crosslinkable PEO polymer, or may be adsorbed or bound to the surface or interior of the polymer chain.

[0088] The above polar compound is a gas molecule of a polar solvent used in a vapor deposition process, and when the gas molecule of the polar solvent is adsorbed to the polymer during vapor deposition, it diffuses into the polymer chain, and is bound to the polymer chain, or is included in a form dispersed or diffused in the internal space between the polymer chains. By including the polar compound in a form bound to the polymer chain or dispersed in the internal space between the polymer chains, the ionic conductivity of the final manufactured electrolyte can be improved despite its low content.

[0089] Specifically, the polar compound bound to the polymer chain or included between the polymer chains can act as a plasticizer, thereby plasticizing the polymer. The plasticized polymer can have an increased amorphous region within it, thereby improving the mobility of the polymer chains. As the mobility of the polymer chains is improved, the ion hopping effect within the polymer is enhanced, thereby improving the ionic conductivity of the electrolyte.

[0090] In addition, the polar compound can act as an intermediate for smooth ion transfer through ion hopping. Since the affinity between lithium ions and the polar compound is stronger than the affinity between lithium ions and the ether oxygen of the PEO polymer, the transfer of lithium ions can be faster and easier inside the polymer to which the polar compound is adsorbed. That is, as the polar compound is introduced into the polymer, the cation solvation effect of lithium ions is increased, so that ion mobility is improved, and thus the ion conductivity of the electrolyte can be improved.

[0091] Additionally, the polar compound may include at least one selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0092] 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, or may include a combination thereof.

[0093] As described above, the content of the polar compound may include 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 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%.

[0094] In one embodiment of the invention, the electrolyte may further comprise a cross-linking agent in the above-described proportion, thereby allowing cross-linking between the cross-linking agent and the cross-linking functional group. For example, at least a portion of the cross-linking functional groups may form cross-links with each other via the cross-linking agent, thereby forming the three-dimensional network structure described above.

[0095] At this time, a crosslinking bond may be formed between the crosslinking agent and the crosslinking functional group, and the crosslinking bond may be a bond formed by a hydrogen bond, a bond by Lewis acid-base interaction, an ionic bond, a coordination bond, or radical polymerization.

[0096] The cross-linking agent is not particularly limited as long as it is a polyfunctional cross-linking agent that includes a plurality of curable functional groups capable of forming cross-linking bonds with the cross-linking functional group. For example, the cross-linking agent may be selected from at least one polyfunctional compound that has 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 hydroxyl group, an epoxy functional group, and an allyl group.

[0097] In a more specific example, the crosslinking agent is trimethylolpropane trimethacrylate, poly(ethylene glycol) diacrylate, poly(ethylene 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 3-(acryloyloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acryloylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3isocyanatopropyltriethoxysilane, 3-methylacryloxypropyl trimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene, ethylene glycol maleic rosinate acrylate glycol maleic rosinate acrylate),Glycidylmethacrylate, hydroxyquinoline, iphenyldiethoxysilane, maleic rosin glycol acrylate, methylene bisacrylamide, N,N'-1,4-phenylenediacrylamine, N,O-bisacryloyl-phenylalaninol, N,O-bismethacryloyl ethanolamine, pentaerythritol triacrylate, phenyltrimethoxy silane, At least one polyfunctional crosslinking agent selected from the group consisting of tetramethoxysilane, tetramethylene, tetraethoxysilane, and triallyl isocyanurate, for example, a compound having two or more functional groups.

[0098] In addition, the cross-linking agent may be included in a weight ratio of 0.07 to 0.19, or 0.07 to 0.18, or 0.08 to 0.15, or 0.08 to 0.13 relative to the weight of the PEO polymer including the cross-linking functional group. If the weight ratio of the cross-linking agent becomes excessively small, the formation of a three-dimensional network structure may not occur properly, making it difficult to apply vapor deposition, and as a result, the ionic conductivity of the electrolyte may be significantly reduced. Conversely, if the weight ratio of the cross-linking agent becomes excessively large, cross-linking and a three-dimensional network structure may be excessively formed, which may rather reduce the mobility of the polymer chain, thereby lowering the ionic conductivity.

[0099] In one embodiment of the invention, the electrolyte may further comprise a lithium salt. The lithium salt may be incorporated in the internal space between the polymer chains in a dissociated ionic state, thereby enhancing the ionic conductivity of the electrolyte. At least a portion of the dissociated cations and / or anions in the lithium salt may remain bound to the polymer chains, thereby exhibiting mobility during charging / discharging of the battery.

[0100] The lithium salt is (CF3SO2)2NLi(Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi(Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylic acid, and lithium tetraphenylborate.

[0101] In addition, the lithium salt may be included in an amount of 25 to 45 parts by weight based on 100 parts by weight of the PEO-based polymer including the cross-linking functional group, and specifically, may be included in an amount of 25 parts by weight or more, 30 parts by weight or more, or 35 parts by weight or more, or may be included in an amount of 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 be reduced, and if it exceeds 45 parts by weight, the mechanical strength may be reduced.

[0102] The electrolyte described above may include a ceramic compound. The ceramic compound has a lithium ion transport capability to improve the conductivity of lithium ions, preferably contains lithium atoms but has the function of transporting lithium ions without storing lithium, thereby improving the ion conductivity of the electrolyte.

[0103] Additionally, the ceramic compound may be uniformly dispersed between cross-linked polymer chains, for example, within the three-dimensional network structure. The ceramic compound may be added together during the cross-linking process, and may be uniformly dispersed without agglomeration between the polymer chains formed by the cross-linking. Such a ceramic compound may be advantageous in improving the mechanical strength and ionic conductivity of the electrolyte due to its uniform dispersion form.

[0104] In addition, the ceramic compound may be in the form of particles. Due to the morphological characteristics of particles, they may be included in a more uniformly dispersed state within the electrolyte. The particles of the ceramic compound may be spherical and may have a diameter of 100 nm to 1000 nm. If the diameter is less than 100 nm, the non-crystallization effect due to a decrease in the crystallinity of the polymer may be minimal, and if it exceeds 1000 nm, the dispersibility may be reduced due to an increase in aggregation between particles, making it difficult to uniformly disperse them.

[0105] The ceramic compound may be an oxide-based or phosphate-based compound, and may be, for example, an oxide-based solid electrolyte in the form of a lithium metal oxide or a lithium metal phosphate. More specifically, the ceramic compound may be a garnet-type lithium-lanthanum-zirconium oxide (LLZO, Li7La3Zr2O 12 ) compound, perovskite type lithium-lanthanum-titanium oxide system (LLTO, Li3xLa 2 / 3-xTiO3) compound, NASICON type lithium-aluminum-titanium phosphate (LATP, Li) of phosphate type 1+x Al x Ti 2-x (PO4)3) compound, lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5 (PO4)3) compounds, lithium-silicon-titanium phosphate (LSTP, LiSiO2TiO2(PO4)3) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds, and more preferably, at least one oxide-based solid electrolyte selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO), lithium-silicon-titanium phosphate (LSTP), lithium-lanthanum-titanium oxide (LLTO), lithium-aluminum-titanium phosphate (LATP), lithium-aluminum-germanium phosphate (LAGP), and lithium-lanthanum-zirconium-titanium oxide (LLZTO) can be used.

[0106] The above oxide-based or phosphate-based oxide-based solid electrolytes generally have a maximum temperature of 10 -4 ~10 -3 It has an ionic conductivity value of S / cm, is stable in the high voltage range, is stable in air, and has the advantages of being easy to synthesize and handle.

[0107] Therefore, the above-described electrolyte can supplement the shortcomings of the polymer-based solid electrolyte by further including the electrolyte by mixing the above-described ceramic compound.

[0108] In addition, the ceramic compound exhibits high high-temperature stability as it does not easily combust or ignite even under high-temperature conditions of 400°C or higher. Therefore, when the electrolyte includes the ceramic compound, the mechanical strength of the electrolyte, as well as high-temperature stability and ionic conductivity, can be improved.

[0109] The above ceramic compound may be included in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, based on 100 parts by weight of the PEO polymer including the cross-linking functional group.

[0110] If the above ceramic compound is included in an excessively small amount, the effect of lowering the polymer crystallinity and making it amorphous by the ceramic compound is reduced, so the effect of increasing the ionic conductivity of the electrolyte is not significant, and the mechanical properties may not reach the expected level due to the formation of a composite.

[0111] If the ceramic compound is included in an excessively large amount, the ceramic compound is not uniformly dispersed within the polymer, causing the ceramic compound particles to clump together and aggregate, resulting in the production of an electrolyte with reduced ionic conductivity.

[0112] Meanwhile, the electrolyte described above can exhibit excellent ionic conductivity. For example, the electrolyte can exhibit excellent ionic conductivity of, for example, 0.95 mS / cm or more, 1.0 mS / cm or more, or 1.0 mS / cm to 3.0 mS / cm, as measured at room temperature of about 25°C.

[0113] This ionic conductivity can be calculated from the resistance (Ω) of the electrolyte measured by an electrochemical impedance spectrometer at a constant temperature, according to the following equation 1:

[0114] [Formula 1]

[0115]

[0116] In the above equation 1, 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 (㎛), and A is the area of ​​the electrolyte (cm 2 ) means.

[0117]

[0118] Method for manufacturing electrolyte

[0119] The method for manufacturing the above-described electrolyte may include a step of mixing a PEO-based polymer containing a cross-linking functional group and a ceramic compound, and then performing a cross-linking reaction in the presence of a cross-linking agent at a certain ratio for the PEO-based polymer included in the mixture; and a step of vapor-depositing a polar solvent on the cross-linked resultant.

[0120] The description of the PEO polymer containing the above cross-linking functional group is as described above.

[0121] Below, each step is explained in more detail.

[0122] First, a PEO (polyethylene oxide) polymer containing a cross-linking functional group and a ceramic compound are mixed, and then a cross-linking reaction is performed in the presence of a cross-linking agent at a certain ratio for the PEO polymer contained in the mixture, thereby manufacturing a polymer forming the three-dimensional network structure described above.

[0123] This crosslinking reaction can proceed in the presence of a crosslinking agent and an initiator in a certain ratio as described above.

[0124] Additionally, for electrolyte formation, a lithium salt may be added together in the mixing step and / or cross-linking reaction step.

[0125] In addition, the ceramic compound may be the same as that used in the electrolyte described above, and the content may also be the same.

[0126] The above cross-linking reaction can be formed in the process of forming a coating film by applying a solution containing the PEO polymer and a ceramic compound, etc., onto a substrate and then drying the solution.

[0127] Specifically, the mixed solution can be prepared by mixing the PEO polymer and the ceramic compound in a solvent, and additionally, can be prepared by mixing a crosslinking agent, an initiator, and / or a lithium salt together. Also, a mixed solution or suspension can be prepared by first preparing a solution containing the PEO polymer and the crosslinking agent, an initiator, and / or a lithium salt, and then adding a ceramic compound.

[0128] The solvent is not particularly limited as long as it can mix the PEO polymer, crosslinking agent, 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 dimethylformamide (DMF, N,N-Dimethyl formamide). These solvents serve as a reaction medium for forming crosslinks, and are distinguished from polar solvents included in liquid electrolytes, etc., and are completely removed by drying, etc. after crosslinking.

[0129] The concentration of the above-mentioned mixed solution can be appropriately adjusted to ensure that the molding process for manufacturing the electrolyte can proceed smoothly. 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 be the concentration of a PEO-based polymer. For example, the concentration of the polymer solution may be 5 wt% to 20 wt%, and specifically, may be 5 wt% or more, 7 wt% or more, or 9 wt% or more, and 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 dilute, which may lower the mechanical strength of the electrolyte or cause it to flow when applied to a substrate. If it exceeds 20 wt%, it may be difficult to dissolve the lithium salt in the polymer solution at a desired concentration, and the viscosity may be high, which may reduce the solubility or make it difficult to apply it in a uniform thin film form.

[0130] The above substrate is not particularly limited as long as it can serve as a support for the coating film. For example, the above 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-vinylacetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film.

[0131] In addition, the coating method is not particularly limited as long as it is a method that can form a coating film by coating the polymer solution on the substrate. For example, the coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting.

[0132] The coating film formed on the substrate by the above coating method can be formed into a polymer film from which the residual solvent is completely removed through a drying process. The drying can be divided into a first drying process and a second drying process to prevent shrinkage of the polymer due to rapid evaporation of the solvent. The first drying process can remove part of the solvent through room temperature drying, and the second drying process can completely remove the solvent through vacuum high-temperature drying. The high-temperature drying can be performed at a temperature of 80°C to 130°C. If the high-temperature drying temperature is lower than 80°C, the residual solvent cannot be completely removed, and if it exceeds 130°C, the polymer may shrink, making it difficult to form a uniform electrolyte film.

[0133] In addition, the cross-linking agent may form a bond with the cross-linking functional group. The type of the cross-linking agent, the content (weight ratio) of the cross-linking agent, and the type of bond with the cross-linking functional group are as described above.

[0134] Additionally, the initiator can induce a radical polymerization reaction between the cross-linkable functional groups, thereby forming a cross-link between the cross-linkable functional groups. The functional group that enables the radical polymerization reaction may be a functional group that includes vinyl at the terminal end, for example, an allyl group.

[0135] The initiator is not particularly limited as long as it is an initiator capable of inducing a radical polymerization reaction between the cross-linking functional groups. For example, the initiator may include at least one selected from the group consisting of benzoyl peroxide, azobisisobutyronitrile, lauroyl peroxide, cumene hydroperoxide, diisopropylphenyl-hydroperoxide, tert-butyl hydroperoxide, p-methylhydroperoxide, and 2,2'-azobis(2-methylpropionitrile).

[0136] The above initiator can be used in an amount of 0.5 to 2 parts by weight based on 100 parts by weight of the PEO polymer including the cross-linking functional group, and when used in the above range, it can induce a radical polymerization reaction between the cross-linking functional groups, thereby enabling efficient formation of cross-linking.

[0137] In addition, the content and type of the lithium salt are as described above.

[0138] In the above vapor deposition step, the crosslinked resultant can be vapor deposited by exposing it to a vaporized polar compound (polar solvent).

[0139] Specifically, the vapor deposition can be performed by heating the polar solvent at a temperature higher than room temperature, bringing the vapor of a polar compound obtained by heating the polar solvent into contact with the cross-linked product and allowing it to penetrate into the interior. Through such vapor deposition, for example, a polar compound in a gaseous state is uniformly diffused on the surface and / or interior of the polymer, so that the polar compound gas molecules can be bound to the polymer chain or included in a form uniformly dispersed or diffused in the internal space of the polymer chain.

[0140] In the above vapor deposition, when a polar solvent is kept at room temperature, a small amount of a polar solvent with a low boiling point can be slowly vaporized at room temperature and penetrated into the polymer, effectively inducing a change in the conformation of the cross-linked polymer chains within the polymer.

[0141] In addition, when the polar solvent is heated during the vapor deposition, the vapor deposition speed can be improved. At this time, the heating temperature is not particularly limited as long as it is a temperature at which the polar solvent can change into vapor, and may be, for example, 30°C to 80°C. General PEO melts at 60°C, but the PEO copolymer modified with the crosslinkable functional group has improved heat resistance when forming a crosslinked structure and can withstand up to 80°C, so the vapor deposition speed can be further increased. In addition, the heating method is not limited to any method that can supply energy to generate vapor. For example, a direct heating method such as a burner or a stove, an indirect heating method such as a heater or a steam pipe, etc. can be used, but the present invention is not limited to these examples.

[0142] When heating above, if the temperature is heated to an excessively high temperature, the solvent may boil above the boiling point of the polar solvent, a structural change of the solvent may occur, or deformation of the polymer may be induced, and there is a disadvantage in that it is difficult to control the evaporation rate of the polar solvent during vapor deposition. Therefore, in order to vapor deposit with a small amount of polar solvent, it may be desirable to perform vapor deposition at a heating temperature within an appropriate range as specified above.

[0143] Meanwhile, the content of polar compounds in the final electrolyte can be controlled by controlling the temperature of the vapor deposition described above, the heating rate, the amount of polar solvent (polar compound) used for evaporation during vapor deposition, and the time and rate of vapor deposition. For example, the content of polar compounds in the electrolyte can be increased by increasing the amount of polar solvent used.

[0144] All-solid-state batteries

[0145] A further embodiment of the invention also relates to an all-solid-state battery comprising the electrolyte, wherein the all-solid-state battery comprises a negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode, wherein the electrolyte is according to the above-described embodiment.

[0146] Specifically, the electrolyte comprises a polymer and a polar compound in which a PEO (polyethylene oxide) polymer having a cross-linking functional group is cross-linked via a cross-linking agent, and a ceramic compound is uniformly dispersed to improve ion conductivity, so that it can be suitable as an electrolyte for an all-solid-state battery.

[0147] Meanwhile, the positive electrode included in the above all-solid-state battery includes a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of the positive electrode current collector.

[0148] The above positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0149] In addition, 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 one element selected from the group consisting of Al, Ga, and In, or two or more of these elements; 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, x+y+z+v=1), Li(LiaMb-a-b'M'b')O 2-c A c (In the above formula, 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2, 0≤c≤0.2; M includes at least one selected from the group consisting of Mn and Ni, Co, Fe, Cr, V, Cu, Zn and Ti; M' is at least one selected from the group consisting of Al, Mg and B, and A is at least one selected from the group consisting of P, F, S and N.) layered compounds or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented by MyO2 (wherein, M=Co, Mn, Al, Cu, Fe, Mg, B or Ga and y=0.01 to 0.3); chemical formula LiMn 2-y M yLithium manganese composite oxides represented by O2 (wherein, M=Co, Ni, Fe, Cr, Zn or Ta, and y=0.01 to 0.1) or Li2Mn3MO8 (wherein, M=Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc., but are not limited thereto.

[0150] In addition, 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, and 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 and electrical characteristics between the positive electrode active materials may be insufficient, and if it is more than 80 wt%, the material transfer resistance may increase.

[0151] In addition, the binder is a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to 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, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepoxychlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, The binder may include at least one selected from the group consisting of cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, 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 at least one selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0152] In addition, the binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer, and specifically, the content of the binder may be 1 wt% or more or 3 wt% or more, and 15 wt% or less or 30 wt% or less. If the content of the binder is less than 1 wt%, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced, and if it exceeds 30 wt%, the adhesive strength may be improved, but the content of the positive electrode active material may be reduced, which may lower the battery capacity.

[0153] In addition, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples thereof include graphite or conductive carbon, and examples thereof 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 crystal structure of graphene or graphite; conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; metal powders such as aluminum powder and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in combination of two or more thereof, but are not necessarily limited thereto.

[0154] 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, and specifically, the content of the conductive material may be 0.5 wt% or more or 1 wt% or more, and 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 effect of improving electrical conductivity or the electrochemical characteristics of the battery may deteriorate, and if it exceeds 30 wt%, the amount of the positive electrode active material may be relatively small, which may lower the capacity and energy density. The method of including the conductive material in the positive electrode is not particularly limited, and a conventional method known in the art, such as coating on the positive electrode active material, may be used.

[0155] In addition, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external conductor and the positive electrode active material layer.

[0156] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the all-solid-state battery. For example, the positive electrode current collector may be copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., or an aluminum-cadmium alloy.

[0157] The positive electrode current collector may have a finely irregular structure on its surface or may employ a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer. Accordingly, the positive electrode current collector may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or non-woven fabric.

[0158] The positive electrode as described above can be manufactured according to a conventional method, and specifically, a composition for forming a positive electrode active material layer prepared by mixing a positive electrode active material, a conductive agent, and a binder in an organic solvent phase is applied and dried on a positive electrode current collector, and optionally, compression-molded on the current collector to improve the electrode density. At this time, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, the binder, and the conductive agent, and that easily evaporates. Specifically, examples thereof include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and methyl pyrrolidone (NMP, N-Methyl-2-Pyrrolidone).

[0159] Meanwhile, the negative electrode included in the above all-solid-state battery includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of the negative electrode current collector.

[0160] The above negative 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.

[0161] The material capable of reversibly inserting or de-inserting lithium ions (Li+) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material capable of reversibly forming a lithium-containing compound by reacting with the lithium ions (Li+) may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of a metal selected from the group consisting of lithium (Li) and 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).

[0162] Preferably, the negative active material may be lithium metal, and specifically, may be in the form of a lithium metal thin film or lithium metal powder.

[0163] 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, and 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 characteristics may not be sufficient, and if it is more than 80 wt%, the material transfer resistance may increase.

[0164] In addition, the binder is as described above in the positive electrode active material layer.

[0165] In addition, the above-described conductive material is as described above in the positive electrode active material layer.

[0166] In addition, the negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. In addition, the negative electrode current collector, like the positive electrode current collector, may be made of various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, etc. having fine irregularities formed on the surface.

[0167] The method for manufacturing the above negative electrode is not particularly limited, and can be manufactured by forming a negative electrode active material layer on the negative electrode current collector using a method for forming a layer or film commonly used in the art. For example, methods such as compression, coating, and deposition can be used. In addition, a case in which a battery is assembled without a lithium thin film on the negative electrode current collector and then a metallic lithium thin film is formed on a metal plate by initial charging is also included in the negative electrode of the present invention.

[0168] Meanwhile, according to an additional embodiment of the invention, a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source are provided.

[0169] At this time, specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0170]

[0171] Hereinafter, preferred embodiments are presented to help understand the invention, but the following embodiments are provided only to make it easier to understand the invention and the invention is not limited thereto.

[0172]

[0173] Example

[0174] Examples 1 to 3 and Comparative Examples 7 to 9: Preparation of electrolyte

[0175] A polyethylene oxide (PEO) copolymer of the following chemical formula 1a was prepared:

[0176] [Chemical Formula 1a]

[0177]

[0178] In the above chemical formula 1a, R1 is -CH2-O-(CH2-CH2-O) k -CH3, R2 is -CH2-O-CH2-CH= CH2, k is 2, the ratio of l:m:n is 85:13:2, and the weight average molecular weight (Mw) of the copolymer was about 2,000,000 g / mol.

[0179] The copolymer of the above chemical formula 1a has an allyl group bonded via a methylene oxide linker as a cross-linking functional group.

[0180] A mixed solution of the polymer and the ceramic compound was prepared by mixing trimethylolpropane trimethacrylate as a crosslinking agent, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound with acetonitrile as a solvent to the above polyethylene oxide copolymer, and then stirring the mixture using a magnetic bar for 24 hours. At this time, the composition of the mixed solution of the polyethylene oxide copolymer and the ceramic compound was as follows: 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 were mixed for 100 parts by weight of the polyethylene oxide copolymer. In addition, the mixing weight ratio of the crosslinking agent was varied to 20 parts by weight (Comparative Example 7), 15 parts by weight (Example 1), 10 parts by weight (Example 2), 8 parts by weight (Example 3), 5 parts by weight (Comparative Example 8), and 0 parts by weight (Comparative Example 9) with respect to 100 parts by weight of the polyethylene oxide copolymer.

[0181] Acetonitrile solvent was used so that the concentration of the polymer polyethylene oxide copolymer contained in the mixed solution thus manufactured was 11.1 wt%, and the concentration of the polymer polyethylene oxide copolymer and the ceramic compound was 14.9 wt%.

[0182] After casting the above-prepared mixed solution onto the lower substrate of the coin cell, it was first dried at room temperature for 12 hours, and then secondarily dried in a vacuum oven at 100°C for 12 hours to produce an electrolyte film with a thickness of 200 μm.

[0183] The above electrolyte film was attached to the chamber top, and the lower part of the chamber was filled with 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 interior of the electrolyte film attached to the upper part of the chamber. Through this, EMC was vapor-deposited onto the electrolyte film to produce an electrolyte.

[0184]

[0185] Comparative Examples 1 to 6:

[0186] An electrolyte was prepared in the same manner as in Examples 1 to 3 and Comparative Examples 7 to 9, except that the step of vapor deposition of the EMC solvent in Example 1 was not performed.

[0187] At this time, during the production of Comparative Examples 1 to 6, the mixing weight ratio of the crosslinking agent to 100 parts by weight of the polyethylene oxide copolymer was varied to 20 parts by weight (Comparative Example 1), 15 parts by weight (Comparative Example 2), 10 parts by weight (Comparative Example 3), 8 parts by weight (Comparative Example 4), 5 parts by weight (Comparative Example 5), and 0 parts by weight (Comparative Example 6), respectively.

[0188]

[0189] Comparative Examples 10 to 12: Preparation of electrolyte (including a large amount of polar solvent)

[0190] An electrolyte film was manufactured using the same method as in Examples 1 to 3 above.

[0191] An electrolyte was prepared in the same manner as in Examples 1 to 3, except that the EMC solvent was directly injected as a liquid solvent rather than vapor-deposited. The EMC solvent was directly injected so that the content was 12 wt% relative to the total weight of the prepared electrolyte.

[0192]

[0193] Experimental example

[0194] Experimental Example 1: Measurement of the content of polar compounds

[0195] The content of polar compounds can be measured by monitoring the weight of the liquid phase that evaporates over time while heating the solid electrolyte sample using a balance. For example, the weight of the liquid phase that evaporates over time can be measured by heating the sample from a temperature of 55°C under elevated temperature using a heating-type electronic balance (AND MS-70). When the amount of polar compounds that evaporate over time reaches saturation, the saturation amount at that time is regarded as the total amount of polar compounds contained within the solid electrolyte. In the examples and comparative examples, the polar compound was ethyl methyl carbonate (EMC; boiling point: about 101°C), and the heating under elevated temperature for measuring the content of the polar compound was conducted to about 110°C.

[0196] Table 1 below shows the results of measurements of the content of EMC vapor deposited (or included) in the electrolyte.

[0197] EMC content (wt%) relative to total electrolyte weight Examples 1 to 3 1.2 Comparative Examples 1 to 6 0 Comparative Examples 7 to 9 1.2 Comparative Examples 10 to 12 12

[0198]

[0199] Experimental Example 2: Measuring the ionic conductivity of electrolytes

[0200] In order to measure the ionic conductivity of the electrolyte manufactured in the examples and comparative examples, 1.7671 cm 2 After forming the electrolyte on the lower substrate of a coin cell of a size, a coin cell for measuring ionic conductivity was manufactured using SUS as an inactive electrode (blocking electrode).

[0201] The resistance was measured at 25°C using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) 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 Equation 1 below.

[0202] [Formula 1]

[0203]

[0204] In the above equation 1, 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 (㎛), and A is the area of ​​the electrolyte (cm 2 ) means. The electrolyte sample above has L=200㎛ and A=1.7671cm 2 It was used.

[0205] The results of the ionic conductivity evaluation of Examples 1 to 3 and Comparative Examples 1 to 9 measured as above are shown in Fig. 1.

[0206] Referring to Fig. 1, Comparative Examples 1 to 6 were manufactured without vapor deposition of a polar compound (EMC), and were confirmed to exhibit lower ionic conductivity compared to the examples.

[0207] In addition, while Examples 1 to 3, in which the weight ratio of the crosslinking agent was optimized, exhibited excellent ionic conductivity, Comparative Examples 8 and 9, in which the weight ratio of the crosslinking agent was excessively low, were confirmed to be unable to measure the ionic conductivity itself, and Comparative Example 7, in which the weight ratio of the crosslinking agent was excessively high, was also confirmed to exhibit lower ionic conductivity than the Examples.

[0208] Additionally, the ionic conductivity of Comparative Examples 10 to 12, in which a significant amount of polar solvent was injected in the liquid phase, was measured in the same manner, and compared with Examples 1 to 3, the results are shown in Table 2 below.

[0209] Ionic Conductivity (@25℃; mS / cm) Example 10.988 Example 21.768 Example 32.263 Comparative Example 100.391 Comparative Example 110.423 Comparative Example 12 Not measured

[0210] * “Not measured”: The cross-linking structure of the electrolyte itself collapsed, making it impossible to measure the ionic conductivity. Referring to Table 2 above, it was confirmed that the electrolyte of the example exhibited excellent ionic conductivity even compared to Comparative Examples 10 to 12, which had a very high content of polar compounds (polar solvents). This is presumed to be because, as the polar compounds in the electrolyte of the example were vapor-deposited, they were included or combined in a gaseous state in the solid electrolyte. In addition, in Comparative Examples 10 to 12, as a large amount of polar solvent was directly injected into the electrolyte, whose mechanical properties were weakened due to a decrease in the degree of cross-linking, the increase in ionic conductivity was reduced due to an increase in the structural instability of the electrolyte, or it was confirmed that the ionic conductivity could not be measured due to an internal short circuit.

Claims

1. A polymer including a PEO (polyethylene oxide) polymer having a cross-linking functional group; a ceramic compound; and an electrolyte including a polar compound, At least a portion of the above cross-linking functional groups form cross-links via a cross-linking agent, so that the polymer forms a three-dimensional network structure, The polar compound is included in the three-dimensional network structure or is bonded on the polymer chain, and is included in an amount of 0.1 wt% or more and less than 10 wt% based on the total weight of the electrolyte, An electrolyte in which the crosslinking agent is included in a weight ratio of 0.07 to 0.19 with respect to the weight of the PEO polymer including the crosslinking functional group.

2. An electrolyte in the first paragraph, wherein at least a portion of the polar compound is dispersed between polymer chains forming the three-dimensional network structure in a vapor-deposited gaseous state, or is adsorbed or bound to the surface or interior of the polymer chains.

3. In the first paragraph, the crosslinking agent is an electrolyte comprising a multifunctional compound having multiple 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 hydroxyl group, an epoxy functional group, and an allyl group.

4. In the first paragraph, the cross-linking functional group is bonded to the PEO polymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (provided that the alkylene linker having 0 carbon atoms represents a single bond), An electrolyte 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.

5. An electrolyte further comprising a lithium salt according to claim 1.

6. An electrolyte in the fifth paragraph, wherein the lithium salt is included in an amount of 25 to 45 parts by weight based on 100 parts by weight of the PEO polymer.

7. In the first paragraph, the PEO (polyethylene oxide) polymer is an electrolyte that is a copolymer containing repeating units of the following chemical formulas 1 to 3: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3 represents, k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms, R2 represents a substituent in which at least one cross-linking 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 is bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (provided that the alkylene linker having 0 carbon atoms represents a single bond), l, m and n are the repetition numbers of the repetition unit, l and n are each independently an integer from 1 to 100000, and m is an integer from 0 to 100000.

8. In the first paragraph, the PEO polymer is an electrolyte having a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol.

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

10. An electrolyte according to 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.

11. In the first paragraph, the ceramic compound is an electrolyte comprising an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate.

12. In the first paragraph, the ceramic compound is an electrolyte comprising at least one oxide-based solid electrolyte selected from the group consisting of a lithium-lanthanum-zirconium oxide (LLZO) compound, a lithium-silicon titanium phosphate (LSTP) compound, a lithium-lanthanum-titanium oxide (LLTO) compound, a lithium-aluminum-titanium phosphate (LATP) compound, a lithium-aluminum-germanium phosphate (LAGP) compound, and a lithium-lanthanum-zirconium-titanium oxide (LLZTO) compound.

13. An electrolyte in the first paragraph, wherein the ceramic compound is included in an amount of 10 to 100 parts by weight based on 100 parts by weight of the PEO polymer.

14. An electrolyte according to claim 1, wherein the ceramic compound is included in the form of particles having a diameter of 100 nm to 1000 nm.

15. An all-solid-state battery comprising an electrolyte layer including the electrolyte of any one of claims 1 to 14.

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