Solid-state battery

Abstract

The present invention relates to a solid-state battery. The solid-state battery comprises: a positive electrode; a negative electrode; and an electrolyte layer interposed between the positive electrode and the negative electrode, the electrolyte layer comprising: a polymer including a polyethylene oxide (PEO)-based copolymer having cross-linkable functional groups, of which at least a portion form crosslinks; a ceramic compound; and a polar compound, wherein the polar compound is dispersed in or linked onto the polymer, and the positive electrode comprises: a positive electrode active material; and a binder including a PEO-based copolymer having cross-linkable functional groups.

Description

solid state batteries

[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, and Korean Patent Application No. 10-2024-0123904, filed September 11, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a solid battery including a solid electrolyte layer.

[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 (solid-state batteries) utilizing 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, these batteries 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] Conventional hybrid (composite) solid electrolytes, such as these, are manufactured by dispersing inorganic powders such as oxide ceramics in a polymer matrix. Compared to existing liquid electrolytes, they have high ignition and combustion stability, and compared to polymer solid electrolytes, they have the advantage of high ionic conductivity. However, there has been a difficulty in that basic prerequisites such as improving the dispersibility of oxide ceramic particles within the polymer matrix and optimizing the physical properties of the polymer matrix used must be satisfied. In particular, when a highly crystalline polymer such as polyethylene oxide (PEO) is used as the matrix, there has been a problem in that it is difficult to manufacture a composite solid electrolyte with improved ionic conductivity. In other words, 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. Therefore, there has been a limit to improving the ionic conductivity of the polymer solid electrolyte.

[0008] In particular, conventional electrolytes have difficulty achieving a certain level of ionic conductivity at room temperature, which has limited the development of solid-state batteries that can be operated at room temperature.

[0009] Accordingly, the present invention provides a solid battery including a solid electrolyte exhibiting excellent ionic conductivity.

[0010] According to one embodiment of the invention, a solid battery comprising: a positive electrode; a negative electrode; and an electrolyte layer interposed between the positive electrode and the negative electrode, wherein the electrolyte layer comprises: a polymer including a PEO (polyethylene oxide) copolymer having a cross-linking functional group at least part of which forms a cross-linking bond; a ceramic compound; and a polar compound, wherein the polar compound is dispersed or bonded on the polymer;

[0011] The above positive electrode provides a solid battery including a positive electrode active material and a binder including a PEO copolymer having a cross-linking functional group.

[0012] In these solid-state batteries, the polar compound may be dispersed between the polymer chains forming the cross-linked bonds, or may be adsorbed or bound to the surface or interior of the polymer chains.

[0013] In addition, at least some of the cross-linkable functional groups can form cross-links with each other via a cross-linking agent, and the cross-linkable functional groups are bonded to the PEO copolymer 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).

[0014] It can be 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.

[0015] In a more specific embodiment, the PEO (polyethylene oxide) copolymer may be a copolymer including repeating units of the following chemical formulas 1 to 3:

[0016] [Chemical Formula 1]

[0017]

[0018] [Chemical Formula 2]

[0019]

[0020] [Chemical Formula 3]

[0021]

[0022] 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,

[0023] 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).

[0024] 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.

[0025] Meanwhile, in the solid-state battery of the above embodiment, at least one of the electrolyte layer or the positive electrode may further include a lithium salt.

[0026] Additionally, in the solid battery, the content of the polar compound may be 0.1 wt% or more and less than 10 wt% based on the total weight of the electrolyte layer, and the polar compound may include at least one selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0027] Additionally, the ceramic compound may include an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate.

[0028] Meanwhile, when the above-mentioned anode is rolled on both sides using a roll, it can exhibit characteristics that satisfy the thickness strain defined by the following equation 2:

[0029] [Formula 2]

[0030]

[0031] In the above equation 2, δ0 and d0 represent the initial roll gap and the initial thickness of the anode before rolling, and δ and d represent the roll gap and the thickness of the anode during rolling, and C and n are constants determined by regression analysis.

[0032] Additionally, in the solid battery, the negative electrode may include a lithium metal layer.

[0033] A solid-state battery according to one embodiment of the invention comprises a predetermined electrolyte layer manufactured by vapor deposition of a polar compound, for example. This electrolyte layer can exhibit improved ionic conductivity by improving the mobility of polymer chains and uniformly distributing ceramic particles within the electrolyte while maintaining the inherent structural properties of the polymer without deformation or destruction of the polymer chains.

[0034] In addition, the electrolyte can improve the ionic conductivity and mechanical properties of the polymer solid electrolyte by including a trace amount of polar compound.

[0035] In combination with a composite electrolyte layer exhibiting such excellent ionic conductivity, a positive electrode to which a binder of the same type as the composite electrolyte layer is applied, a solid battery of one embodiment exhibits excellent charge / discharge characteristics at room temperature and high temperature, and can exhibit high ionic conductivity and mechanical properties.

[0036] Figure 1 shows the activation energy and log(σ) of the electrolyte layer according to the absolute temperature included in Example 1 and Comparative Example 1. i ) is a graph showing the results of the evaluation.

[0037] Figure 2 is a graph showing the degree of thickness deformation evaluated when the anode included in Example 1 was rolled using a roll.

[0038] Figure 3 is a graph showing the results of a charge / discharge test at room temperature (25°C) of the solid battery of Example 1.

[0039] Figure 4 is a graph showing the results of a charge / discharge test at room temperature (25°C) and high temperature (60°C) of the solid battery of Comparative Example 1.

[0040] Hereinafter, specific implementation examples of the invention will be described in more detail to help understand the invention.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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, when the polar compound is deposited in a vaporous state, it means that the polar solvent, etc. 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 same. 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.”

[0045] In this specification, the term “solid-state battery” may be interpreted to encompass not only a so-called all-solid-state battery that does not contain any liquid in the entire battery structure including the electrolyte (layer), but also a case in which, depending on the storage or operating conditions of the electrolyte and / or the battery, a polar compound vapor-deposited on the electrolyte is locally or temporarily liquefied, thereby containing a small amount of liquid.

[0046]

[0047] Meanwhile, in the past, in order to improve the ionic conductivity of solid electrolytes, electrolytes were manufactured by dispersing ceramic compounds such as oxides in a polymer matrix. However, these electrolytes had a problem in that the ionic conductivity was reduced when the oxide-based ceramic particles in the polymer matrix were unevenly distributed or when a polymer with high crystallinity such as polyethylene oxide was used as the polymer.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 and a ceramic compound cross-linked with a PEO (polyethylene oxide) copolymer modified with a cross-linking functional group. The electrolyte thus manufactured comprises a polymer comprising 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 to the polymer chain.

[0052] 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.

[0053] 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.

[0054] 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. As a result, the electrolyte has a large content of polar solvent or electrolyte that is always in a liquid state, resulting in the characteristics of a semi-solid battery. 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.

[0055] The content of the polar compound contained in the electrolyte 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 polar compound starts to evaporate at a temperature, for example, 40°C or higher, or 50°C or higher, while heating under elevated temperature to a temperature between the boiling point and 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 elevated temperature elapses, and this can be regarded as the total amount of the polar compound contained in the electrolyte.

[0056] 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, and this will also be apparent from the examples described later.

[0057] Meanwhile, the electrolyte can exhibit better ionic conductivity due to the ceramic compound uniformly dispersed within the three-dimensional network structure.

[0058] Therefore, the electrolyte exhibits improved ionic conductivity without substantially containing a liquid polar solvent or electrolyte, thereby contributing to the development of a solid battery with excellent physical properties.

[0059] Accordingly, a solid-state battery according to one embodiment of the invention includes the above-described electrolyte and a positive electrode preferably combined therewith, thereby exhibiting excellent ionic conductivity and other characteristics.

[0060] In a specific example, the polar compound may be dispersed between polymer chains that form a three-dimensional network structure by cross-linking, for example, in a vapor-deposited gaseous state, or may be adsorbed or bound to the surface or interior of the polymer chains.

[0061] 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 that the polar compound has a state similar to an electrolyte in which vapor deposition has occurred.

[0062] 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 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.

[0063] Meanwhile, in the electrolyte, the cross-linkable functional group may be directly bonded to the main chain of the PEO copolymer, 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.

[0064] 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 can be more easily controlled.

[0065] The above cross-linking functional group refers to a functional group that can form a cross-linking bond between cross-linking functional groups, and / or 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.

[0066] In a more specific embodiment, the PEO copolymer including the cross-linking functional group may be a copolymer including repeating units of the following chemical formulae 1 to 3:

[0067] [Chemical Formula 1]

[0068]

[0069] [Chemical Formula 2]

[0070]

[0071] [Chemical Formula 3]

[0072]

[0073] 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,

[0074] 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).

[0075] 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.

[0076] 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 having improved ionic conductivity can be provided by including or combining a polar compound within the three-dimensional network structure.

[0077] In addition, it is obvious that the PEO copolymer may include two or more repeating units of chemical formula 3 in which R2 is a different cross-linking functional group, and may also include one or more repeating units of chemical formula 2.

[0078] If the above l, m and n are each too small, it is difficult to form a polymer due to the small molecular weight, and if 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, if 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.

[0079] Meanwhile, in this specification, “hydroxyl group” refers to an -OH group.

[0080] In this specification, “carboxyl group” refers to a -COOH group.

[0081] In this specification, “isocyanate group” refers to a -N=C=O group.

[0082] In this specification, “nitro group” refers to a -NO2 group.

[0083] In this specification, “cyano group” refers to a -CN group.

[0084] 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.

[0085] 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.

[0086] In this specification, “allyl group” refers to a -CH2-CH=CH2 group.

[0087] The weight average molecular weight (Mw) of the above-described cross-linked PEO copolymer may be 100,000 g / mol to 4,000,000 g / mol, and 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 copolymer 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 copolymer 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.

[0088] In addition, if the number of repetitions of the repeating unit of chemical formula 3 containing a cross-linking functional group is excessively large, the degree of cross-linking may increase excessively, which may reduce the mobility of the polymer chain and decrease the ionic conductivity of the electrolyte.

[0089] Additionally, the copolymer may be a random copolymer or a block copolymer.

[0090] 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.

[0091] The above polar compound is a gas molecule of a polar solvent used in a vapor deposition process. 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 the polar compound being bound to the polymer chain or being included in a form dispersed in the internal space between the polymer chains, the ionic conductivity of the final manufactured electrolyte can be improved.

[0092] 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.

[0093] 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 copolymer, 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.

[0094] Additionally, the polar compound may include at least one selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0095] 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.

[0096] 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, 1 wt% or more, 2 wt% or more, 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%.

[0097] In one embodiment of the invention, the electrolyte may comprise cross-linking between cross-linking functional groups. Furthermore, the electrolyte may further comprise a cross-linking agent, thereby further comprising cross-linking between the cross-linking agent and the cross-linking functional groups. For example, at least a portion of the cross-linking functional groups may form cross-linking bonds with each other via the cross-linking agent, thereby forming the three-dimensional network structure described above.

[0098] The above cross-linking bond may be a urethane bond, an ester bond, a hydrogen bond, a bond formed by a radical polymerization reaction by a vinyl group at the end of an allyl group (-CH2-CH=CH2), etc., but is not limited to these examples.

[0099] In addition, when a crosslinking agent is added in the manufacturing process of the electrolyte, 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.

[0100] The above cross-linking agent is not particularly limited as long as it is a multifunctional cross-linking agent capable of forming a cross-linking bond with the above cross-linking functional group. For 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 methacrylate. 3-(acryloyloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acryloylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methylacryloxypropyl trimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene,Ethylene glycol maleic rosinate acrylate, glycidilmethacrylate, hydroxyquinoline, iphenyldiethoxysilane, maleic rosin glycol acrylate, methylene bisacrylamide, N,N'-1,4-phenylenediacrylamine, N,O-bisacryloyl-phenylalaninol, N,O-bismethacryloyl ethanolamine, pentaerythritol triacrylate, At least one polyfunctional crosslinking agent selected from the group consisting of phenyltrimethoxy silane, tetramethoxysilane, tetramethylene, tetraethoxysilane, and triallyl isocyanurate, for example, a polyfunctional compound having two or more functionalities.

[0101] In addition, the crosslinking agent may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the PEO copolymer including a crosslinking functional group included in the polymer mixture. If the content of the crosslinking agent is less than 1 part by weight, crosslinking with the crosslinking functional group may not be sufficiently formed, and if it exceeds 30 parts by weight, crosslinking may be excessively formed, which may reduce the mobility of the polymer chain and thus lower ion conductivity.

[0102] 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.

[0103] 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.

[0104] 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 polymer mixture, 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] The ceramic compound may be included in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, or 20 to 50 parts by weight, or 25 to 45 parts by weight, based on 100 parts by weight of the polymer mixture.

[0112] 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 overall mechanical properties of the electrolyte may also be insufficient.

[0113] 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.

[0114] Meanwhile, the electrolyte described above can exhibit excellent ionic conductivity. For example, the electrolyte can exhibit excellent ionic conductivity of 0.6 mS / cm or more, or 0.9 mS / cm or more, or 0.95 mS / cm or more, or 0.95 mS / cm to 1.50 mS / cm, measured at room temperature of about 25°C.

[0115] This ionic conductivity can be calculated from the resistance (Ω) of the electrolyte measured by an electrochemical impedance spectrometer at a constant temperature such as room temperature, according to the following equation 4:

[0116] [Formula 4]

[0117]

[0118] In the above equation 4, 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.

[0119] Meanwhile, the electrolyte described above can exhibit a characteristic in which the temperature-dependent activation energy deviation (△Ea) defined by the following equation 1 is 0.03 eV or less, or 0.005 to 0.025 eV:

[0120] [Formula 1]

[0121] ΔE a = E a LT - E a HT

[0122] In the above equation 1, E a LT is the activation energy of the electrolyte layer at -40°C to 10°C, and E a HT is the activation energy of the electrolyte layer at 10℃ to 80℃, and ΔE a represents the temperature-dependent activation energy deviation defined as the difference between the two activation energies above.

[0123] At this time, the activation energy deviation can be calculated from the ionic conductivity of the electrolyte measured by absolute temperature. More specifically, the ionic conductivity by temperature (σ i ), based on the measurement results of log(σ i ) and 1000 / T (T is the relationship between the absolute temperature at which the ionic conductivity was measured) can be fitted to the Arrhenius equation of Equation 3 below to derive the activation energy Ea corresponding to the slope, from which E of Equation 1 above can be derived. a LT , E a HT and ΔE a can be produced respectively.

[0124] [Formula 3]

[0125]

[0126] In the above equation, σ i,0 represents the maximum ionic conductivity of the electrolyte layer, and σ irepresents the ionic conductivity of the electrolyte layer measured at absolute temperature T, Ea represents the activation energy of the electrolyte layer at absolute temperature T, and R represents the gas constant.

[0127] From this low activation energy deviation, it can be confirmed that the above-described electrolyte exhibits excellent ionic conductivity and electrochemical properties without significant deviation despite temperature changes.

[0128] The method for manufacturing the above-described electrolyte may include a step of mixing a PEO copolymer containing the cross-linking functional group and a ceramic compound, and then performing a cross-linking reaction on the PEO copolymer contained in the mixture; and a step of vapor-depositing a polar solvent on the mixture containing the cross-linked polymer.

[0129] The description of the PEO copolymer containing the above cross-linking functional group is as described above.

[0130] In this manufacturing method, first, a PEO copolymer containing a cross-linking functional group and a ceramic compound are mixed, and then a cross-linking reaction is performed on the PEO copolymer contained in the mixture, thereby manufacturing a polymer forming the three-dimensional network structure described above.

[0131] The above crosslinking reaction can proceed in the presence of at least one additional agent selected from the group consisting of a crosslinking agent and an initiator.

[0132] Additionally, a lithium salt may be added together in the mixing step and / or cross-linking reaction step for electrolyte formation.

[0133] 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.

[0134] The above crosslinking reaction can be formed in the process of forming a coating film by applying a solution containing the crosslinked PEO copolymer and a ceramic compound, etc. onto a substrate and then drying the solution.

[0135] Specifically, the mixed solution can be prepared by mixing the cross-linked PEO copolymer and the ceramic compound in a solvent, and further, can be prepared by mixing a cross-linking agent, an initiator, and / or a lithium salt together. In addition, a mixed solution or suspension can be prepared by first preparing a solution containing the cross-linked PEO copolymer, a cross-linking agent, an initiator, and / or a lithium salt, and then adding a ceramic compound.

[0136] The solvent is not particularly limited as long as it is a solvent that can mix the cross-linked PEO copolymer, cross-linking 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 cross-links, and are distinguished from polar solvents included in liquid electrolytes, etc., and are completely removed by drying, etc. after cross-linking.

[0137] 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 the cross-linked PEO copolymer. 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 onto 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.

[0138] 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 (Steel Use Stainless), 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.

[0139] 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.

[0140] 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.

[0141] Additionally, the cross-linking agent may form a bond with the cross-linking functional group. The type of the cross-linking agent, the content of the cross-linking agent, and the type of bond with the cross-linking functional group are as described above.

[0142] 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.

[0143] 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).

[0144] 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 crosslinked PEO copolymer including the crosslinkable functional group, and when used in the above range, it can induce a radical polymerization reaction between the crosslinkable functional groups, thereby enabling efficient formation of crosslinks.

[0145] In addition, the content and type of the lithium salt are as described above.

[0146] In the above vapor deposition step, the crosslinked resultant can be vapor deposited by exposing it to a vaporized polar compound (polar solvent).

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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, which will be clearly seen in the following examples.

[0152] solid state batteries

[0153] Embodiments of the invention also provide a solid-state battery comprising the electrolyte. Such a solid-state battery comprises, for example, a positive electrode including a positive electrode active material layer; a negative electrode; and a solid electrolyte layer interposed between the positive electrode and the negative electrode, wherein the solid electrolyte layer may comprise the electrolyte described above.

[0154] In such a solid-state battery, the positive electrode active material layer may include a positive electrode active material and a binder including a PEO copolymer having a cross-linking functional group. In a more specific example, the PEO copolymer having a cross-linking functional group may be the same as or identical to that included in the electrolyte layer described above. In addition, at least a portion of the cross-linking functional groups of the PEO copolymer may form cross-links, similarly to those included in the electrolyte layer.

[0155] Since the binder of the positive electrode active material layer includes such a cross-linked PEO copolymer, the interfacial properties and bonding properties between the positive electrode active material layer and the solid electrolyte layer can be improved. Accordingly, the solid-state battery of the above embodiment can exhibit superior ionic conductivity and mechanical properties.

[0156] In addition, due to the type of binder of these positive electrode active materials, it is easier to control the thickness of the positive electrode by adjusting the process conditions during the rolling process of the positive electrode, and thus excellent processability can be exhibited.

[0157] More specifically, the positive electrode can be formed, for example, by applying a layer of positive electrode active material on a positive electrode current collector and then rolling it. At this time, when the positive electrode is rolled on both sides using a roll, the positive electrode can satisfy the thickness strain defined by Equation 2 below.

[0158] [Formula 2]

[0159]

[0160] In the above equation 2, δ0 and d0 represent the initial roll gap and the initial thickness of the anode before rolling, and δ and d represent the roll gap and the thickness of the anode during rolling, and C and n are constants determined by regression analysis.

[0161] For reference, the above C and n can be used as criteria for classifying the characteristics of electrode manufacturing materials based on their inherent material properties. Based on the above formula, it is possible to manufacture an anode with a constant porosity and elastic recovery rate, which has the advantage of minimizing errors caused by the anode when evaluating solid-state battery performance and identifying only the influence of the properties of the solid electrolyte.

[0162] The characteristics of this equation 2 can indicate that, when the rolling process is performed by a roll-to-roll process, the thickness ratio of the positive electrode is approximately inversely proportional to the gap ratio between the rolling rolls. Accordingly, it is easy to form a positive electrode and a positive electrode active material layer of a desired thickness by the rolling process, and excellent processability can be exhibited.

[0163] Meanwhile, the positive electrode active material layer may further include a conductive material in addition to the positive electrode active material and binder.

[0164] 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-yNi-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 y Lithium 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.

[0165] In addition, the positive electrode active material may be included in an amount of 40 to 90 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 90 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 properties between the positive electrode active materials may be insufficient, and if it is more than 90 wt%, the material transfer resistance may increase.

[0166] In addition, the binder may include the above-described cross-linkable PEO copolymer as a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to the current collector. However, in addition to this copolymer, a general binder may be further included.

[0167] Examples of such additional binders are not particularly limited and include, for example, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorinated 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, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate It may include at least one selected from the group consisting of 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.

[0168] However, in a more suitable example, the binder may include as a main component a PEO copolymer having the same or identical cross-linking functional group as that included in the electrolyte. In this way, since the positive electrode active material layer includes the same binder as the solid electrolyte layer, the solid battery may exhibit excellent mechanical properties along with excellent charge / discharge characteristics and ionic conductivity. In a more specific example, the PEO copolymer having the cross-linking functional group may be included in a proportion of 60 wt% or more, or 80 wt% or more, or 90 to 100 wt% of the total binder.

[0169] 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.

[0170] In addition, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the solid-state battery and has excellent electrical conductivity without causing chemical changes in the battery. 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.

[0171] 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.

[0172] 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.

[0173] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the 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.

[0174] 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.

[0175] 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, can be manufactured. 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).

[0176] Meanwhile, the negative electrode included in the solid 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.

[0177] The above negative active material is lithium (Li) + ) can be reversibly intercalated or deintercalated, a material that can reversibly form a lithium-containing compound by reacting with lithium ions, or a lithium metal or lithium alloy. Among these, by making the negative electrode include a lithium metal layer, the solid-state battery can exhibit better energy density and conductivity.

[0178] The above lithium ion (Li + ) can be reversibly inserted or removed, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The lithium ion (Li +) can be, for example, tin oxide, titanium nitrate or silicon. The lithium alloy can 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).

[0179] 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.

[0180] 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.

[0181] In addition, the binder is as described above in the positive electrode active material layer.

[0182] In addition, the above-described conductive material is as described above in the positive electrode active material layer.

[0183] 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.

[0184] 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 through initial charging is also included in the negative electrode of the present invention.

[0185] Meanwhile, according to an additional embodiment of the invention, a battery module including the solid 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.

[0186] 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.

[0187]

[0188] 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.

[0189]

[0190] Example

[0191] Example 1: Preparation of electrolyte and solid-state battery

[0192] Step 1) Manufacturing of polymers containing copolymers

[0193] A polyethylene oxide (PEO) copolymer of the following chemical formula 1a was prepared:

[0194] [Chemical Formula 1a]

[0195]

[0196] 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.

[0197] The copolymer of the above chemical formula 1a has an allyl group bonded via a methylene oxide linker as a cross-linking functional group.

[0198] A mixed solution of polymer and 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 the above polyethylene oxide copolymer using acetonitrile as a solvent, 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 such that 20 parts by weight of trimethylolpropane trimethacrylate as a crosslinking agent, 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, and the concentration of the polyethylene oxide copolymer as a polymer contained in the mixed solution was 11.1% by weight, and the concentration of the polyethylene oxide copolymer as a polymer and the ceramic compound was 14.9% by weight, using acetonitrile as a solvent.

[0199] After casting the above-prepared mixed solution onto the lower substrate of the coin cell, it was dried for the first time at room temperature for 12 hours, and then dried for the second time in a vacuum oven at 100°C for 12 hours to produce an electrolyte film with a thickness of 200 μm.

[0200] Step 2) Preparation of electrolyte

[0201] The above polymer was attached to the upper plate of the chamber, 50 μl of ethyl methyl carbonate (EMC) solvent was filled in the lower part of the chamber, and then naturally evaporated at room temperature for 72 hours. The EMC vapor was introduced into the interior of the polymer attached to the upper part of the chamber and deposited on the polymer to produce an electrolyte.

[0202] Step 3) Manufacturing of solid-state batteries (electrode assemblies)

[0203] NCMA (LiNi 0.85 Co 0.05 Mn 0.08 Al 0.02 O2) Positive electrode active material particles (particle size: 5-10 ㎛, LG CHEM, Republic of Korea), superconductive carbon (C-65) conductive agent, cross-linked PEO copolymer of chemical formula 1a used in step 1, LiTFSI were added in a weight ratio of 77.6:3:14.2:5.2 using acetonitrile as a solvent, and stirred at room temperature for 5 times at 1500 rpm / 3 min using a paste mixer. The prepared mixed solution was solution-casted on aluminum foil, and then dried at room temperature for 6 hours and then dried at 100°C for 12 hours to prepare a 60 ㎛ thick positive electrode film. The positive electrode film had a density of 6.712 mg / cm 2 After mass loading, the composite solid electrolyte manufactured above was used as an electrolyte film, and lithium metal foil (300 μm) was used as a negative electrode, and then laminated in a sandwich type to manufacture a coin cell.

[0204]

[0205] Example 2: Preparation of electrolyte and solid-state battery

[0206] In step 2) of the above Example 1, the polymer was attached to the upper plate of the chamber, 300 μl of ethyl methyl carbonate (EMC) solvent was filled in the lower part of the chamber, and then naturally evaporated at room temperature for 72 hours to introduce EMC vapor into the interior of the polymer attached to the upper part of the chamber and deposit it on the polymer to prepare an electrolyte.

[0207] The remaining process was carried out in the same manner as in Example 1, and an electrolyte and a solid-state battery were manufactured.

[0208]

[0209] Comparative example:

[0210] Comparative Example 1: Manufacturing of electrolyte and solid-state battery

[0211] An electrolyte and a solid-state battery were manufactured in the same manner as in Example 1, except that the step of vapor deposition of the EMC solvent in step 2) of Example 1 was not performed.

[0212]

[0213] Comparative Example 2: Electrolyte and battery manufacturing (including a large amount of polar solvent)

[0214] In step 2) of Example 1, an electrolyte was prepared in the same manner as in Example 1, 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.

[0215] The remaining process was carried out in the same manner as in Example 1 to manufacture the electrolyte and battery.

[0216]

[0217] Experimental example

[0218] Experimental Example 1: Measurement of the content of polar compounds

[0219] 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.

[0220] Table 1 below shows the results of measurements of the content of EMC vapor deposited (or included) in the electrolyte.

[0221] EMC content (weight %) relative to total electrolyte weight Example 11.2 Example 26 Comparative Example 10 Comparative Example 212

[0222]

[0223] Experimental Example 2: Measuring the ionic conductivity of electrolytes

[0224] 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 (Steel Use Stainless) as an inactive electrode (blocking electrode).

[0225] 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 4 below.

[0226] [Formula 4]

[0227]

[0228] In the above equation 4, 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 has L=200㎛ and A=1.7671cm 2 It was used.

[0229]

[0230] Experimental Example 3: Measurement of activation energy at different temperatures in the electrolyte layer.

[0231] Temperature-dependent ionic conductivity of electrolyte films (σ i ) was measured using the same method as Experimental Example 2. Based on the measurement results, log(σ i ) and 1000 / T (T is the absolute temperature at which the ionic conductivity was measured), the relationship between the absolute temperature and the ionic conductivity was fitted to the Arrhenius equation in Equation 3 below, and Ea corresponding to the slope was derived.

[0232] [Formula 3]

[0233]

[0234] In the above equation, σ i,0 represents the maximum ionic conductivity of the electrolyte layer, and σ i represents the ionic conductivity of the electrolyte layer measured at absolute temperature T, Ea represents the activation energy of the electrolyte layer at absolute temperature T, and R represents the gas constant.

[0235]

[0236] Experimental Example 4: Evaluation of Thickness Strain During Rolling for the Anode

[0237] In the examples, a 60 μm thick positive electrode film was passed through a roll-to-roll rolling mill and rolled to reduce the porosity within the electrode. The gap between the nip rolls of the rolling mill was gradually reduced, and the thickness of the positive electrode film according to each gap was measured, and the ratio of the thickness of the positive electrode film according to the roll gap to the film thickness before rolling was calculated. The ratio of the gap between the rolls thus calculated vs. the thickness ratio of the positive electrode film was subjected to regression analysis to determine the values ​​of C and n in Equation 2 below.

[0238] [Formula 2]

[0239]

[0240] In the above equation 2, δ0 and d0 represent the initial roll gap and the initial thickness of the anode before rolling, and δ and d represent the roll gap and the thickness of the anode during rolling, and C and n are constants determined by regression analysis. These C and n are inherent properties of the material and can be used as criteria for classifying the characteristics of electrode manufacturing materials. Based on the above equation, it is possible to manufacture anodes with a constant porosity and elastic recovery rate, which has the advantage of minimizing errors caused by the anode when evaluating the performance of solid batteries and identifying only the influence of the properties of the solid electrolyte.

[0241]

[0242] Experimental Example 5: Charge / Discharge Test for All-Solid-State Battery

[0243] In order to evaluate the galvanostatic cycling characteristics of the solid-state batteries manufactured in the above Examples and Comparative Examples, charge and discharge tests were performed on the solid-state batteries in the voltage range of 3.0 V to 4.25 V using a TOSCAT charge and discharge tester (manufactured by TOYO Systems Co., Ltd.). For the solid-state batteries manufactured in the Examples, charge and discharge tests were performed at a charge and discharge rate of 0.03 C at room temperature (25 ° C). After reaching a cut-off voltage of 4.25 V, CV (constant voltage) charging was additionally performed under a cut-off current condition of 0.01 C. In addition, charge and discharge tests were performed at a charge and discharge rate of 0.03 C at 25 ° C and 60 ° C, respectively, for the solid-state batteries including the solid electrolyte of the Comparative Examples.

[0244]

[0245] First, the results of the ionic conductivity evaluation for each electrolyte of the examples and comparative examples measured in the above examples are summarized and shown in Table 2 below.

[0246] Ionic Conductivity (@25℃; mS / cm) Example 11.31 Example 20.67 Comparative Example 10.14 Comparative Example 20.38

[0247] In addition, from the measurement and evaluation results of the above experimental examples 2 and 3, the temperature-dependent activation energy and log(σ) of the electrolyte layer included in example 1 and comparative example 1 i ) is shown in comparison with Fig. 1, which shows the results of evaluating the electrolyte of Example 1. Referring to Fig. 1, it was confirmed that the electrolyte of Example 1 had an activation energy deviation (△Ea) of 0.02 eV or less depending on the temperature, and that there was almost no change in activation energy and ionic conductivity according to the absolute temperature change, and that it exhibited excellent ionic conductivity at all temperatures. In contrast, it was confirmed that the electrolyte of Comparative Example 1 showed a large change in activation energy and ionic conductivity according to the absolute temperature change, and that it exhibited a tendency for a rapid decrease in ionic conductivity and relatively poor ionic conductivity, especially in the low-temperature region.

[0248] In addition, based on the evaluation results of the experimental example 4 above, the thickness deformation rate of the positive electrode included in Example 1 when rolled using a roll was evaluated, and the results are shown in Fig. 2. Referring to Fig. 2, it was confirmed that the positive electrode film included in the battery of Example 1 exhibited excellent processability as the thickness of the positive electrode film decreased approximately inversely proportional to the gap between the rolls during the rolling process. In addition, based on Fig. 2 above, it became possible to manufacture a positive electrode having a constant porosity and elastic recovery rate, thereby minimizing errors caused by the positive electrode when evaluating the performance of a solid battery and identifying only the influence according to the properties of the solid electrolyte.

[0249] In addition, based on the evaluation results of Experimental Example 5, the results of the room temperature charge / discharge test of the solid battery of Example 1 are shown in Fig. 3, and the results of the room temperature and high temperature (60°C) charge / discharge test of the solid battery of Comparative Example 1 are shown in Fig. 4.

[0250] Referring to the above Figures 3 and 4, the solid battery of the example was manufactured by including a solid electrolyte having a high ionic conductivity of 1.3 mS / cm, thereby exhibiting excellent charge / discharge characteristics at room temperature, whereas the solid battery of the comparative example was practically unable to operate at room temperature due to the low ionic conductivity of the installed solid electrolyte, and it was confirmed that only high-temperature operation of 60°C or higher was possible, similar to a typical all-solid-state battery including a polymer solid electrolyte.

Claims

1. A solid-state battery comprising a positive electrode; a negative electrode; and an electrolyte layer interposed between the positive electrode and the negative electrode, The electrolyte layer comprises a polymer including a PEO (polyethylene oxide) copolymer having a cross-linking functional group at least partially forming a cross-linking bond; a ceramic compound; and a polar compound, wherein the polar compound is dispersed or bonded on the polymer, The above positive electrode is a solid battery including a positive electrode active material and a binder including a PEO copolymer having a cross-linking functional group.

2. A solid battery in the first paragraph, wherein the polar compound is dispersed between polymer chains forming the cross-linked bond, or is adsorbed or bonded to the surface or interior of the polymer chain.

3. A solid battery in the first paragraph, wherein at least some of the cross-linkable functional groups form cross-links with each other via a cross-linking agent.

4. In the first paragraph, the cross-linking functional group is bonded to the PEO copolymer 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), A solid battery 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. A solid-state battery according to claim 1, wherein at least one of the electrolyte layer or the positive electrode further comprises a lithium salt.

6. In the first paragraph, the PEO (polyethylene oxide) copolymer is a solid battery 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.

7. A solid battery according to claim 1, wherein the content of the polar compound is 0.1 wt% or more and less than 10 wt% based on the total weight of the electrolyte layer.

8. A solid battery according to claim 1, wherein the polar compound comprises at least one selected from the group consisting of carbonate compounds and sulfonyl compounds.

9. In the first paragraph, the ceramic compound is a solid-state battery including an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate.

10. In the first paragraph, the electrolyte layer is an all-solid-state battery having a temperature-dependent activation energy deviation (△Ea) defined by the following equation 1 of 0.03 eV or less. [Formula 1] ΔE a = E a LT - E a HT In the above equation 1, E a LT is the activation energy of the electrolyte layer at -40°C to 10°C, and E a HT is the activation energy of the electrolyte layer at 10℃ to 80℃, and ΔE a represents the temperature-dependent activation energy deviation defined as the difference between the two activation energies above.

11. In the first paragraph, the positive electrode is a solid battery that satisfies the thickness strain defined by the following equation 2 when rolled on both sides: [Formula 2] In the above equation 2, δ0 and d0 represent the initial roll gap and the initial thickness of the anode before rolling, and δ and d represent the roll gap and the thickness of the anode during rolling, and C and n are constants determined by regression analysis.

12. A solid-state battery according to claim 1, wherein the negative electrode comprises a lithium metal layer.

Images