solid-state batteries

Abstract

The present invention relates to a solid-state battery including a positive electrode, a negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode, wherein the electrolyte layer includes a polymer including a PEO (polyethylene oxide)-based copolymer having cross-linkable functional groups, at least a portion of which forms cross-links, a ceramic compound, and a polar compound, the polar compound being dispersed or bonded to the polymer, and the positive electrode includes a positive electrode active material and a binder including a PEO-based copolymer having cross-linkable functional groups.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority rights under Korean Patent Application No. 10-2023-0123075 dated September 15, 2023, and Korean Patent Application No. 10-2024-0123904 dated September 11, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] This invention relates to a solid-state battery including a solid electrolyte layer. [Background technology]

[0003] Lithium-ion batteries, which use liquid electrolytes, have a structure in which the negative and positive electrodes are separated by a separation membrane. If the separation membrane is damaged due to deformation or external impact, a short circuit may occur, which can lead to dangers such as overheating or explosion. Therefore, the development of solid electrolytes that can ensure safety in the field of lithium-ion secondary batteries is a very important issue.

[0004] Lithium-ion batteries (solid-state batteries) using solid electrolytes offer several advantages, including increased battery safety, prevention of electrolyte leakage, improved battery reliability, and ease of manufacturing thin batteries. Furthermore, the ability to use lithium metal as the negative electrode increases energy density, leading to expectations of applications in small secondary batteries as well as high-capacity secondary batteries for electric vehicles, making them a promising next-generation battery.

[0005] Among solid electrolytes, polymer solid electrolytes can use polymer materials that are ion-conducting, and can be used in the form of composite solid electrolytes in which inorganic materials are mixed with such polymer materials.

[0006] Such conventional hybrid (composite) solid electrolytes are produced by dispersing inorganic powders such as oxide-based ceramics in a polymer matrix. They have the advantages of having ignition and combustion stability compared to existing liquid electrolytes and having higher ionic conductivity compared to polymer solid electrolytes. However, there are difficulties in that basic prerequisites such as improving the dispersibility of oxide-based ceramic particles in the polymer matrix and optimizing the physical properties of the polymer matrix used must be satisfied. In particular, when using a highly crystalline polymer such as polyethylene oxide (PEO) as a matrix, there has been a problem that it is difficult to manufacture a composite solid electrolyte with improved ionic conductivity. That is, due to the high crystallinity of the PEO polymer, the chain mobility of the polymer is inhibited, and there are restrictions on the movement of lithium ions inside the polymer solid electrolyte. Therefore, there has been a limit to improving the ionic conductivity of the polymer solid electrolyte.

[0007] In particular, it has been difficult for conventional electrolytes to achieve ionic conductivity above a certain level at room temperature, which has restricted the development of solid-state batteries that can be driven at room temperature.

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, the present invention provides a solid-state battery including a solid electrolyte exhibiting excellent ionic conductivity.

Means for Solving the Problems

[0009] According to one embodiment of the invention, a solid-state battery including a positive electrode; a negative electrode; and an electrolyte layer interposed between the positive electrode and the negative electrode, wherein at least a part of the electrolyte layer includes a polymer including a PEO (polyethylene oxide)-based copolymer having a crosslinkable functional group that forms a crosslink; a ceramic compound; and a polar compound, and the polar compound is dispersed or bonded on the polymer. The positive electrode provides a solid-state battery including a positive electrode active material and a binder including a PEO-based copolymer having a crosslinkable functional group.

[0010] In such a solid-state battery, the polar compound may be dispersed between the polymer chains forming the cross-linkage, or adsorbed or bonded to the surface or inside of the polymer chains.

[0011] Further, at least a part of the cross-linkable functional groups can form a cross-linkage with each other via a cross-linking agent, and such cross-linkable functional groups are bonded to the PEO-based copolymer via an alkylene linker or an alkylene oxide linker having 0 to 10 carbon atoms (where the alkylene linker having 0 carbon atoms represents a single bond). 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.

[0012] In a more specific embodiment, the PEO (polyethylene oxide)-based copolymer may be a copolymer containing repeating units of the following Chemical Formulas 1 to 3:

Chemical formula

Chemical formula

Chemical formula

[0013] On the other hand, in the solid battery of the above embodiment, at least one of the electrolyte layer or the positive electrode may further contain a lithium salt.

[0014] Furthermore, in the solid-state battery, the content of the polar compound may be 0.1% by weight or more and less than 10% by weight, based on the total weight of the electrolyte layer, and the polar compound may include one or more selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0015] Furthermore, the ceramic compound may contain an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphorus oxide.

[0016] On the other hand, when the positive electrode is rolled using a roll on both sides, it can exhibit characteristics that satisfy the thickness deformation ratio defined by the following equation 2:

number

[0017] Furthermore, in the solid-state battery, the negative electrode may include a lithium metal layer. [Effects of the Invention]

[0018] A solid-state battery according to one embodiment of the invention includes a predetermined electrolyte layer manufactured by vapor deposition of a polar compound or the like. Such an electrolyte layer can exhibit improved ionic conductivity by maintaining the inherent structural properties of the polymer without deformation or destruction of the polymer chains, while improving the mobility of the polymer chains and uniformly distributing ceramic particles in the electrolyte.

[0019] Furthermore, by including a small amount of polar compound in the electrolyte, the ionic conductivity and mechanical properties of the polymer solid electrolyte can be improved.

[0020] By combining a composite electrolyte layer exhibiting such excellent ionic conductivity with a positive electrode to which the same type of binder as the composite electrolyte layer is applied, one embodiment of the solid battery can exhibit excellent charge and discharge characteristics at room temperature and high temperatures, and can also exhibit high ionic conductivity and mechanical properties. [Brief explanation of the drawing]

[0021] [Figure 1] This graph shows the results of evaluating the activation energy and log(σi) of the electrolyte layers contained in Example 1 and Comparative Example 1 at different absolute temperatures. [Figure 2] This graph shows the degree of thickness deformation when the positive electrode included in Example 1 is rolled using a roll. [Figure 3] This graph shows the charge and discharge test results of the solid-state battery of Example 1 at room temperature (25°C). [Figure 4]This graph shows the charge and discharge test results of the solid-state battery of Comparative Example 1 at room temperature (25°C) and high temperature (60°C). [Modes for carrying out the invention]

[0022] The following describes specific embodiments of the invention in more detail to facilitate understanding of the invention.

[0023] Terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0024] As used herein, the term "bonding" can mean a form in which a polar compound is "bonded" to a polymer chain, for example, a chain of a PEO-based polymer having crosslinking functional groups. Such "bonding" broadly refers to a form in which a polar solvent is vapor-deposited, for example, and the polar compound in a gaseous state is maintained fixed to the polymer chain. The term "bonding" is not limited to specific physical or chemical bonds, but is used to mean a state fixed by various bonds, including these physical and chemical bonds, or a state fixed by simple attachment such as adsorption, or a state in which it is contained within a three-dimensional network structure formed by the crosslinking of the polymer and is fixed adjacent to the polymer chain or crosslinking structure.

[0025] As used herein, the term "three-dimensional network structure" refers to a structure comprising a three-dimensional solid-shaped frame and an internal space formed by the frame, wherein the frame may include polymer chains comprising crosslinks formed by the crosslinkable functional groups, for example, crosslinks between crosslinkable functional groups and / or crosslinks between crosslinkable functional groups and crosslinking agents. The three-dimensional network structure may also be referred to as a crosslinked structure.

[0026] In this specification, the presence or inclusion of a polar compound (polar solvent) in an electrolyte in a "gaseous state" defines a state distinct from the case where the polar solvent or the electrolyte or polar solution containing it is injected in a liquid state. In other words, when the polar compound is deposited in a vapor state, it is present in a state distinct from the case where the polar solvent, etc., is injected in a liquid state immediately after the manufacture of the electrolyte or during the charging and discharging process of an all-solid-state battery containing it. However, depending on the storage or operating conditions of the electrolyte and / or battery, the vapor-deposited polar compound may be in a locally or temporarily liquefied state. Even in this case, the vapor-deposited polar compound exhibits a higher mobility than the liquid-injected polar solvent, etc., and thus is considered to be present or contained in a "gaseous state".

[0027] In this specification, the term "solid-state battery" may be interpreted to include not only so-called all-solid-state batteries, which contain no liquid at all in the entire battery structure including the electrolyte (layer), but also cases where, due to storage or operating conditions of the electrolyte and / or the battery, for example, a polar compound vapor-deposited onto the electrolyte becomes locally or temporarily liquefied, resulting in the presence of a small amount of liquid.

[0028] On the other hand, conventionally, 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, such electrolytes had problems such as the non-uniform distribution of oxide-based ceramic particles in the polymer matrix, or a decrease in ionic conductivity when a highly crystalline polymer such as polyethylene oxide was used as the polymer.

[0029] Therefore, in order to improve the ionic conductivity of the solid electrolyte and enhance the dispersibility of the ceramic compound, the solid electrolyte was immersed in or supported in an electrolyte or a liquid solvent, or an electrolyte or polar solvent was directly injected into the solid electrolyte in a liquid state. When a considerable 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 provided by the application of the solid electrolyte may be hindered. Furthermore, the improvement in ionic conductivity by adding the electrolyte or polar solvent was not sufficient, and the injection of a considerable amount of polar solvent was necessary.

[0030] Furthermore, when a liquid electrolyte or polar solvent is directly added or injected into a solid electrolyte in a liquid state, there are problems such as the collapse of the solid electrolyte structure due to unexpected side reactions between the polymer and the liquid phase, such as damage to the polymer chain or breakage of bonds within the polymer, which reduces the ionic conductivity. Moreover, at low temperatures, where ion mobility in the liquid electrolyte decreases, this ionic conductivity becomes even lower, which is a significant disadvantage.

[0031] Furthermore, when a polar solvent or liquid electrolyte is directly injected into a solid electrolyte, the rapid diffusion of liquid phase molecules into the solid electrolyte can cause rapid relaxation of polymer chains, promoting gelation at the surface and potentially leading to a decrease in mechanical properties. In addition, problems such as leakage of the liquid electrolyte or polar solvent may occur, reducing the safety of the battery.

[0032] Therefore, the present inventors applied a vapor deposition method to an electrolyte containing a polymer and a ceramic compound, which are crosslinked polymers of PEO (polyethylene oxide) copolymers modified with crosslinkable functional groups, to which a polar compound derived from a polar solvent was vapor-deposited. The electrolyte thus produced contains a polymer containing a PEO polymer containing crosslinkable functional groups; a ceramic compound; and a polar compound, wherein at least a portion of the crosslinkable functional groups form crosslinks with each other, forming a three-dimensional network structure in the polymer, and the polar compound can be contained within the three-dimensional network structure or exhibit a structure bonded to the polymer chain.

[0033] Such electrolytes have been confirmed to exhibit improved ionic conductivity despite containing polar compounds derived from trace amounts of polar solvents. In such electrolytes, the polar compounds can exhibit different states from those of polar solvents injected in large quantities due to vapor deposition and their trace content. For example, at least a portion of the polar compounds can exist in a gaseous state in the electrolyte and can be locally or temporarily converted to a liquid or gas-liquid coexistence state during battery operation. Furthermore, the polar compounds can be uniformly dispersed within the three-dimensional network structure defined by the crosslinking bonds, or can be bound to or attached to polymer chains between the three-dimensional networks.

[0034] It is predicted that these different states of polar compounds will affect the physical properties of PEO-based polymers, such as crystallinity, thereby increasing the chain mobility of the polymer chains and improving the lithium ion conductivity contained in the electrolyte. Furthermore, the electrolyte can exhibit even better ionic conductivity due to the uniform dispersion of ceramic compounds within the three-dimensional network structure.

[0035] The polar compound may be present in an amount of 0.1% by weight or more and less than 10% by weight, based on the total weight of the electrolyte. For example, the content of the polar compound may be 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, or 3% by weight or more, or 4% by weight or less, 5% by weight or less, 6% by weight or less, 7% by weight or less, 8% by weight or less, 9% by weight or less, or less than 10% by weight. If the content of the polar compound is less than 0.1% by weight, it is difficult to induce a change in the chain conformation of the polymer chains, and despite vapor deposition of the polar compound, the ionic conductivity of the electrolyte does not improve sufficiently. Conversely, if the content of the polar compound is 10% by weight or more, it exhibits the same state as a polar solvent injected in liquid form in the electrolyte, making it difficult to achieve the effect of vapor deposition. As a result, there is a large content of polar solvent or electrolyte that is substantially always present in a liquid state in the electrolyte, which can lead to the properties of a semi-solid battery, and the mechanical strength of the electrolyte may decrease due to the gelation of the polymer, and the ionic conductivity of the electrolyte may also become insufficient.

[0036] The amount of polar compounds contained in the electrolyte can be calculated by measuring the amount of polar compounds evaporated while the electrolyte is heated. Specifically, considering the boiling point and vapor pressure of the polar compounds at different temperatures, the amount can be calculated by heating the electrolyte at a temperature where the polar compounds begin to evaporate, for example, 40°C or above, or 50°C or above, while increasing the temperature to the boiling point or 10°C above the boiling point, collecting the polar compounds evaporated within that temperature range as a liquid phase, and measuring the weight of this liquid phase. The calculation can be stopped when the measured amount reaches a saturation point (for example, when the measured amount does not increase further) as the heating time under the increasing temperature increases, and this is considered to be the total amount of polar compounds contained in the electrolyte.

[0037] Furthermore, the content of the polar compound in the electrolyte can be adjusted in the vapor deposition stage described later by the amount of polar compound used and / or the progress conditions such as the vapor deposition time and temperature, which will be evident from the examples described later.

[0038] On the other hand, the electrolyte can exhibit superior ionic conductivity due to the ceramic compound uniformly dispersed within the three-dimensional network structure.

[0039] Therefore, the electrolyte, while substantially free of liquid polar solvents or electrolytes, exhibits improved ionic conductivity and can contribute to the development of solid-state batteries with excellent physical properties.

[0040] Therefore, one embodiment of the invention, a solid-state battery, contains the aforementioned electrolyte, as well as a positive electrode that is suitably combined therewith, thereby exhibiting excellent ionic conductivity and various properties.

[0041] In a specific example, the polar compound may be dispersed between polymer chains that have formed a three-dimensional network structure by crosslinking in a vapor-deposited gaseous state, or it may be adsorbed or bound to the surface or interior of the polymer chains.

[0042] Such electrolytes contain polar compounds that are incorporated or bonded to a three-dimensional network structure in small amounts by vapor deposition, as described later. Such polar compounds have a different state from polar solvents that are injected into the electrolyte in large quantities in a liquid state. The state of such polar compounds can be confirmed, for example, by observing the electrolyte layer containing the polar compounds with the naked eye or an electron microscope after separating it from an all-solid-state battery or the like at a temperature lower than the boiling point of the polar compounds. If no liquid components are observed on the surface of the electrolyte layer under such observation, it is considered that the polar compounds have a state similar to that of an electrolyte that has been vapor-deposited.

[0043] In contrast, when a liquid polar solvent or electrolyte is injected into the electrolyte, liquid components or components exhibiting wettability can be observed on the surface of the electrolyte layer. Furthermore, as can be confirmed in the examples described later, electrolytes on which the polar compound has been vapor-deposited exhibit improved ionic conductivity compared to cases where a liquid polar solvent or electrolyte is injected, even with a lower content of the polar compound. By comparing such ionic conductivity, the presence of the polar compound vapor-deposited into the electrolyte, whether in a gaseous state or elsewhere, can be confirmed.

[0044] On the other hand, in the electrolyte, the crosslinkable functional group may be directly bonded to the main chain of the PEO copolymer, but it can also be bonded via an alkylene or alkylene oxide linker. For this reason, the crosslinkable functional group can be bonded via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms shows a single bond), and may be one or more selected from the group consisting of hydroxyl group, carboxyl group, isocyanate group, nitro group, cyano group, amine group, amide group, epoxy group, and allyl group.

[0045] In one embodiment of the invention, the crosslinking functional groups may be two or more types. The crosslinking functional groups may be the same or different from each other. If the crosslinking functional groups are different, multiple repeating units containing each of these functional groups may be included. Furthermore, if multiple types of crosslinking functional groups are included, it may become easier to control the mobility and ionic conductivity of the polymer chain.

[0046] The aforementioned crosslinkable functional groups refer to functional groups that can form crosslinks between other crosslinkable functional groups and / or form crosslinks with each other via a crosslinking agent, and can be attached to polymer chains in the form of side chains.

[0047] In a more specific embodiment, the PEO copolymer containing the crosslinkable functional group may be a copolymer containing repeating units of the following chemical formulas 1 to 3: [ka] [ka] [ka] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3 is represented, where k is 0 to 20, and R3 represents an alkyl group with 1 to 5 carbon atoms. R2 represents a substituent in which one or more crosslinking functional groups selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, nitro groups, cyano groups, amine groups, amide groups, epoxy groups, and allyl groups are bonded to the polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (where the alkylene linker having 0 carbon atoms shows a single bond). l, m, and n are the number of repetitions in the repeating unit, where l and n are independent integers between 1 and 100,000, or 50 and 80,000, or 100 and 50,000, respectively, and m is an integer between 0 and 100,000, or 50 and 80,000, or 100 and 50,000.

[0048] For example, the crosslinking functional group of R2 can form a matrix polymer with a three-dimensional network structure formed by the crosslinking. The formation of this three-dimensional network structure by crosslinking can improve the mechanical properties of the electrolyte, and an electrolyte with improved ionic conductivity can be provided by containing or bonding polar compounds within such a three-dimensional network structure.

[0049] Furthermore, it is obvious that the PEO copolymer may contain two or more repeating units of chemical formula 3 in which R2 is a different crosslinking functional group, and may also contain one or more repeating units of chemical formula 2.

[0050] If l, m, and n are each excessively small, forming a polymer becomes difficult due to the low molecular weight. If l, m, and n are each excessively large, the increased viscosity reduces solubility during the production of polymer solutions, potentially making molding for electrolyte production difficult. In particular, if the number of repeating units containing crosslinking functional groups among l, m, and n is excessively large, the degree of crosslinking may increase excessively, reducing the mobility of the polymer chain and decreasing ionic conductivity.

[0051] On the other hand, in this specification, "hydroxyl group" refers to the -OH group.

[0052] In this specification, "carboxyl group" refers to a -COOH group.

[0053] In this specification, "isocyanate group" refers to a -N=C=O group.

[0054] In this specification, "nitro group" refers to the -NO2 group.

[0055] In this specification, "cyano group" refers to a -CN group.

[0056] In this specification, "amide group" refers to -C(=O)NR'R'', where R' and R'' may each independently be hydrogen or a C1-C5 alkyl group, or R' and R'' may form a heterocycle having a C4-C8 atom in the ring structure together with the N atom to which they are attached.

[0057] In this specification, "amine group" can be selected from the group consisting of monoalkylamine group; monoarylamine group; monoheteroarylamine group; dialkylamine group; diarylamine group; diheteroarylamine group; alkylarylamine group; alkylheteroarylamine group; and arylheteroarylamine group, and the number of carbon atoms is not particularly limited, but is preferably 1 to 30. Specific examples of the amine group include, but are not limited to, methylamine group, dimethylamine group, ethylamine group, diethylamine group, phenylamine group, naphthylamine group, biphenylamine group, dibiphenylamine group, anthracenylamine group, 9-methyl-anthracenylamine group, diphenylamine group, phenylnaphthylamine group, ditolylamine group, phenyltolylamine group, triphenylamine group, biphenylnaphthylamine group, phenylbiphenylamine group, biphenylfluorenylamine group, phenyltriphenylenylamine group, and biphenyltriphenylenylamine group. Furthermore, "amino group" refers to -NH2.

[0058] In this specification, "allyl group" refers to the -CH2-CH=CH2 group.

[0059] The weight-average molecular weight (Mw) of the cross-linked PEO copolymers described above may be between 100,000 g / mol and 4,000,000 g / mol, and more specifically, may be 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, or 3,000,000 g / mol or less, or 2,000,000 g / mol or less. If the weight-average molecular weight (Mw) of the copolymer is excessively small, the mechanical properties of the electrolyte produced may not be satisfied. If the weight-average molecular weight (Mw) of the copolymer is excessively large, the solubility may decrease during the production of the polymer solution due to increased viscosity, which may make molding for electrolyte production difficult. In addition, the ionic conductivity of the electrolyte may decrease due to increased crystallinity and decreased chain mobility within the electrolyte.

[0060] Furthermore, if the number of repeating units of chemical formula 3 containing crosslinking functional groups is excessively large, the degree of crosslinking may increase excessively, reducing the mobility of the polymer chain and decreasing the ionic conductivity of the electrolyte.

[0061] Furthermore, the copolymer may be a random copolymer or a block copolymer.

[0062] On the other hand, in one specific embodiment of the invention, the polar compound may be contained in or bonded to the surface or interior of the polymer chain by vapor deposition, for example, in a substantially gaseous state (including a local, temporary liquid state). Specifically, the polar compound can be diffused or dispersed between polymer chains that form a three-dimensional network structure by crosslinking of the crosslinkable PEO-based polymer, or it can be adsorbed or bonded to the surface or interior of the polymer chain.

[0063] The polar compound is a gaseous molecule of a polar solvent used in the vapor deposition process. After the gaseous molecule of the polar solvent is adsorbed onto the polymer during vapor deposition, it may diffuse into the interior of the polymer chains and be bound to the polymer chains, or it may be included in a form that is dispersed or diffused in the internal space between the polymer chains. By including the polar compound in a form that is bound to the polymer chains or dispersed in the internal space between the polymer chains, the ionic conductivity of the final manufactured electrolyte can be improved.

[0064] Specifically, polar compounds that are bound to the polymer chains or contained between the polymer chains act as plasticizers, causing the polymer to plasticize. The plasticized polymer has an increased amount of amorphous regions inside, which improves the mobility of the polymer chains. This improved mobility of the polymer chains increases the ion hopping effect inside the polymer, thereby improving the ionic conductivity of the electrolyte.

[0065] Furthermore, 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, lithium ions can be transferred more quickly and easily within the polymer on which the polar compound is adsorbed. In other words, as the polar compound flows into the polymer, the cation solvation effect of lithium ions increases, improving ion mobility and thereby improving the ionic conductivity of the electrolyte.

[0066] Furthermore, the polar compound may include one or more compounds selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0067] Specifically, the polar compound may include one or more selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane, or a combination thereof.

[0068] As described above, the content of the polar compound may range from 0.1% by weight or more to less than 10% by weight, based on the total weight of the electrolyte. For example, the content of the polar compound may be 0.1% by weight or more, 1% by weight or more, 2% by weight or more, or 4% by weight or less, 5% by weight or less, 6% by weight or less, 7% by weight or less, 8% by weight or less, 9% by weight or less, or less than 10% by weight.

[0069] In one embodiment of the invention, the electrolyte may include crosslinking between crosslinking functional groups. The electrolyte may further include a crosslinking agent and further include crosslinking between the crosslinking agent and the crosslinking functional groups. For example, at least some of the crosslinking functional groups may form crosslinking bonds with each other via the crosslinking agent to form the three-dimensional network structure described above.

[0070] The aforementioned crosslinking bond may be a urethane bond, an ester bond, a hydrogen bond, or a bond formed by a radical polymerization reaction involving vinyl groups at the terminal ends of an allyl group (-CH2-CH=CH2), but is not limited to these examples.

[0071] Furthermore, when a crosslinking agent is added in the electrolyte manufacturing process, a crosslink bond may be formed between the crosslinking agent and the crosslinkable functional group, and the crosslink bond may be formed by hydrogen bonding, Lewis acid-base interaction, ionic bonding, coordination bonding, or radical polymerization.

[0072] The crosslinking agent is not particularly limited as long as it is a polyfunctional crosslinking agent capable of forming crosslink bonds with the crosslinking functional group. For example, the crosslinking agent is trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol dimethyl acrylate (hereinafter referred to as "EGDMA"), 1,3-diisopropenylbenzene (DIP), 1,4-diacryloyl piperazine, 2-(diethylamino)ethyl methacrylate, 2,6-bisacryloylamidopyridine, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acrylamide)benzoic acid (3,5-bis(acryloylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methylacryloxypropyltrimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene, ethylene glycol maleic rosinate acrylate N,O-bisacryloylphenylalaninol, N,O-bismethacryloylethanolamineOne or more polyfunctional crosslinking agents selected from the group consisting of O-bismethacryloyl ethanolamine, pentaerythritol triacrylate, phenyltrimethoxysilane, tetramethoxysilane, tetramethylene, tetraethoxysilane, and triallyl isocyanurate, for example, a polyvalent compound with two or more functions.

[0073] Furthermore, the crosslinking agent may be present in an amount of 1 to 30 parts by weight per 100 parts by weight of the PEO copolymer containing the crosslinking functional group contained in the polymer mixture. If the amount of the crosslinking agent is less than 1 part by weight, sufficient crosslinking with the crosslinking functional group may not occur, and if it exceeds 30 parts by weight, excessive crosslinking may occur, which may actually decrease the mobility of the polymer chain and thus lower the ionic conductivity.

[0074] In one embodiment of the invention, the electrolyte may further contain a lithium salt. The lithium salt is contained in a dissociated ionic state in the internal space between the polymer chains, thereby improving the ionic conductivity of the electrolyte. At least some of the cations and / or anions dissociated from the lithium salt remain bound to the polymer chains and can exhibit mobility during charging and discharging of the battery.

[0075] The lithium salts mentioned above are (CF3SO2)2NLi (Lithium bis(trifluoromethanesulfonyyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10It may contain one or more selected from the group consisting of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0076] Furthermore, the lithium salt may be present in 25 to 45 parts by weight per 100 parts by weight of the polymer mixture, specifically, 25 parts by weight or more, 30 parts by weight or more, or 35 parts by weight or more, or 40 parts by weight or less, or 45 parts by weight or less. If the lithium salt content is less than 25 parts by weight, the ionic conductivity of the electrolyte may decrease, and if it exceeds 45 parts by weight, the mechanical strength may decrease.

[0077] The electrolyte described above may include a ceramic compound. The ceramic compound has lithium ion transfer capability to improve lithium ion conductivity, and preferably contains lithium atoms but can have the function of moving lithium ions without storing lithium, thereby improving the ionic conductivity of the electrolyte.

[0078] Furthermore, the ceramic compound may be included in a state where it is uniformly dispersed between the crosslinked polymer chains, for example, within the three-dimensional network structure. The ceramic compound can be added together in the crosslinking process and dispersed uniformly without clumping between the polymer chains formed by the crosslinking. Such a ceramic compound may be advantageous in improving the mechanical strength and ionic conductivity of the electrolyte due to its uniform dispersion form.

[0079] Also, the ceramic compound may be in a particulate form. Due to the morphological feature of particles, it may be contained in a more uniformly dispersed state inside the electrolyte. The particles of the ceramic compound may be spherical, and their diameter may be 100 nm to 1000 nm. If the diameter is less than 100 nm, the effect of amorphization due to the decrease in the crystallinity of the polymer is slight. If it exceeds 1000 nm, the dispersibility may decrease due to an increase in aggregation between particles, and it may be difficult to disperse uniformly.

[0080] The ceramic compound may be an oxide-based or phosphate-based compound. For example, it may become an oxide-based solid electrolyte in the form of a lithium metal oxide or a lithium metal phosphate. More specifically, the ceramic compound is a garnet (Garnet)-type lithium-lanthanum-zirconium oxide-based (LLZO, Li7La3Zr2O 12 ) compound, a perovskite (perovskite)-type lithium-lanthanum-titanium oxide-based (LLTO, Li3xLa 2 / 3-x TiO3) compound, a phosphate (phosphate)-based NASICON (NASICON)-type lithium-aluminum-titanium phosphate-based (LATP, Li 1+x Al x Ti 2-x (PO4)3) compound, a lithium-aluminum-germanium phosphate-based (LAGP, Li 1.5 Al 0.5 Ge 1.5One or more can be selected from the group consisting of (PO4)3) compounds, lithium-silicon-titanium phosphate (LSTP, LiSiO2TiO2(PO4)3) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds. More preferably, one or more oxide-based solid electrolytes 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.

[0081] The aforementioned oxide-based or phosphate-based oxide-based solid electrolytes generally have a maximum capacity of 10 at room temperature. -4 ~10 -3 It has an ionic conductivity value of S / cm, is stable in the high-voltage range, and has the advantages of being stable in air, easy to synthesize, and easy to handle.

[0082] Furthermore, the ceramic compound does not easily burn or ignite even under high-temperature conditions of 400°C or higher, thus exhibiting high high-temperature stability. Therefore, when the electrolyte contains the ceramic compound, it is possible to improve not only the mechanical strength of the electrolyte but also its high-temperature stability and ionic conductivity.

[0083] The ceramic compound may be present 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, per 100 parts by weight of the polymer mixture.

[0084] If the ceramic compound is present in an excessively small amount, the reduction in polymer crystallinity and amorphous effect due to the ceramic compound will decrease, resulting in a less significant increase in the ionic conductivity of the electrolyte, and the overall mechanical properties of the electrolyte may also be insufficient.

[0085] If the ceramic compound is present in an excessively large amount, the ceramic compound will not be uniformly dispersed within the polymer, and the ceramic compound particles will aggregate and clump together, resulting in the production of an electrolyte with reduced ionic conductivity.

[0086] On the other hand, the electrolytes mentioned above can exhibit excellent ionic conductivity. For example, such electrolytes can show excellent ionic conductivity of 0.6 mS / cm or higher, or 0.9 mS / cm or higher, or 0.95 mS / cm or higher, or 0.95 mS / cm to 1.50 mS / cm, when measured at room temperature of approximately 25°C.

[0087] Such ionic conductivity can be calculated from the resistance (Ω) of the electrolyte measured with an electrochemical impedance spectrometer at a constant temperature, such as room temperature, using the following equation 4:

number

[0088] On the other hand, the electrolytes mentioned above can exhibit the characteristic that the activation energy deviation (ΔEa) at different temperatures, as defined by Equation 1 below, is 0.03 eV or less, or 0.005 to 0.025 eV:

number

[0089] At this time, the activation energy deviation can be calculated from the ionic conductivity of the electrolyte measured at different absolute temperatures. More specifically, the ionic conductivity (σ) at different temperatures i Based on the measurement results of ), log(σ i The relationship between ) and 1000 / T (where T is the absolute temperature at which the ionic conductivity was measured) can be fitted using the Arrhenius equation in Equation 3 below to derive the activation energy Ea corresponding to the slope, and then E in Equation 1 above a LT , E a HT and ΔE a Each of these can be calculated.

number

[0090] Such low activation energy deviations confirm that the aforementioned electrolytes exhibit excellent ionic conductivity and electrochemical properties without significant deviations, even with changes in temperature.

[0091] The above-described method for producing the electrolyte may include the steps of: mixing a PEO-based copolymer containing the crosslinkable functional group and a ceramic compound, then proceeding with a crosslinking reaction with respect to the PEO-based copolymer contained in the mixture; and vapor-depositing a polar solvent onto the mixture containing the crosslinked polymer.

[0092] The description of the PEO copolymer containing the aforementioned crosslinking functional group is as described above.

[0093] In this manufacturing method, a PEO-based copolymer containing crosslinking functional groups and a ceramic compound are first mixed, and then a crosslinking reaction is carried out on the PEO-based copolymer contained in the mixture to produce a polymer that forms the three-dimensional network structure described above.

[0094] The crosslinking reaction can be carried out in the presence of one or more additional substances selected from the group consisting of crosslinking agents and initiators.

[0095] Furthermore, lithium salts may be added together during the mixing and / or crosslinking reaction stages to form the electrolyte.

[0096] Furthermore, the ceramic compound used can be the same as the one used in the electrolyte described earlier, and the content can also be the same.

[0097] The crosslinking reaction may occur during the drying process after applying a solution containing the crosslinked PEO copolymer and ceramic compound, etc., onto a substrate to form a coating film.

[0098] Specifically, the mixed solution can be produced by mixing the crosslinked PEO copolymer and the ceramic compound in a solvent, and additionally, by mixing a crosslinking agent, initiator, and / or lithium salt together. Alternatively, a mixed solution or suspension may be produced by first producing a solution containing the crosslinked PEO copolymer, crosslinking agent, initiator, and / or lithium salt, and then adding the ceramic compound.

[0099] The solvent is not particularly limited as long as it can be mixed with the crosslinked PEO copolymer, 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), methylpyrrolidone (NMP), or dimethylformamide (DMF). Such a solvent is a reaction medium for crosslinking, and is distinct from polar solvents contained in liquid electrolytes, etc., and is completely removed by drying or other means after crosslinking.

[0100] The concentration of the mixed solution can be appropriately adjusted, taking into consideration the degree to which the molding process for electrolyte production can proceed smoothly. Specifically, the concentration of the polymer solution may mean the concentration of polymer (w / w%) in the polymer solution. The concentration of the polymer may also mean the concentration of the cross-linked PEO copolymer. For example, the concentration of the polymer solution may be 5% to 20% by weight, and specifically, it may be 5% or more by weight, 7% or more by weight, or 9% or more by weight, or 13% or less by weight, 17% or less by weight, or 20% or less by weight. If the concentration of the polymer solution is less than 5% by weight, the concentration may be too dilute, reducing the mechanical strength of the electrolyte or causing it to run off the substrate when applied. If it exceeds 20% by weight, it may be difficult to dissolve the lithium salt in the polymer solution at the desired concentration, the viscosity may be high, reducing solubility, or it may be difficult to apply it in a uniform thin film form.

[0101] The substrate is not particularly limited as long as it serves as a support for the coating film. For example, the substrate may be SUS (Steel Use Stainless), polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0102] Furthermore, the coating method is not particularly limited as long as it is a method that can form a coating film by applying the polymer solution onto 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.

[0103] The coating film formed on the substrate by this coating method can be formed into a polymer film with the residual solvent completely removed by a drying process. To prevent shrinkage of the polymer due to rapid evaporation of the solvent, the drying process can be divided into a primary drying process and a secondary drying process. The primary drying process can remove part of the solvent by drying at room temperature, and the secondary drying process can completely remove the solvent by high-temperature vacuum drying. The high-temperature drying can be carried out at a temperature of 80°C to 130°C. If the high-temperature drying temperature is below 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.

[0104] Furthermore, the crosslinking agent may form a bond with the crosslinking functional group. The type of crosslinking agent, the content of the crosslinking agent, and the type of bond with the crosslinking functional group are described above.

[0105] Furthermore, the initiator can induce a radical polymerization reaction between the crosslinking functional groups so that crosslinks are formed between them. The functional group that enables the radical polymerization reaction may be a functional group that contains vinyl at its terminal end, or it may be, for example, an allyl group.

[0106] The initiator is not particularly limited as long as it is an initiator capable of inducing a radical polymerization reaction between the crosslinking functional groups. For example, the initiator may include one or more selected from the group consisting of benzoyl peroxide, azobisisobutyronitrile, lauroyl peroxide, cumene hydroperoxide, diisopropylphenyl-hydroperoxide, tert-butyl hydroperoxide, p-methyl hydroperoxide, and 2,2'-azobis(2-methylpropionitrile).

[0107] The initiator can be used in amounts of 0.5 to 2 parts by weight per 100 parts by weight of the crosslinked PEO polymer containing the crosslinkable functional group. When used within this range, it is possible to induce radical polymerization reactions between the crosslinkable functional groups and efficiently form crosslinks.

[0108] Furthermore, the explanation regarding the content and type of lithium salt is as described above.

[0109] In the vapor deposition step, the crosslinked result can be exposed to vaporized polar compound (polar solvent) and vapor-deposited.

[0110] Specifically, the vapor deposition can be carried out by heating the polar solvent to a temperature above room temperature to obtain a vapor of the polar compound, which is then brought into contact with the crosslinked result and allowed to penetrate into the interior. Through such vapor deposition, the polar compound may be uniformly diffused onto the surface and / or interior of the polymer, for example, in a gaseous state, and the polar compound gas molecules may be bonded to the polymer chain, or uniformly dispersed or diffused within the internal space of the polymer chain.

[0111] When a polar solvent is left at room temperature during vapor deposition, a small amount of polar solvent with a low boiling point can be gradually vaporized at room temperature and allowed to penetrate into the polymer, effectively inducing a change in the conformation of the cross-linked polymer chains within the polymer.

[0112] Furthermore, when heating the polar solvent during vapor deposition, the vapor deposition rate can be improved. In this case, the heating temperature is not particularly limited as long as it is a temperature at which the polar solvent can undergo a phase change into vapor, and may be, for example, 30°C to 80°C. While typical PEO melts at 60°C, PEO copolymers modified with the crosslinking functional group have improved heat resistance and can withstand temperatures up to 80°C when forming a crosslinked structure, thus enabling an even faster vapor deposition rate. The heating method is not limited as long as it can supply the energy to generate vapor. For example, direct heating methods using a burner or furnace, or indirect heating methods using a heater or steam tube can be used, but the method is not limited to these examples.

[0113] When heating, if the temperature is excessively high, the polar solvent may boil above its boiling point, structural changes in the solvent may occur, or deformation of the polymer may be induced. This has the disadvantage of making it difficult to control the evaporation rate of the polar solvent during vapor deposition. Therefore, in order to perform vapor deposition with a small amount of polar solvent, it is preferable to perform vapor deposition at a heating temperature within the appropriate range as defined above.

[0114] On the other hand, the content of polar compounds in the final electrolyte can be adjusted by controlling the temperature, heating rate, amount of polar solvent (polar compound) used for evaporation during vapor deposition, and the time and rate of vapor deposition, as is clearly demonstrated by the examples below.

[0115] solid state battery 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 and negative electrodes, wherein the solid electrolyte layer may include the electrolyte described above.

[0116] In such a solid-state battery, the positive electrode active material layer may include a positive electrode active material and a binder containing a PEO-based copolymer having crosslinking functional groups. In a more specific example, the PEO-based copolymer having crosslinking functional groups may be the same as or identical to the one contained in the electrolyte layer described above. Furthermore, the PEO-based copolymer, like the one contained in the electrolyte layer, may have at least some of its crosslinking functional groups capable of forming crosslinks.

[0117] By including such a crosslinked PEO copolymer as the binder in the positive electrode active material layer, the interfacial and bonding properties between the positive electrode active material layer and the solid electrolyte layer can be improved. Therefore, the solid-state battery of the above embodiment can exhibit superior ionic conductivity and mechanical properties.

[0118] Furthermore, depending on the type of binder used for the positive electrode active material, it becomes easier to control the thickness of the positive electrode by adjusting the process conditions during the rolling process, resulting in superior processability.

[0119] More specifically, the positive electrode may be formed, for example, by coating a positive electrode active material layer onto a positive electrode current collector and then rolling it. In this case, when the positive electrode is rolled on both sides using a roll, it can satisfy the thickness deformation ratio defined by the following formula 2.

number

[0120] For reference, C and n can be used as criteria for classifying the properties of electrode manufacturing materials based on their material-specific physical properties. Based on the above formula, it becomes possible to manufacture a positive electrode with a constant porosity and elastic recovery rate, which has the advantage of minimizing errors caused by the positive electrode during performance evaluation of solid-state batteries and allowing only the influence of the solid electrolyte's physical properties to be understood.

[0121] The characteristics of Equation 2 indicate that, when the rolling process is carried out using a roll-to-roll method, the thickness ratio of the positive electrode is approximately inversely proportional to the ratio of the gap between the rolling rolls. This makes it easier to form a positive electrode and positive electrode active material layer of the desired thickness by the rolling process, resulting in excellent processability.

[0122] On the other hand, the positive electrode active material layer may further contain a conductive material in addition to the positive electrode active material and binder.

[0123] Furthermore, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly intercepting and releasing lithium ions, for example, lithium cobalt oxide, lithium nickel oxide, Li[NixCoyMnzMv]O2 (wherein M is one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, x+y+z+v=1), Li(LiaMb-a-b'M'b')O2 2-c A c Layered compounds such as (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, and 0≦c≦0.2; M comprises Mn and one or more elements selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more elements selected from the group consisting of Al, Mg, and B, and A is one or more elements selected from the group consisting of P, F, S, and N) or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-yLithium 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 as MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-y M y Lithium manganese composite oxides represented as O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and y = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc., are examples, but are not limited to these.

[0124] Furthermore, the positive electrode active material may be present in an amount of 40 to 90% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40% or more by weight, 50% or more by weight, 90% or less by weight, or 80% or less by weight. If the content of the positive electrode active material is less than 40% by weight, the connectivity and electrical properties between the positive electrode active materials may be insufficient, and if it exceeds 90% by weight, the mass transfer resistance may increase.

[0125] Furthermore, the binder is a component that assists in the bonding of the positive electrode active material to conductive materials and to the current collector, and may include the cross-linking PEO copolymer described above. However, in addition to such copolymers, it may further include general binders.

[0126] Examples of such additional binders are not particularly limited and include, for example, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, It may contain one or more selected from the group consisting of latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, 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.

[0127] However, in a more appropriate example, the binder may mainly consist of a PEO copolymer having the same or identical crosslinking functional groups as those contained in the electrolyte. In this way, by including the same type of binder as the solid electrolyte layer in the positive electrode active material layer, the solid-state battery can exhibit excellent mechanical properties along with excellent charge-discharge characteristics and ionic conductivity. In a more specific example, the PEO copolymer having the crosslinking functional groups may be included in the total binder in a ratio of 60% or more by weight, or 80% or more by weight, or 90-100% by weight.

[0128] Furthermore, the binder may be present in an amount of 1% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1% or more by weight, 3% or more by weight, 15% or less by weight, or 30% or less by weight. If the binder content is less than 1% by weight, the adhesive strength between the positive electrode active material and the positive electrode current collector may decrease. If it exceeds 30% by weight, the adhesive strength will improve, but the amount of positive electrode active material will decrease accordingly, potentially reducing the battery capacity.

[0129] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the solid battery and has excellent electrical conductivity without inducing chemical changes in the battery. Typically, graphite or conductive carbon can be used, for example, graphite such as natural graphite or 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 whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which can be used individually or in mixtures of two or more, but are not necessarily limited to these.

[0130] The conductive material may typically be present in an amount of 0.5% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5% or more by weight, 1% or more by weight, 20% or less by weight, or 30% or less by weight. If the content of the conductive material is excessively low, such as less than 0.5% by weight, it may be difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the battery may deteriorate. If it is excessively high, such as more than 30% by weight, the amount of positive electrode active material may be relatively reduced, leading to a decrease in capacity and energy density. The method for incorporating the conductive material into the positive electrode is not significantly limited, and conventional methods known in the art, such as coating the positive electrode active material, can be used.

[0131] Furthermore, the positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between the external conductor and the positive electrode active material layer.

[0132] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without inducing chemical changes in the solid battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., and aluminum-cadmium alloys can be used as the positive electrode current collector.

[0133] The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. This allows the positive electrode current collector to take on a variety of forms, such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0134] Such positive electrodes can be manufactured by conventional methods. Specifically, a composition for forming a positive electrode active material layer, prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent, is applied to a positive electrode current collector and dried, and then selectively compressed and molded onto the current collector to improve electrode density. In this case, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that evaporates easily. Specifically, examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP, N-Methyl-2-Pyrrolidone).

[0135] On the other hand, the negative electrode contained in the solid battery may include 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.

[0136] The negative electrode active material is lithium (Li + This may include materials that can be reversibly intercalated or deintercalated, materials that can react with lithium ions to reversibly form lithium-containing compounds, lithium metal, or lithium alloy. In particular, by including a lithium metal layer in the negative electrode, the solid-state battery can exhibit superior energy density and conductivity.

[0137] The aforementioned lithium ion (Li + The material from which the lithium ions (Li) can be reversibly inserted or removed may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + A substance capable of reversibly forming a lithium-containing compound by reacting with ) may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) with 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).

[0138] Preferably, the negative electrode active material may be lithium metal, and more specifically, it may be in the form of a lithium metal thin film or lithium metal powder.

[0139] The negative electrode active material may be present in an amount of 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the negative electrode active material is less than 40% by weight, the electrical properties may not be sufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0140] Furthermore, the binder is as described above in the positive electrode active material layer.

[0141] Furthermore, the conductive material is as described above in the positive electrode active material layer.

[0142] Furthermore, the negative electrode current collector is not particularly limited as long as it is conductive without inducing a chemical change in the battery. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. In addition, the negative electrode current collector can be made of various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics with fine irregularities formed on their surface, similar to the positive electrode current collector.

[0143] The method for manufacturing the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using methods for forming layers or films commonly used in the industry. For example, methods such as crimping, coating, and vapor deposition can be used. Furthermore, the negative electrode of the present invention is also included in the case where a metallic lithium thin film is formed on a metal plate by initial filling after the battery is assembled without a lithium thin film on the negative electrode current collector.

[0144] On the other hand, 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.

[0145] Specific examples of the aforementioned devices include, but are not limited to, power tools powered by electric motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0146] The following examples are provided to facilitate understanding of the invention, but these examples are provided only to make the invention easier to understand, and the invention is not limited thereto. [Examples]

[0147] Examples [Examples]

[0148] Example 1: Manufacturing of electrolytes and solid-state batteries Stage 1) Production of polymers including copolymers A polyethylene oxide (PEO) copolymer of the following chemical formula 1a was prepared: [ka] In the above chemical formula 1a, R1 is -CH2-O-(CH2-CH2-O) k The copolymer was -CH3, R2 was -CH2-O-CH2-CH=CH2, k was 2, the l:m:n ratio was 85:13:2, and the weight-average molecular weight (Mw) of the copolymer was approximately 2,000,000 g / mol.

[0149] The copolymer of chemical formula 1a has an allyl group linked via a methylene oxide linker as a crosslinking functional group.

[0150] A mixed solution of the polyethylene oxide copolymer and ceramic compound was prepared by mixing the polyethylene oxide copolymer with acetonitrile as a solvent, trimethylolpropane trimethacrylate as a crosslinking agent, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound. This solution was then stirred for 24 hours using a magnetic bar. At this time, the composition of the mixed solution of polyethylene oxide copolymer and ceramic compound was prepared by mixing 100 parts by weight of polyethylene oxide copolymer with 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, so that the concentration of polyethylene oxide copolymer in the mixed solution was 11.1% by weight, and the concentration of polyethylene oxide copolymer and ceramic compound in the mixed solution was 14.9% by weight using acetonitrile solvent.

[0151] After casting the prepared mixed solution onto the lower substrate of the coin cell, it was subjected to primary drying at room temperature for 12 hours, followed by secondary drying in a vacuum oven at 100°C for 12 hours to produce an electrolyte film with a thickness of 200 μm.

[0152] Phase 2) Manufacturing of electrolytes The polymer was attached to the upper plate of the chamber, and 50 μl of ethyl methyl carbonate (EMC) solvent was filled into the lower part of the chamber. The chamber was then allowed to evaporate naturally at room temperature for 72 hours, during which time the EMC vapor was introduced into the polymer attached to the upper part of the chamber, causing it to be deposited onto the polymer and thus producing the electrolyte.

[0153] Stage 3) Manufacturing of solid-state batteries (electrode assemblies) NCMA (LiNi 0.85 Co 0.05 Mn 0.08 Al 0.02O2) Cathode active material particles (particle size: 5-10 μm, LG CHEM, Republic of Korea), superconductive carbon (C-65) conductive material, cross-linked PEO copolymer of chemical formula 1a used in the first step, and LiTFSI were added in a weight ratio of 77.6:3:14.2:5.2 with acetonitrile as the solvent, and stirred using a paste mixer at 1500 rpm / 3 min for 5 times at room temperature. The prepared mixed solution was cast onto aluminum foil, and after primary drying at room temperature for 6 hours, it was secondary drying at 100°C for 12 hours to produce a 60 μm thick cathode film. The cathode film was subjected to a concentration of 6.712 mg / cm². 2 After punching out using mass loading, the manufactured composite solid electrolyte was used as an electrolyte film, and a lithium metal foil (300 μm) was used as the negative electrode. After lamination in a sandwich type, a coin cell was fabricated. [Examples]

[0154] Example 2: Manufacturing of electrolytes and solid-state batteries In the second step of Example 1, the polymer was attached to the upper plate of the chamber, 300 μl of ethyl methyl carbonate (EMC) solvent was filled into the lower part of the chamber, and then it was allowed to evaporate naturally at room temperature for 72 hours. EMC vapor was then introduced into the polymer attached to the upper part of the chamber to deposit onto the polymer, thereby producing an electrolyte.

[0155] The remaining steps were carried out in the same manner as in Example 1 to produce the electrolyte and solid battery.

[0156] Comparative example: Comparative Example 1: Manufacturing of electrolytes and solid-state batteries The electrolyte and solid battery were manufactured in the same manner as in Example 1, except that the second step of Example 1, which is the vapor deposition of the EMC solvent, was omitted.

[0157] Comparative Example 2: Electrolyte and battery manufacturing (containing a large amount of polar solvent) In the second step of Example 1, the electrolyte was prepared in the same manner as in Example 1, except that the liquid solvent was directly injected without vapor deposition of the EMC solvent. The EMC solvent was directly injected so that its content relative to the total weight of the prepared electrolyte was 12% by weight.

[0158] The remaining steps were carried out in the same manner as in Example 1 to produce the electrolyte and battery.

[0159] Experimental example Experimental Example 1: Measurement of Polar Compound Content The content of polar compounds can be measured by monitoring the weight of the liquid phase that evaporates over time while heating a solid electrolyte test specimen using a balance. For example, a heated electronic balance (AND's MS-70) can be used to measure the content by monitoring the weight of the liquid phase that evaporates over time while heating the test specimen from a temperature of 55°C and gradually increasing the temperature. When the amount of polar compounds evaporated over time reaches a saturation point, that saturation amount was considered to be the total amount of polar compounds contained in the solid electrolyte. In the examples and comparative examples, the polar compound was ethyl methyl carbonate (EMC; boiling point: approximately 101°C), and the heating process for measuring the content of the polar compound proceeded to approximately 110°C.

[0160] Table 1 below shows the measurement results of the EMC content deposited (or contained) in the electrolyte. [Table 1] Experimental Example 2: Measurement of Ionic Conductivity of Electrolytes To measure the ionic conductivity of the electrolytes prepared in the examples and comparative examples, 1.7671 cm⁻¹ was used. 2 After forming the electrolyte on the lower substrate of a coin cell of a certain size, a coin cell for measuring ionic conductivity was manufactured using SUS (Steel Use Stainless) as an inert electrode (blocking electrode).

[0161] Using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument), the resistance was measured at 25°C under conditions of an amplitude of 10mV and a scan range from 1Hz to 0.1MHz. The ionic conductivity of the electrolyte was then calculated using Equation 4 below.

number

[0162] Experimental Example 3: Measurement of Activation Energy of Electrolyte Layer at Different Temperatures Ionic conductivity of electrolyte film at different temperatures (σ i ) was measured using the same method as in Experimental Example 2. Based on the measurement results, log(σ) i The relationship between ) and 1000 / T (where T is the absolute temperature at which the ionic conductivity was measured) was fitted using the Arrhenius equation in Equation 3 below to derive Ea, which corresponds to the slope.

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[0163] Experimental Example 4: Evaluation of Thickness Deformation Rate during Rolling for the Positive Electrode The 60 μm thick positive electrode film manufactured in the example was passed through a roll-to-roll mill, and roll rolling was carried out to reduce the void ratio inside the electrode. The thickness of the positive electrode film was measured for each gap as the gap between the nip rolls of the mill was gradually reduced, and the ratio of the thickness of the positive electrode film to the thickness of the film before rolling was calculated for each roll gap. The calculated ratio of the gap between the rolls versus the thickness of the positive electrode film was subjected to regression analysis to determine the values ​​of C and n in Equation 2 below.

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[0164] Experimental Example 5: Charge and Discharge Tests for All-Solid-State Batteries To evaluate the galvanostatic cycling characteristics of the solid batteries manufactured in the above examples and comparative examples, charge-discharge tests were performed on the solid batteries in the voltage range of 3.0V to 4.25V using a TOSCAT charge-discharge tester (manufactured by TOYO Systems Co., Ltd.). For the solid batteries manufactured in the examples, charge-discharge tests were performed at room temperature (25°C) with a charge-discharge rate of 0.03C. After reaching a cut-off voltage of 4.25V, additional CV (constant voltage) charging was performed under a cut-off current condition of 0.01C. Additionally, for the solid batteries containing the solid electrolyte of the comparative examples, charge-discharge tests were performed at 25°C and 60°C, respectively, with a charge-discharge rate of 0.03C.

[0165] First, the evaluation results of the ionic conductivity for each electrolyte in the examples and comparative examples measured in the above examples are summarized in Table 2 below. [Table 2] Furthermore, from the measurement and evaluation results of Experimental Examples 2 and 3, the activation energy and log(σ) of the electrolyte layer included in Example 1 and Comparative Example 1 at different temperatures were obtained. i The results of the evaluation are shown in comparison with Figure 1. Referring to Figure 1, it was confirmed that the electrolyte of Example 1 had an activation energy deviation (ΔEa) of 0.02 eV or less depending on the temperature, and that there was almost no change in activation energy and ionic conductivity in response to changes in absolute temperature, as well as excellent ionic conductivity at all temperatures. In contrast, the electrolyte of Comparative Example 1 showed a large change in activation energy and ionic conductivity in response to changes in absolute temperature, and in particular, it was confirmed that it showed a rapid decrease in ionic conductivity in the low-temperature range and relatively poor ionic conductivity.

[0166] Furthermore, based on the evaluation results of Experimental Example 4, the degree of thickness deformation when the positive electrode included in Example 1 was rolled using a roll was evaluated and is shown in Figure 2. Referring to Figure 2, it was confirmed that the positive electrode film included in the battery of Example 1 exhibits excellent processability, as the thickness of the positive electrode film decreases almost inversely proportional to the gap between the rolls during the rolling process. In addition, based on Figure 2, it became possible to manufacture a positive electrode with a constant porosity and elastic recovery rate, minimizing errors caused by the positive electrode during performance evaluation of solid-state batteries and allowing only the influence corresponding to the physical properties of the solid electrolyte to be grasped.

[0167] In addition, based on the evaluation results of Experimental Example 5, Figure 3 shows the room temperature charge / discharge test results for the solid-state battery of Example 1, and Figure 4 shows the room temperature and high temperature (60°C) charge / discharge test results for the solid-state battery of Comparative Example 1.

[0168] Referring to Figures 3 and 4, the solid-state battery of the example exhibits excellent charge-discharge characteristics at room temperature due to being manufactured with a solid electrolyte having a high ionic conductivity of 1.3 mS / cm, whereas the solid-state battery of the comparative example is practically inoperable at room temperature due to the low ionic conductivity of the installed solid electrolyte, and is only capable of high-temperature operation above 60°C, similar to a typical all-solid-state battery containing 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 containing a PEO (polyethylene oxide) copolymer having crosslinkable functional groups, at least a portion of which form crosslink bonds; a ceramic compound; and a polar compound, wherein the polar compound is dispersed or bonded on the polymer. The positive electrode comprises a positive electrode active material and a binder containing a PEO-based copolymer having crosslinking functional groups. A solid-state battery in which the content of the polar compound is 0.1% by weight or more and less than 10% by weight, based on the total weight of the electrolyte layer.

2. The solid battery according to claim 1, wherein the polar compound is dispersed between the polymer chains forming the crosslinking bonds, or is adsorbed or bonded to the surface or interior of the polymer chains.

3. The solid battery according to claim 1, wherein at least a portion of the crosslinking functional groups form crosslink bonds with each other via a crosslinking agent.

4. The crosslinkable functional group is bonded to the PEO copolymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (wherein the alkylene linker having 0 carbon atoms shows a single bond). A solid battery according to claim 1, comprising a 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.

5. The solid battery according to claim 1, wherein at least one of the electrolyte layer or the positive electrode further comprises a lithium salt.

6. The solid battery according to claim 1, wherein the PEO (polyethylene oxide) copolymer is a copolymer containing repeating units of the following chemical formulas 1 to 3: 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 In the above chemical formulas 1 to 3, R １ is, -CH ２ -O-(CH ２ -CH ２ -O) ｋ -R ３ This shows that k is between 0 and 20, and R ３ This represents an alkyl group having 1 to 5 carbon atoms. R ２ This refers to a substituent in which one or more crosslinking functional groups selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, nitro groups, cyano groups, amine groups, amide groups, epoxy groups, and allyl groups are bonded to the polymer chain via a C0-C10 alkylene linker or alkylene oxide linker (where the C0 alkylene linker shows a single bond). l, m, and n are the number of repetitions in the repeating unit, where l and n are independent integers between 1 and 100,000, and m is an integer between 0 and 100,000.

7. The solid battery according to claim 1, wherein the polar compound comprises one or more selected from the group consisting of carbonate compounds and sulfonyl compounds.

8. The solid battery according to claim 1, wherein the ceramic compound comprises an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphorus oxide.

9. The electrolyte layer has a temperature-dependent activation energy difference (ΔEa) defined by the following formula 1, which is 0.03 eV or less, as described in claim 1, for the solid battery: [Math 1] In the above formula (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°C to 80°C. ΔE ａ represents the activation energy difference by temperature defined by the difference between the two activation energies.

10. The positive electrode satisfies the thickness deformation rate defined by the following formula 2 when rolled on both sides using a roll, according to claim 1 of the solid battery: [Math 2] In the above formula 2, δ ０ and d ０ δ represents the initial roll gap and initial thickness of the positive electrode before rolling, δ and d represent the roll gap and thickness of the positive electrode during rolling, and C and n are constants determined by regression analysis.

11. The solid battery according to claim 1, wherein the negative electrode includes a lithium metal layer.

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