Cell for electrolyte, electrolyte for secondary battery including same, method for preparing same, and lithium secondary battery including same

Abstract

A monomer for an electrolyte according to an embodiment of the present disclosure may include a compound represented by Formula 1. A lithium secondary battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, and an electrolyte, and the electrolyte may include a polymer formed by polymerizing a compound represented by Formula 1.

Description

Technical Field

[0001] This disclosure relates to a monomer for use as an electrolyte, an electrolyte for secondary batteries including the monomer, a method for preparing the electrolyte, and a lithium secondary battery including the electrolyte. Background Technology

[0002] A rechargeable battery is a type of battery that can be repeatedly charged and discharged. With the rapid development of information and communication technologies and the display industry, rechargeable batteries have been widely used as power sources for various portable electronic communication devices such as cameras, mobile phones, and laptops. Recently, battery packs utilizing rechargeable batteries have also been developed and are used as power sources for environmentally friendly vehicles, such as electric vehicles and hybrid vehicles.

[0003] Examples of rechargeable batteries include lithium-ion batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium-ion batteries have advantages in terms of high operating voltage and high energy density per unit weight, as well as fast charging speed and lightweight design. In this regard, lithium-ion batteries have been actively developed and applied in various industrial fields.

[0004] Commercially available lithium-ion batteries primarily utilize liquid-based electrolytes. However, sudden environmental changes, such as temperature fluctuations and external shocks, can lead to leaks, fires, and explosions, posing potential safety hazards. To address these issues, solid-state electrolytes are being developed to enhance stability and increase energy density.

[0005] The all-solid-state battery may include solid electrolytes such as gel polymers, oxides, sulfides or composite polymers as electrolytes to enhance stability against fire and explosion caused by external impacts or fluctuations in the external environment.

[0006] However, solid-state batteries that include some liquid may pose a higher risk of fire compared to all-solid-state batteries. Therefore, there is a need in the art to address the issues related to the use of liquid electrolytes in secondary batteries. Summary of the Invention

[0007] This document provides an electrolyte with improved flame retardancy, and in some embodiments, an electrolyte with improved ion conductivity. This document also provides a method for preparing such an electrolyte for secondary batteries. This document further provides a lithium secondary battery with improved stability and electrochemical properties.

[0008] In one embodiment, the electrolyte is prepared from a monomer for electrolytes, such as a compound represented by Formula 1.

[0009]

[0010] in:

[0011] R1 is a substituted or unsubstituted C6-C12 aromatic hydrocarbon group, or a group represented by *-R4-R5;

[0012] R2 and R3 are each independently a substituted or unsubstituted C1-C6 alkylene group, or a substituted or unsubstituted C1-C7 alkylene group;

[0013] R4 is a C3-C12 alkylene group in which at least one hydrogen atom is replaced by a fluorine atom;

[0014] R5 is an aggregateable functional group;

[0015] * indicates a bond to an adjacent oxygen atom;

[0016] R6 and R7 are each independently hydrogen or C1-C5 alkyl;

[0017] m and p are each independently 0-10; and

[0018] n is 0 or 1.

[0019] In some embodiments, R1 is a substituted or unsubstituted C6-C10 aromatic hydrocarbon group, or a group represented by *-R4-R5, wherein R5 is a polymerizable group, such as (meth)acrylate group.

[0020] In some embodiments, R1 is a phenyl group, or *-R4-R5, wherein R4 is a C3-C6 alkylene group in which at least one hydrogen atom is replaced by a fluorine atom.

[0021] In some embodiments, R2 and R3 are each independently an unsubstituted or fluorinated C1-C3 alkylene group, or a fluorinated C1-C5 oxyalkylene group.

[0022] In some embodiments, R1 is a substituted or unsubstituted C6-C10 aryl group; and R2 and R3 are each independently an unsubstituted or fluorinated C1-C3 alkylene group, or a fluorinated C1-C5 oxyalkylene group; or *-R4-R5, wherein R5 is a (meth)acrylate group.

[0023] In some implementations, n is 1.

[0024] In some embodiments, the electrolyte comprises a polymer product of one or more monomers, each independently represented by formula 1-1, formula 1-2, and formula 1-3:

[0025]

[0026]

[0027] A flame retardant compound can be formed by polymerizing one or more monomers for an electrolyte according to any embodiment. The flame retardant compound and a lithium salt can be incorporated into an electrolyte for a secondary battery.

[0028] In some embodiments, the electrolyte is a composite electrolyte comprising a porous matrix, which may include organic polymers and inorganic electrolytes. In some embodiments, the inorganic electrolyte comprises an oxide-based solid electrolyte.

[0029] In some embodiments, the electrolyte comprises about 1% to about 30% by weight of the flame retardant compound, based on the total weight of the electrolyte. In some embodiments, the electrolyte comprises about 1% to about 15% by weight of the flame retardant compound, based on the total weight of the electrolyte. In some embodiments, the electrolyte comprises about 5% to about 15% by weight of the flame retardant compound, based on the total weight of the electrolyte.

[0030] A lithium secondary battery prepared using the electrolyte described herein may include: a positive electrode; a negative electrode disposed opposite to the positive electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, as well as the electrolyte described herein.

[0031] An electrolyte for a secondary battery according to an exemplary embodiment can be prepared by preparing a first mixed solution comprising one or more monomers for the electrolyte (e.g., compounds represented by any one or more of formulas 1-1, 1-2, and 1-3) and an electrolyte solution. The first mixed solution can then be cured to prepare the electrolyte.

[0032] In some embodiments, such as those employing porous membranes, the first mixed solution may further comprise an organic polymer and an inorganic electrolyte. In some embodiments, the inorganic electrolyte comprises an oxide-based solid electrolyte.

[0033] In some embodiments, based on the total weight of the first mixed solution, the first mixed solution includes about 1% to about 30% by weight, or about 1% to about 20% by weight, or about 5% to about 15% by weight of monomers for electrolytes.

[0034] In some embodiments, the monomer includes thermally reactive functional groups, the first mixed solution further includes a thermal initiator, and the curing includes heat treatment of the first mixed solution.

[0035] In some embodiments, the monomer includes a photoreactive functional group, the first mixed solution further includes a photoinitiator, and the curing includes irradiating the first mixed solution with light.

[0036] Electrolytes for secondary batteries can be prepared by using the monomers disclosed herein, which can have improved ignition stability, and thus secondary batteries prepared therefrom can be self-extinguishing. Attached Figure Description

[0037] The above and other objects, features and advantages of this disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0038] Figure 1 This is a schematic diagram illustrating the structure of an electrolyte layer for a secondary battery according to an exemplary embodiment;

[0039] Figure 2 This is a schematic flowchart illustrating a method for preparing an electrolyte for a secondary battery according to an exemplary embodiment.

[0040] Figure 3 A schematic cross-sectional view is provided to illustrate an electrode unit according to an exemplary embodiment. Detailed Implementation

[0041] According to exemplary embodiments, an electrolyte cell, a method for preparing an electrolyte for a secondary battery comprising the electrolyte cell, and an electrolyte for a secondary battery prepared by the method are provided. Furthermore, a lithium secondary battery comprising an electrolyte layer containing an electrolyte for a secondary battery is also provided.

[0042] The embodiments of this disclosure will now be described in detail. However, these are merely illustrative examples, and this disclosure is not limited to the specific embodiments described by way of example.

[0043] Unless otherwise defined in this disclosure, when a part, such as a layer, membrane, film, region, or plate, is described as existing "on" or "above" another part, it includes not only the case where the part is "directly on" the other part, but also the case where there are other parts between them.

[0044] If the compound represented by the formula used in this article has isomers, then the formula refers to both the compound being described and all its isomers.

[0045] As used herein, the term "polymerizable functional group" refers to a functional group capable of undergoing polymerization reactions with other compounds, such as a functional group containing a carbon-carbon double bond. For example, the polymerizable functional group may include (meth)acrylate, vinyl, allyl, etc.

[0046] The term “substituted or unsubstituted Ca-Cb Y group” as used in this article refers to an unsubstituted Y group having ab carbon atoms, excluding the number of carbon atoms of substituents that substituted the Y group.

[0047] As used herein, the term "aromatic hydrocarbon group" refers to a functional group that is aromatic in its entirety, or a functional group that contains an aromatic ring (e.g., a benzene ring). "Aromatic hydrocarbon group" may include, for example, substituted or unsubstituted aryl (C6-C12), substituted or unsubstituted arylalkyl (C6-C12), substituted or unsubstituted alkylaryl (C6-C12), etc.

[0048] As used herein, the term "oxyalkylene" refers to a functional group in a straight-chain or branched saturated hydrocarbon in which any methylene (-CH2-) group is replaced by an oxygen atom, and may include, for example, a functional group consisting of "-OC". n H 2n -" or "C" n H 2n -OC n H 2n -” indicates an oxy-alkylene structure.

[0049] As used herein, the term “substituted” can refer to a compound in which at least one hydrogen atom is substituted by a substituent such as a halogen group, hydroxyl group, heteroalkyl (C1-C5), heterocycloalkyl (C1-C5), heteroaryl (C6-C12), amino group, nitrile group, nitro group, silyl group, etc.

[0050] As used herein, the terms “heteroalkyl,” “heterocyclic alkyl,” and “heteroaryl” refer to groups in which at least one carbon atom of an alkyl, cycloalkyl, or aryl group is substituted by at least one of nitrogen, oxygen, or sulfur.

[0051] The term "unsubstituted" as used in this article refers to compounds in which none of the hydrogen atoms have been substituted.

[0052] The term "unsubstituted alkylene" as used in this article refers to a saturated hydrocarbon group in which none of the hydrogen atoms are replaced by other atoms or molecules.

[0053] As used in this article, the term "fluorine-substituted" refers to a compound in which at least one hydrogen atom is substituted by fluorine (F).

[0054] The term "flame retardancy" as used in this article refers to the property of preventing or inhibiting combustion; that is, a sample burns when in contact with a flame (ignition source), but self-extinguishes once the flame is removed. This flame retardancy can be assessed by applying a flame of sufficient heat to the sample with a torch for one second or longer, then removing the torch and measuring the time required for the flame to extinguish. The shorter the time required for the flame to extinguish, the better the flame retardancy.

[0055] Specifically, the term "flame retardant compound" as used herein can refer to a compound in which, after glass fiber cut to 16 pi is impregnated with a flame retardant compound and cured as needed, it is ignited by a flame supplied with a certain amount of heat by a torch for 1 second or longer, and then the torch is removed, at which point the extinguishing time (s / g) of the compound relative to the sample mass is 100 s / g or less, for example 95 s / g or less.

[0056] An example of an electrolyte cell that can be used to manufacture electrolytes for secondary batteries is represented by the following formula 1.

[0057]

[0058] In an exemplary embodiment, in Formula 1, R1 is a substituted or unsubstituted C6-C12, C6-C10, or C6-C8 aromatic hydrocarbon group. Therefore, the flame retardancy of electrolytes comprising polymers or copolymers of compounds represented by Formula 1 can be improved.

[0059] In some embodiments, R1 is a substituted or unsubstituted C6-C12, C6-C10, or C6-C8 aryl group. For example, R1 can be a substituted or unsubstituted phenyl, benzyl, tolyl, xylyl, naphthyl, etc. In some embodiments, R1 is an unsubstituted phenyl group. In some embodiments, introducing an aryl group at the R1 position of the compound represented by Formula 1 can improve the heat resistance and structural stability of the polymer or copolymer formed from the compound represented by Formula 1.

[0060] In other embodiments, R1 is *-R4-R5, where * indicates a bond to an adjacent oxygen atom. In some embodiments, R4 is a C3-C12 alkylene group in which at least one hydrogen atom is substituted with a fluorine atom. For example, R4 can be a C3-C10, C3-C8, or C3-C6 alkylene group in which at least one hydrogen atom is substituted with a fluorine atom. In some embodiments, introducing fluorocarbons at the R1 position of the compound represented by Formula 1 can improve the heat resistance and structural stability of polymers or copolymers formed from the compound represented by Formula 1.

[0061] In some embodiments, R1 is a substituted or unsubstituted C6-C10 aromatic hydrocarbon group, or *-R4-R5, wherein R4 is a C3-C12 alkylene group in which at least one hydrogen atom is substituted by a fluorine atom, R5 is a (meth)acrylate group, and * indicates a bond to an adjacent oxygen atom.

[0062] In some embodiments, R1 is phenyl, or *-R4-R5, wherein R4 is a C3-C6 alkylene group in which at least one hydrogen atom is replaced by a fluorine atom, R5 is a (meth)acrylate group, and * indicates a bond to an adjacent oxygen atom.

[0063] In some embodiments, R5 is a polymerizable functional group. For example, R5 may contain an acrylate group, a vinyl group, or an allyl group. In some embodiments, R5 contains a (meth)acrylate group. In some embodiments, introducing a polymerizable functional group at the R1 position allows for more extensive polymerization of the electrolyte monomer and the formation of a denser network polymer, thereby further improving flame retardancy.

[0064] Therefore, the compound represented by Formula 1 above may include two or more polymerizable groups, such as (meth)acrylate groups, for example when R5 contains (meth)acrylate groups. In such embodiments, the compound of Formula 1 may be a thermosetting or photosetting material, and the electrolyte comprising the polymer or copolymer formed by the compound represented by Formula 1 may be a crosslinked polymer or a network polymer, which may be formed by thermosetting or photosetting techniques, which may further improve the flame retardancy of the electrolyte comprising the polymer or copolymer formed by the compound represented by Formula 1.

[0065] In exemplary embodiments, in Formula 1, R2 and R3 are each independently a substituted or unsubstituted C1-C6 alkylene, or a substituted or unsubstituted C1-C7 alkylene containing one, two, or three oxygen atoms. For example, R2 and R3 may each be independently an unsubstituted or fluorinated C1-C5, C1-C4, or C1-C3 alkylene. As another example, R2 and R3 may each be independently a fluorinated C1-C5, C1-C4, or C1-C3 alkylene. As yet another example, R2 and R3 may each be independently an unsubstituted or fluorinated C3-C7 alkylene containing one or two oxygen atoms. In some embodiments, each hydrogen atom in the fluorinated alkylene or alkylene is substituted with fluorine. In other embodiments, at least 80% of the hydrogen atoms in the fluorinated alkylene or alkylene are substituted with fluorine. In still other embodiments, at least 50% of the hydrogen atoms in the fluorinated alkylene or alkylene are substituted with fluorine.

[0066] In some embodiments, R2 and R3 are each independently an unsubstituted or fluorinated C1-C3 alkylene group, or a fluorinated C1-C5 oxyalkylene group. Therefore, the flame retardancy of the electrolyte in the polymer or copolymer containing the compound represented by Formula 1 can be further improved.

[0067] In some embodiments, the introduction of alkylene or oxyalkylene groups, particularly those that are at least partially fluorinated, at the R2 and R3 positions of the compounds represented by Formula 1 can improve the flame retardancy and self-extinguishing properties of electrolytes comprising polymers or copolymers formed from compounds represented by Formula 1. Furthermore, the oxygen atom in the oxyalkylene group can further promote the dehydration reaction of polymethionine and the formation of carbon compounds.

[0068] In exemplary embodiments, m and p are each independently 0-10. In some embodiments, p and n are each 2. In some embodiments, p and n are each 0.

[0069] In other embodiments, R6 and R7 are each independently hydrogen or C1-C5 alkyl. For example, in some embodiments, one or both of R6 and R7 are hydrogen. For example, in other embodiments, R6 and R7 are independently hydrogen or methyl.

[0070] The compounds represented by Formula 1 above contain phosphorus in the form of phosphate ester groups or phosphonate ester groups. Without being bound by any particular theory, the introduction of phosphorus into the compounds of Formula 1 facilitates thermal decomposition upon ignition, thereby generating poly(methoxyphosphoric acid). With the formation of poly(methoxyphosphoric acid), carbon compounds (e.g., char) are generated through dehydration, esterification, and dehydrogenation reactions of the poly(methoxyphosphoric acid). The poly(methoxyphosphoric acid) can form a protective layer, and the carbon compounds can form a carbon film; therefore, materials formed from the compounds represented by Formula 1 above, such as polymers, can block oxygen and heat under high-temperature conditions and prevent ignition and combustion. Therefore, electrolytes containing polymers or copolymers formed from the compounds represented by Formula 1 above can exhibit excellent self-extinguishing properties. These properties can be further improved by increasing the phosphorus content in the compounds represented by Formula 1 to further promote the formation of poly(methoxyphosphoric acid) and carbon compounds upon ignition.

[0071] In an exemplary embodiment, n is 0 or 1. For example, n can be 1, and the compound represented by Formula 1 contains phosphate ester groups to promote the formation of polymethionine and carbon compounds and improve the self-extinguishing properties of electrolytes containing polymers or copolymers formed from the compound.

[0072] In some embodiments of Formula 1, R1 is a substituted or unsubstituted C6-C10 aryl group; R2 and R3 are each independently an unsubstituted or fluorinated C1-C3 alkylene group or a fluorinated C1-C5 oxyalkylene group; or R1 is *-R4-R5, wherein R4 is a C3-C12 alkylene group in which at least one hydrogen atom is substituted by a fluorine atom, R5 is a (meth)acrylate group, and * indicates a bond to an adjacent oxygen atom.

[0073] In exemplary embodiments, the compound represented by Formula 1 may include its equivalents. For example, at least one hydrogen atom in Formula 1 bonded to a carbon atom may be further replaced by one or more portions that are considered chemically equivalent or similar by those skilled in the art; for example, at least one hydrogen atom in Formula 1 bonded to a carbon atom may be further replaced by deuterium or an alkyl group having 1 to 5 carbon atoms.

[0074] Furthermore, unintended chain ignition of electrolytes can be promoted by free radicals (e.g., hydrogen radicals) generated by ignition of organic solvents. Without being bound by any particular theory, it is believed that the phosphorus atoms contained in the compounds represented by Formula 1 help to suppress chain ignition by scavenging free radicals (e.g., hydrogen radicals). Therefore, electrolytes containing the compounds represented by Formula 1 above and their polymers or copolymers can have high self-extinguishing properties and improved flame retardancy.

[0075] In one embodiment, the compound represented by Formula 1 may be represented by the following Formula 1-1.

[0076]

[0077] The compound represented by Formula 1-1 above contains a phenyl group at the R1 position, a fluorinated oxyalkylene group at the R2 and R3 positions, and a phosphonate group. Therefore, the electrolyte of the polymer or copolymer containing the compound represented by Formula 1-1 can have improved flame retardancy, thereby effectively suppressing any chain ignition caused by temperature rise or ignition conditions.

[0078] The electrolyte for secondary batteries can be prepared from a compound represented by Formula 1-1 or any equivalent thereof. For example, at least one hydrogen atom bonded to a carbon atom in Formula 1-1 may be further replaced by one or more portions that are considered chemically equivalent or similar by those skilled in the art; for example, at least one hydrogen atom bonded to a carbon atom in Formula 1-1 may be further replaced by deuterium or an alkyl group having 1 to 5 carbon atoms.

[0079] In one embodiment, the compound represented by Formula 1 may be a compound represented by Formulas 1-2 below, and thus can be used to manufacture an electrolyte for secondary batteries.

[0080]

[0081] The compounds represented by Formula 1-2 contain a phenyl group at the R1 position, contain a phosphate ester group, and have a higher phosphorus content, for example, compared to the compounds of Formula 1-1. Therefore, electrolytes containing polymers or copolymers formed from compounds represented by Formula 1-2 are able to more effectively form a phosphorus-derived protective layer and further suppress chain ignition reactions.

[0082] The electrolyte for secondary batteries can be prepared from compounds represented by formulas 1-2 or any equivalent thereof. For example, at least one hydrogen atom bonded to a carbon atom in formulas 1-2 may be further replaced by one or more portions that are considered chemically equivalent or similar by those skilled in the art; for example, at least one hydrogen atom bonded to a carbon atom in formulas 1-2 may be further replaced by deuterium or an alkyl group having 1 to 5 carbon atoms.

[0083] In one embodiment, the compound represented by Formula 1 can be a compound represented by Formulas 1-3 below, and thus can be used to manufacture an electrolyte for secondary batteries.

[0084]

[0085] The compounds represented by Formulas 1-3 contain three acrylate groups, fluorinated alkylene groups at R2 and R3 positions, and phosphonate groups. Therefore, electrolytes containing polymers or copolymers of compounds represented by Formulas 1-3 can have a dense cross-linked structure, further improving their flame retardancy and suppressing chain ignition. Thus, electrolytes containing polymers or copolymers formed from compounds represented by Formulas 1-3 can have a denser cross-linked structure (e.g., compared to compounds of Formulas 1-1 or 1-2) and can more effectively suppress chain ignition reactions.

[0086] The electrolyte for secondary batteries can be prepared from compounds represented by formulas 1-3 or any equivalent thereof. For example, at least one hydrogen atom bonded to a carbon atom in formulas 1-3 may be further replaced by one or more portions that are considered chemically equivalent or similar by those skilled in the art; for example, at least one hydrogen atom bonded to a carbon atom in formulas 1-3 may be further replaced by deuterium or an alkyl group having 1 to 5 carbon atoms.

[0087] In some embodiments, the compounds represented by Formula 1-1, Formula 1-2, and Formula 1-3 may be used as electrolyte monomers in two or more combinations (e.g., to generate flame-retardant copolymers). The copolymers may be block copolymers or random copolymers. The polymers or copolymers formed from one or more monomeric compounds represented by Formula 1-1, Formula 1-2, and Formula 1-3 may be cross-linked and / or network polymers or copolymers. The flame retardancy of the electrolyte containing the polymers can be improved by generating polymers and copolymers from the monomeric compounds represented by Formula 1-1, Formula 1-2, and Formula 1-3. In some embodiments, the electrolyte does not contain any trimethylolpropane ethoxylate triacrylate.

[0088] Figure 1 An exemplary embodiment of an electrolyte 100 comprising a flame retardant compound 110 is shown. The flame retardant compound 110 may comprise, for example, the polymer described above or be composed thereof, to suppress side reactions between the flame retardant compound 110 and the electrolyte 100. Furthermore, the flame retardant compound 110 may contain fluorine- or phosphorus-containing functional groups to block oxygen during combustion and prevent thermal runaway.

[0089] In some embodiments, the flame retardant compound 110 comprises, or is composed of, a polymer or copolymer of one or more electrolyte monomers having thermally reactive and / or photoreactive functional groups. For example, a suitable electrolyte monomer may include an acrylate group, which may function as a thermally reactive or photoreactive functional group, as in the cases of Formulas 1-3.

[0090] In some embodiments, flame retardant compound 110 comprises or is composed of a polymer of a compound represented by Formula 1. For example, the polymer can be formed by polymerizing the (meth)acrylate group in the compound represented by Formula 1 and / or by polymerizing the (meth)acrylate group in the compound represented by Formula 1 with the polymerizable functional group at the R5 position in the compound represented by Formula 1.

[0091] In one embodiment, the flame retardant compound comprises a compound represented by Formula 2.

[0092]

[0093] In Formula 2, R1, R2, R3, R6, R7, m, n, and p can be the same as those described above with respect to Formula 1. For example, the electrolyte may contain a flame-retardant compound comprising, or consisting of, a cross-linked polymer or network polymer represented by Formula 2 as a unit structure.

[0094] The electrolyte for a secondary battery may comprise a unit structure represented by Formula 2 or any equivalent thereof. For example, at least one hydrogen atom bonded to a carbon atom in Formula 2 may be further replaced by one or more portions that are considered chemically equivalent or similar by those skilled in the art; for example, at least one hydrogen atom bonded to a carbon atom in Formula 2 may be further replaced by deuterium or an alkyl group having 1 to 5 carbon atoms.

[0095] In some embodiments, the electrolyte for secondary batteries (hereinafter also referred to as the “electrolyte”) according to an exemplary embodiment may comprise, or comprise, a flame retardant compound 110 (comprising or consisting of a polymer of one or more electrolyte monomers disclosed herein) and a lithium salt.

[0096] It can be represented as Li + X - The lithium salt anion can be selected from, for example, the group consisting of: F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 -(CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - In some implementations, LiPF6 is used as the lithium salt.

[0097] In some embodiments, the electrolyte comprises, based on its total weight, about 1 wt% (“wt%”) to about 30 wt%, about 3 wt% to about 30 wt%, about 5 wt% to about 25 wt%, about 5 wt% to about 20 wt%, or about 5 wt% to about 15 wt% of flame retardant compound 110. In some embodiments, the electrolyte comprises about 5 wt% to about 15 wt% of flame retardant compound. In some embodiments, the electrolyte comprises about 10 wt% to about 20 wt% of flame retardant compound. Within these ranges, the ionic conductivity of the electrolyte 100 can be improved, thereby imparting it with improved flame retardant properties.

[0098] In some embodiments, electrolyte 100 comprises, or is composed of, flame retardant compound 110 (as described herein), lithium salt, and electrolyte solution. In some embodiments, the electrolyte solution comprises an organic solvent. For example, the organic solvent may comprise carbonate organic solvents such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC), and vinylene carbonate (VC); or solvents such as dimethyl sulfoxide (DMSO), acetonitrile (ACN), dimethoxyethane (DME), diethoxyethane, sulfolane, gamma-butyrolactone (GBL), propylene sulfite, and tetrahydrofuran (THF). These can be used alone or in combination of two or more. In one embodiment, the organic solvent includes EC, EMC, or a mixture of both, as described in the examples. In one embodiment, the organic solvent is a carbonate-based organic solvent, which in some embodiments can impart improved electrical and chemical stability to the electrolyte for secondary batteries.

[0099] In one embodiment, the electrolyte solution may further comprise additives. Suitable additives may include cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulcolepsy compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, borate compounds, etc. Examples of suitable cyclic carbonate compounds include, but are not limited to, ethylene carbonate, vinyl ethylene carbonate (VEC), etc. Examples of suitable fluorinated cyclic carbonate compounds include, but are not limited to, fluoroethylene carbonate (FEC), etc. Examples of suitable sulcolepsy compounds include, but are not limited to, 1,3-propane sulcolepsy, 1,3-propene sulcolepsy, 1,4-butane sulcolepsy, etc. Examples of suitable cyclic sulfate compounds include, but are not limited to, 1,2-ethylene sulfate, 1,2-propylene sulfate, etc. Examples of suitable cyclic sulfite compounds include, but are not limited to, ethylene sulfite, butyl sulfite, etc. Examples of suitable phosphate compounds include, but are not limited to, lithium difluorobis(oxalate)borate, lithium difluorophosphate, etc. Examples of suitable borate compounds include, but are not limited to, lithium bis(oxalate)borate, etc.

[0100] In some embodiments, the electrolyte comprises, or is composed of, a flame retardant compound 110 (as described herein), a lithium salt, and an electrolyte solution. In some embodiments, the flame retardant compound is polymerized within a porous matrix, such as a porous polymer. In these embodiments, the flame retardant 110 is contained within the pores. In some embodiments, the porous polymer is a membrane. Methods for preparing membranes are well known to those skilled in the art. In some embodiments, the membrane comprises, or is composed of, polyethylene and / or polypropylene. In these embodiments, the reduction in electrolyte resistance results in improved ionic conductivity and flame retardancy of the electrolyte 100.

[0101] In some embodiments, the electrolyte comprises a porous composite electrolyte (PCE) containing a porous matrix. In such embodiments, the electrolyte comprises, or is composed of, a flame retardant compound 110 (as described herein), a lithium salt, an electrolyte solution, and the PCE. In some embodiments, the porous matrix is ​​a membrane. In some embodiments, the PCE is an organic polymer electrolyte (POPE). In such embodiments, the electrolyte may comprise, or is composed of, a flame retardant compound 110 (as described herein), a lithium salt, an electrolyte solution, and an organic polymer electrolyte (POPE). In some embodiments, the PCE may comprise an organic polymer and an inorganic electrolyte, or be prepared therefrom. In some embodiments, the inorganic electrolyte is physically bound within a porous matrix containing an organic polymer (e.g., polymerized within its pores).

[0102] The organic polymer may be an ion-conducting polymer. For example, the organic polymer may contain repeating units based on ether, styrene, or fluorinated hydrocarbon groups. In some embodiments, the organic polymer comprises at least one selected from the group consisting of: polyvinylidene fluoride (PVDF), polystyrene (PS), polyether sulfone (PES), polyurethane (PU), polyethylene oxide (PEO), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyimide (PI), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethyl methacrylate (PEMA), polycaprolactone (PCL), and polyvinyl pyrrolidone (PVP). In one embodiment, the organic polymer may comprise at least one selected from PVDF, PS, PES, and PU. In some embodiments, the use of ion-conducting polymers such as any of those described above can improve the conductivity and mobility of lithium ions within a porous matrix, thereby enhancing ion conductivity.

[0103] The inorganic electrolyte may be an oxide-based solid electrolyte, which, for example, contains ion-conducting compounds containing metals and / or oxygen. For example, a suitable oxide-based solid electrolyte may contain one or more LLTOs. TM (Lithium Lanthanum Titanium Oxide) compound; LLZO TM (Lithium Lanthanum Zirconium Oxide) compound; or LLZTO TM (Lithium Lanthanum Zirconium Tantalum Oxide) compounds, such as Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li6La2CaTa2O 12 Li6La2ANb2O 12 (where A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 Li9SiAlO8; LAGP TM (Lithium Aluminum Germanium Phosphate) compound; LATP TM (Lithium Aluminum Titanium Phosphate) compounds, such as Li 1+x Ti 2-x Al x Si y (PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiAl x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and LiTi x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1); LISICON TM (Lithium Super Ionic Conductor) compound, LIPON TM (Lithium Phosphorous OxyNitride) compounds, perovskite compounds, NASICON TM(Na Super Ionic Conductor) compounds or metal oxides, such as Al₂O₃, ZnO₂, Ce₂O₂, TiO₂, ZrO₂, HfO₂, MnO₂, MgO, WO₂, and V₂O₅. In one embodiment, the inorganic electrolyte is a lithium-containing oxide-based solid electrolyte, such as LLTO. TM Compounds, LLZO TM Compounds (e.g., garnet-type LLZO) TM (compound), LLZTO TM Compound, NASICON TM Compounds, LATP TM Compounds, perovskite compounds, etc. By using oxide-based solid electrolytes, such as lithium-containing oxide-based solid electrolytes, lithium dendrite growth can be suppressed, and the ionic conductivity and mechanical strength of electrolyte 100 can be improved, thereby enhancing the high-temperature stability and cycle life characteristics of the electrolyte.

[0104] Figure 2 This is an exemplary flow chart illustrating the process for preparing an improved electrolyte for secondary batteries according to this disclosure. Figure 2 In step S10, a first mixed solution is prepared. This first mixed solution comprises at least one or more electrolyte monomers (e.g., one or more monomers of Formula 1-1, Formula 1-2, and Formula 1-3), a lithium salt, and an electrolyte solution. In embodiments where the electrolyte further comprises PCE (Porous Composite Electrolyte) (such as POPE (Organic Polymer Electrolyte)), the PCE (or POPE) component may be incorporated into the first mixed solution, such that it comprises one or more electrolyte monomers (e.g., one or more monomers of Formula 1-1, Formula 1-2, and Formula 1-3), one or more lithium salts, an electrolyte solution, an organic polymer, and an inorganic electrolyte, or is composed thereof. In other embodiments, PCE (or POPE) may be prepared first and then added as a porous matrix to the first mixed solution, such that the first mixed solution comprises one or more electrolyte monomers (e.g., one or more monomers of Formula 1-1, Formula 1-2, and Formula 1-3), one or more lithium salts, an electrolyte solution, and PCE or POPE, or is composed thereof.

[0105] In an embodiment where a porous matrix is ​​first prepared and then added to a first mixed solution, the organic polymer, inorganic electrolyte, first solvent, and second solvent can be combined, and then the solvent can be removed.

[0106] There are no particular limitations on the types of the first and second solvents. In one embodiment, the organic polymer is soluble in the first solvent but insoluble in the second solvent. Therefore, the organic polymer is soluble in the first solvent but insoluble (or substantially insoluble) in the second solvent. In some embodiments, the first and second solvents are miscible. For example, the first and second solvents can be mixed or blended. Examples of suitable first solvents include, but are not limited to, THF, 2-methyltetrahydrofuran (2-Me-THF), N-methyl-2-pyrrolidone (NMP), 1,3-dioxolane, vinylene carbonate (VC), etc. These can be used alone or in combination of two or more. In one embodiment, the first solvent is or contains tetrahydrofuran. Examples of suitable second solvents include, but are not limited to, heptane, octane, nonane, decane, dodecane, 2,2,4-trimethylpentane, etc. These can be used alone or in combination of two or more. In one embodiment, the second solvent is or contains octane.

[0107] In some embodiments, solvent removal is performed by casting a second mixed solution onto a substrate (e.g., a glass substrate, a plastic substrate, etc.) and then heating it to remove the solvent.

[0108] In one embodiment, removing the solvent from the second mixed solution includes removing the first solvent at a first temperature and removing the second solvent at a second temperature. For example, the first solvent may be removed from the second mixed solution first, followed by the removal of the second solvent, to prepare a porous matrix. The removal of the first solvent and the removal of the second solvent may be performed sequentially, or the removal of the second solvent may be performed after a certain period of time following the removal of the first solvent. Therefore, the first solvent may be removed first, followed by the removal of the second solvent, to obtain a porous matrix that can be added to the first solution.

[0109] In some embodiments, such as in embodiments where one or more electrolyte monomers contain thermally reactive or photoreactive functional groups, the first mixed solution may further contain a thermal initiator and / or a photoinitiator, if appropriate. For example, based on 100 parts by weight of the first mixed solution, the first mixed solution may contain about 0.5 parts by weight (“wt parts”) to about 2 wt parts of a thermal initiator and / or a photoinitiator. Examples of suitable thermal initiators include, but are not limited to, azo compounds such as 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), 2,2'-azobisobutyronitrile (AIBN), azobisdimethyl-valeronitrile (AMVN), and dimethyl 2,2'-azobis(2-methylpropionic acid). 2,2'-azobis(2-methylpropionate)), 2,2'-azobis(2,4-dimethylvaleronitrile)), tert-butylperoxypivalate, di(3,5,5-trimethylhexanoyl)peroxide, tert-butylperoxy-2-ethylhexanoate, etc.; or peroxide compounds, such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, cumyl peroxide, hydrogen peroxide, etc. Examples of suitable photoinitiators include, but are not limited to, acylphosphine, such as 2-hydroxy-2-methyl-1-phenylpropan-1-one (HMPP), benzoin ether, dialkyl acetophenone, hydroxyalkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide, etc.; or α-amino ketone.

[0110] Still refer to Figure 2The first mixed solution can then be cured in step S20 to polymerize one or more electrolyte monomers, and if the organic polymer (as part of PCE or POPE) has not yet been polymerized, its polymerization is completed simultaneously. In some embodiments, the first mixed solution is combined with a porous membrane, such as a diaphragm, to impregnate the diaphragm, and then cured to generate a porous electrolyte structure disposed within the diaphragm structure.

[0111] In some embodiments, the weight percentage of the flame retardant compound in the electrolyte is substantially the same as the amount of electrolyte monomer contained in the first mixed solution. That is, in some embodiments, the weight change (decrease or increase) during the curing process of the first mixed solution is substantially negligible (e.g., an increase or decrease of about 0.0001 wt%, or about 0.00001 wt%, or less, based on the total weight of the electrolyte monomer).

[0112] The first mixed solution can be cured by any method known in the art. For example, in some embodiments, the first mixed solution is cured by heat treatment. There are no particular limitations on the temperature used to cure the first mixed solution. In some embodiments, the heat treatment temperature is about 30°C to about 120°C, about 60°C to about 100°C, or about 70°C to about 90°C. When used to describe temperature, “about” as used herein means ±5°C, provided that the temperature range provides the same results (e.g., no phase change or degradation within the covered temperature range). In some embodiments, the first mixed solution is subjected to heat treatment for about 20 minutes to about 3 hours, about 30 minutes to about 2 hours, or about 40 minutes to about 1.5 hours. Within the above temperature and time ranges, one or more electrolyte monomers contained in the first mixed solution can be sufficiently polymerized or copolymerized.

[0113] In other embodiments, the first mixed solution is cured by irradiating it with light. Therefore, the polymerization or copolymerization of one or more electrolyte monomers in the first mixed solution can be carried out at relatively low temperatures. In some embodiments, no heat source is applied during the curing of the first mixed solution; the only heat generated during the curing process originates from the irradiation. This prevents damage to the polymerized or copolymerized one or more electrolyte monomers that can sometimes occur during high-temperature heat treatment. There are no particular limitations on the wavelength, intensity, and duration of the irradiation used to cure the one or more electrolyte monomers in the first mixed solution, and these limitations depend on the specific type of electrolyte monomer. For example, in some embodiments, light with a wavelength of about 250 nm to about 400 nm is used to cure one or more electrolyte monomers. In some embodiments, the light intensity is about 800 mW / cm². 2 Approximately 1100 mW / cm 2In some embodiments, the first mixed solution containing one or more electrolyte monomers is exposed to light for about 5 seconds to about 20 seconds. Within the aforementioned wavelength, intensity, and irradiation time range, the one or more electrolyte monomers in the first mixed solution can be sufficiently polymerized or copolymerized to generate an electrolyte containing a suitable flame-retardant compound.

[0114] Electrolytes containing flame-retardant compounds having the properties of any of the embodiments disclosed herein and prepared by any of the embodiments may be incorporated into electrode units, such as electrode units of a secondary battery. Figure 3 This is a schematic cross-sectional view of an exemplary electrode unit 200 incorporating an electrolyte containing the flame retardant described herein. Figure 3 In the electrode unit 200, a positive electrode 240 may be included, a negative electrode 260 disposed opposite to the positive electrode 240, and an electrolyte layer 210 disposed between the positive electrode 240 and the negative electrode 260. The positive electrode 240 may include a positive electrode current collector 235 and a positive electrode active material layer 230 disposed on at least one surface of the positive electrode current collector 235.

[0115] The positive current collector 235 can be made of any material, such as stainless steel, nickel, aluminum, titanium, or any alloy thereof. The positive current collector 235 can also be made of aluminum or stainless steel with a surface treated with carbon, nickel, titanium, or silver. The thickness of the positive current collector 235 can be, for example, from about 10 μm to about 50 μm, but is not limited thereto.

[0116] The positive electrode active material 230 may comprise a compound capable of reversibly inserting and deintercalating lithium ions. In an exemplary embodiment, the positive electrode active material may comprise a lithium nickel metal oxide. The lithium nickel metal oxide may further comprise at least one metal selected from a combination of cobalt (Co), manganese (Mn), and aluminum (Al). In some embodiments, the positive electrode active material or the lithium nickel metal oxide may comprise a layered structure or a crystal structure represented by the following Formula 3.

[0117] Li x Ni a M b O 2+2

[0118] [Formula 3]

[0119] In Equation 3, x, a, b, and z can satisfy the following conditions: 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.4, -0.5 ≤ z ≤ 0.1. As mentioned above, M includes Co, Mn, and / or Al.

[0120] The chemical structure represented by Formula 3 indicates the bonding relationships between lithium (Li), nickel (Ni), oxygen (O), and metal (M) elements contained in the layered or crystalline structure of the cathode active material, but does not exclude the inclusion of additional elements. For example, M may contain Co and / or Mn, where Co and / or Mn together with Ni provide the main active elements of the cathode active material, but may cover the introduction of additional elements, such as those described below.

[0121] In one embodiment, the positive electrode active material may further comprise one or more auxiliary elements added to the primary active element to enhance its chemical stability or layered / crystal structure. The auxiliary elements may be incorporated into the layered / crystal structure together with the primary active element to form bonds. It should be understood that the auxiliary elements are included within the chemical structure range represented by Formula 3. Suitable auxiliary elements include, for example, one or more of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. In some embodiments, the inclusion of one or more auxiliary elements may function as auxiliary active elements, which, together with Co and / or Mn, contribute to the capacity / output activity of the positive electrode active material. In one embodiment, aluminum (Al) is included as an auxiliary element / auxiliary active element.

[0122] For example, the positive electrode active material or lithium nickel metal oxide may contain a layered structure or a crystal structure represented by the following formula 3-1.

[0123] Li x Ni a M1 b1 M2 b2 O 2+z

[0124] [Equation 3-1]

[0125] In Equation 3-1, M1 contains Co, Mn, and / or Al. M2 contains one or more of the above auxiliary elements. In Equation 3-1, x, a, b1, b2, and z can satisfy the following conditions: 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b1 + b2 ≤ 0.4, -0.5 ≤ z ≤ 0.1.

[0126] In some embodiments, the positive electrode active material may further comprise coating elements or doping elements. For example, elements substantially the same as or similar to the auxiliary elements described above may be used as coating elements or doping elements, either alone or in combination of two or more of them. The coating elements or doping elements may be present on the surface of the lithium nickel metal oxide particles, or may penetrate the surface of the lithium nickel metal composite oxide particles and bind to the bonding structure represented by Formula 2 or Formula 3-1 above.

[0127] In some embodiments, the use of a high-nickel-content (high-Ni) composition in the positive electrode active material is associated with improved output and capacity of the lithium secondary battery. Therefore, in one embodiment, the positive electrode active material comprises nickel-cobalt-manganese (NCM)-based lithium oxide to increase the nickel content in the positive electrode active material, thereby generating a secondary battery with a high-capacity positive electrode and a high-capacity lithium secondary battery.

[0128] However, those skilled in the art will recognize that with increasing Ni content, the long-term storage stability and cycle life stability of the cathode or secondary battery may relatively decrease, and side reactions with the electrolyte may also increase. However, these detrimental effects of using high-Ni cathode active materials can be mitigated by including Co, and the use of Mn can improve cycle life stability and capacity retention characteristics while maintaining the desired conductivity of the cathode active material.

[0129] In some embodiments, the NCM-based metal oxide may contain a molar fraction of Ni of about 0.6 or higher, about 0.7 or higher, or about 0.8 or higher (e.g., the molar fraction of nickel based on the total moles of nickel, cobalt, and manganese). In some embodiments, the Ni content in the NCM-based oxide is about 0.8 to about 0.95, about 0.82 to about 0.95, about 0.83 to about 0.95, about 0.84 to about 0.95, about 0.85 to about 0.95, or about 0.88 to about 0.95.

[0130] In some embodiments, the positive electrode active materials disclosed herein for secondary batteries include lithium cobalt oxide-based active materials, lithium manganese oxide-based active materials, lithium nickel oxide-based active materials, or lithium iron phosphate (LFP)-based active materials (e.g., LiFePO4).

[0131] In some embodiments, the positive electrode active material comprises, for example, a manganese-rich (Mn) active material having a chemical structure or crystal structure represented by Formula 4, a lithium-rich layered oxide (LLO) / over lithiated oxide (OLO) based active material, or a low cobalt (Co) active material.

[0132] p[Li2MnO3](1-p)[Li q JO2]

[0133] [Formula 4]

[0134] In Equation 4, p and q can satisfy the following conditions: 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J contains at least one element selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg and B.

[0135] In other embodiments, the positive electrode active material is a sodium-based or potassium-based active material. The sodium-based active material may comprise a layered or crystalline structure, wherein the Li in Formulas 3, 3-1, and / or 4 above is replaced by Na and / or K.

[0136] In other embodiments, the positive electrode active material is a calcium-based active material. The calcium-based active material may include, for example, calcium cobalt active materials and / or calcium phosphate active materials.

[0137] Positive electrode active materials can be prepared by any method known in the art. For example, a positive electrode slurry can be prepared by mixing the positive electrode active material in a solvent. Referring again... Figure 3 The positive electrode current collector 235 can be coated with a positive electrode slurry, then dried and rolled to prepare the positive electrode active material layer 230. The coating process can be carried out using methods such as gravure coating, slot coating, simultaneous multilayer coating, embossing, blade coating, dip coating, rod coating, or casting, but is not limited to these. The positive electrode active material layer 230 may further include a binder, and optionally may further include an electrolyte, conductive material, thickener, etc.

[0138] The solvent used to prepare the positive electrode active material layer 230 may include, for example, NMP, dimethylformamide (DMF), dimethylacetamide (DMA), N,N-dimethylaminopropylamine (DMAPA), ethylene oxide (EO), THF, etc.

[0139] The electrolyte contained in the positive electrode active material layer 230 can be any electrolyte described herein. In one embodiment, the positive electrode active material includes an electrolyte comprising an inorganic electrolyte as described herein. In one embodiment, the secondary battery is an all-solid-state battery comprising an electrolyte or an inorganic electrolyte as described herein.

[0140] The binder may include PVDF, poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethyl methacrylate, nitrile butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, the PVDF-based binder is used as the positive electrode binder.

[0141] The positive electrode active material layer 230 may contain conductive materials to enhance its conductivity and / or the mobility of lithium ions or electrons. For example, the conductive materials may include one or more carbon-based conductive materials, such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fibers (VGCF), carbon fibers, and / or metal-based conductive materials, such as perovskite materials (e.g., tin, tin oxide, titanium oxide, LaSrCoO3, or LaSrMnO3), but are not limited thereto.

[0142] In some embodiments, the positive electrode active material layer 230 further comprises a thickener and / or a dispersant. In one embodiment, the positive electrode active material layer 230 comprises a thickener, such as carboxymethyl cellulose (CMC).

[0143] Still refer to Figure 3 The negative electrode 260 may include a negative electrode current collector 255 and a negative electrode active material layer 250 disposed on at least one surface of the negative electrode current collector 255. The negative electrode current collector 255 may include, for example, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, etc. The thickness of the negative electrode current collector may be, for example, from about 10 μm to about 50 μm, but its thickness is not limited thereto.

[0144] The negative electrode active material layer 250 may contain a negative electrode active material, which may be a material capable of inserting and de-intercalating lithium ions. For example, the negative electrode active material may contain one or more crystalline carbon-based materials, such as crystalline carbon, amorphous carbon, carbon composite materials or carbon fibers; lithium metal; lithium alloys; silicon-containing (Si) materials, tin-containing (Sn) materials, etc.

[0145] Examples of amorphous carbon that can be used in anode active materials include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch-based carbon fiber (MPCF). Examples of crystalline carbon that can be used in anode active materials include graphite-based carbon, such as natural graphite, artificial graphite, graphite coke, graphite MCMB, and graphite MPCF.

[0146] When used in negative electrode active materials, lithium metal may comprise pure lithium metal or lithium metal with a protective layer formed thereon, which may be particularly useful for suppressing dendrite growth. In one embodiment, a lithium-containing metal layer deposited or coated on the negative electrode current collector 255 may be used as the negative electrode active material layer 250. In one embodiment, a lithium thin film layer may be used as the negative electrode active material layer 250.

[0147] When used in negative electrode active materials, lithium alloys may include, for example, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc.

[0148] When used in negative electrode active materials, silicon-containing materials can provide superior capacity characteristics. Silicon-containing materials may include Si, SiO₂, etc. x (where 0 < x < 2), metal-doped SiO x (where 0 < x < 2), silicon-carbon composite materials, etc. Metal-doped SiO x The metals in it may include lithium and / or magnesium.

[0149] For example, a negative electrode slurry can be prepared by mixing the negative electrode active material in a solvent. The negative electrode slurry can be coated / deposited onto a negative electrode current collector, then dried and rolled to prepare a negative electrode active material layer 250. The coating process can be performed using essentially the same method as for preparing the positive electrode active material layer 230. The negative electrode active material layer 250 may further include a binder, and optionally may further include an electrolyte, a conductive agent, a thickener, etc.

[0150] In some implementations, the negative electrode 260 may comprise a layer of negative electrode active material in the form of lithium metal formed by a deposition / coating process.

[0151] Solvents used for the negative electrode active material layer may include, for example, water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, etc.

[0152] In one embodiment, the electrolyte contained in the negative electrode active material layer 250 may be the electrolyte used in the secondary battery described above. In another embodiment, the electrolyte contained in the negative electrode active material layer 250 may be the inorganic electrolyte described above. For example, the secondary battery may be provided as an all-solid-state battery containing the electrolyte described above or an inorganic electrolyte.

[0153] The aforementioned materials that can be used as binders, conductive materials, and thickeners in the preparation of positive electrodes can also be used.

[0154] In some implementations, SBR-based binders, carboxymethyl cellulose, polyacrylic acid binders, and poly(3,4-ethylenedioxythiophene, PEDOT) binders can be used as negative electrode binders.

[0155] Still refer to Figure 3 Electrolyte layer 210 contains an electrolyte, such as any electrolyte disclosed herein (e.g., regarding...). Figure 1 The electrolyte 100 is described herein. The electrolyte layer 210 may contain the flame-retardant compound described herein. For example, the electrolyte layer 210 may be a membrane containing an electrolyte. In such embodiments, the membrane may be formed by impregnating the membrane with the first mixed solution described herein and curing the first mixed solution to polymerize or copolymerize the electrolyte monomer therein, as described herein.

[0156] like Figure 3 As shown, electrolyte layer 210 may be located between positive electrode 240 and negative electrode 260. In some embodiments, electrolyte layer 210 is a gel-polymer electrolyte layer 210 containing the electrolyte disclosed herein.

[0157] Electrode unit 200 includes a positive electrode 240, a negative electrode 260, and an electrolyte layer 210. Multiple electrode units 200 can be stacked to form an electrode assembly. The electrode assembly can be formed by, for example, winding, stacking, or folding the units. The electrode assembly can be disposed inside a housing. For example, a pouch-type housing, a prismatic housing, a cylindrical housing, or a button-type housing can be used as the housing of the electrode assembly.

[0158] In some implementations, electrode tabs (positive electrode tab and negative electrode tab), Figure 3 The electrode tabs (not shown) can protrude from the positive current collector 235 and the negative current collector 255 respectively, and can extend to one side of the housing in which the electrode assembly is disposed. The electrode tabs can be fused to one side of the housing and connected to electrode leads (positive lead and negative lead) that extend or are exposed outside the housing.

[0159] The embodiments of this disclosure will be further described below with reference to specific experimental examples. However, the embodiments and comparative examples included in the following experimental examples are only for illustrating this disclosure, and those skilled in the art will clearly understand that various modifications and variations can be made within the scope and spirit of this disclosure. All such modifications and variations should be included within the scope of this disclosure.

[0160] Example

[0161] Preparation Example 1: Preparation of Electrolyte Monomers

[0162] (1) Preparation of electrolyte monomers according to formula 1-1

[0163] A mixed solution was prepared by adding 100 ml of THF, 10 g (34.00 mmol) of 1H,1H,8H,8H-perfluoro-3,6-dioxaoctane-1,8-diol, and 4.13 g (40.80 mmol) of triethylamine to a reactor.

[0164] After cooling the reactor to 0°C, 2.8 g (30.95 mmol) of acryloyl chloride dissolved in 15 ml THF was added to the mixed solution within 1 hour.

[0165] Subsequently, the mixture was stirred and filtered at room temperature (25°C) for 18 hours, washed once each with 0.1N HCl aqueous solution, NaHCO3 aqueous solution and pure water (H2O), and then dried under reduced pressure to remove the solvent, thereby obtaining a concentrated solution.

[0166] The concentrate was purified by column chromatography using hexane and ethyl acetate to obtain 3.5 g of intermediate.

[0167] The obtained intermediate was dissolved in 100 mL of dichloromethane, and then 2.55 g (25.2 mmol) of triethylamine and 0.98 g (5.03 mmol) of dichlorophenylphosphine oxide were added sequentially. The reaction mixture was stirred at room temperature (25 °C) for 24 hours, and then washed once each with 0.1 N HCl aqueous solution, NaHCO3 aqueous solution, and pure water (H2O).

[0168] The mixture was then purified by column chromatography with hexane and ethyl acetate to give 2.67 g (yield: 19%) of electrolyte monomer.

[0169] The resulting electrolyte monomer is the compound represented by Formula 1-1 above. 1 1H-NMR chemical shifts (500MHz, CDCl3), δ: 7.83–7.86 (m, 2H), 7.63–7.67 (m, 1H), 7.53–7.57 (m, 2H), 6.51–6.54 (d, 2H), 6.16–6.21 (q, 2H), 5.97–5.99 (d, 2H), 4.49–4.59 (t, 4H), 4.37–4.47 (m, 4H)).

[0170] (2) Preparation of electrolyte monomers according to formula 1-2

[0171] A mixed solution was prepared by adding 100 ml of dichloromethane, 7.82 g (67.31 mmol) of 2-hydroxyethyl acrylate and 7.49 g (74.03 mmol) of triethylamine to a reactor.

[0172] After cooling the reactor to 0°C, 7.1 g (33.65 mmol) of phenyl dichlorophosphate was added to the mixed solution over 30 minutes.

[0173] Subsequently, the mixture was stirred at room temperature (25°C) for 21 hours, washed once each with 0.1N HCl aqueous solution, NaHCO3 aqueous solution and pure water (H2O), and then dried under reduced pressure to remove the solvent, thereby obtaining a concentrated solution.

[0174] The concentrate was purified by column chromatography using hexane and ethyl acetate to obtain 8.31 g (yield: 66.7%) of electrolyte monomer.

[0175] The resulting electrolyte monomer is a compound represented by formula 1-2 ( 1 1H-NMR chemical shift (500MHz, chloroform-d), δ: 7.31-7.38 (m, 2H), 7.15-7.22 (m, 3H), 6.41-6.44 (m, 2H), 6.08-6.13 (m, 2H), 5.84-5.87 (m, 2H), 4.37-4.39 (m, 8H)).

[0176] (3) Preparation of electrolyte monomers of formula 1-3

[0177] A mixed solution was prepared by adding 100 ml THF, 10 g (61.70 mmol) tetrafluoro-1,4-butanediol and 7.49 g (74.04 mmol) triethylamine to a reactor.

[0178] After cooling the reactor to 0°C, 5.08 g (56.15 mmol) of acryloyl chloride was added to the mixed solution over 1 hour. The reaction mixture was stirred at room temperature (25°C) and filtered for 18 hours to obtain a filtrate. Then, THF was removed under reduced pressure to obtain a preliminary intermediate.

[0179] Subsequently, the preliminary intermediate was dissolved in dichloromethane and washed once each with 0.1N HCl aqueous solution, NaHCO3 aqueous solution and pure water (H2O). It was then purified by column chromatography with hexane and ethyl acetate to obtain 4.47 g (yield: 36.9%) of the intermediate.

[0180] The obtained intermediate was dissolved in 50 mL of dichloromethane, and then 2.16 g (21.34 mmol) of triethylamine and 0.99 g (6.47 mmol) of phosphorus oxychloride (POCl3) were added sequentially. The reaction mixture was stirred at 0 °C for 24 hours, washed once each with 0.1 N HCl aqueous solution, NaHCO3 aqueous solution and pure water (H2O), and dried under reduced pressure.

[0181] The product was then purified by column chromatography with hexane and ethyl acetate to give 3.12 g (yield: 25.8%) of electrolyte monomer.

[0182] The resulting electrolyte monomer is a compound represented by formulas 1-3 above. 1 1H-NMR chemical shift (500MHz, CDCl3), δ: 6.51-6.55 (m, 3H), 6.17-6.23 (m, 3H), 5.97-6.00 (m, 3H), 4.63-4.68 (q, 6H), 4.52-4.59 (m, 6H)).

[0183] Preparation Example 2: Preparation of the First Mixed Solution

[0184] Example 1: A first mixed solution was prepared by mixing 5 wt% of the compound shown in Formula 1-1 above (as the electrolyte monomer) and 5 wt% of fluorinated ethylene carbonate (FEC, as an additive) with a 1.0 M LiPF6 solution (a mixed solvent of EC / EMC in a volume ratio of 3:7, as the lithium salt). Other first mixed solutions were prepared according to Table 1 below.

[0185] Table 1

[0186]

[0187]

[0188] The specific components described in Table 1 are as follows:

[0189] A1: The compound shown in Formula 1-1;

[0190] A2: The compound shown in Formula 1-2;

[0191] A3: The compounds shown in Formulas 1-3; and

[0192] B1: Trimethylolpropane ethoxylated triacrylate.

[0193] Preparation Example 3: Manufacturing of Lithium Secondary Batteries

[0194] LiNi will be used as the positive electrode active material 0.6 Co0.2 Mn 0.2 O2, PVDF as a binder, and carbon black as a conductive material are mixed in a weight ratio of 90:5:5 to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated onto aluminum foil, dried, and rolled to manufacture the positive electrode.

[0195] A negative electrode slurry was prepared by mixing natural graphite (as the negative electrode active material), SBR / CMC (as a binder), and carbon black (as a conductive material) in a weight ratio of 96:3:1. The negative electrode slurry was then uniformly coated onto a copper (Cu) foil, dried, and rolled to manufacture the negative electrode.

[0196] Polyethylene (PE) is prepared as a separator. The positive and negative electrodes are placed facing each other with the separator between them, and the tabs of the positive and negative electrodes are welded on respectively.

[0197] The welded positive / separator / negative electrode assembly is placed in a bag, and then three sides of the bag are sealed, leaving one side open for injecting a first mixed solution as the electrolyte for the secondary battery. At this point, the portion with the tabs is contained within the sealed portion. After injecting the first mixed solution through the remaining open side, this open side is also sealed, allowing the assembly to be immersed in the first mixed solution for 12 hours or longer. Subsequently, the assembly is heat-cured in an oven at 70°C for 1 hour to manufacture the secondary battery.

[0198] Comparative Example 1

[0199] As a comparative example, LiNi was used as the positive electrode active material. 0.6 Co 0.2 Mn 0.2 O2, PVDF as a binder, and carbon black as a conductive material are mixed in a weight ratio of 90:5:5 to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated onto aluminum foil, dried, and rolled to manufacture the positive electrode.

[0200] A negative electrode slurry was prepared by mixing natural graphite (as the negative electrode active material), SBR / CMC (as the binder), and carbon black (as the conductive material) in a weight ratio of 96:3:1. The negative electrode slurry was then uniformly coated onto a 10 μm thick Cu foil, followed by drying and rolling to manufacture the negative electrode.

[0201] Polyethylene (PE) is prepared as a separator. The positive and negative electrodes are placed facing each other with the separator between them, and the tabs of the positive and negative electrodes are welded on respectively.

[0202] The welded positive / separator / negative electrode assembly is placed in a bag, and then three sides of the bag (including those with tabs) are sealed, leaving one side for electrolyte injection. An electrolyte solution is prepared by adding 5 wt% FEC to a 1.0 M LiPF6 solution (a 3:7 volume ratio EC / EMC mixed solvent). After injecting the electrolyte through the remaining side, that side is also sealed, allowing the assembly to soak for 12 hours or longer to fabricate a secondary battery.

[0203] Comparative Examples 2 and 3 were manufactured in the same manner as Example 1, except that the type of electrolyte monomer was changed as shown in Table 1 when preparing the electrolyte monomer.

[0204] Experimental Example 1: Electrolyte Assessment

[0205] (1) Self-extinguishing performance assessment

[0206] 1) Examples 1 to 8 and Comparative Examples 2 and 3

[0207] Glass fibers were cut into 16 μm diameter pieces and dried at 120 °C to prepare dried glass fibers. The mass (g) of the dried glass fibers was then measured.

[0208] The gasket and dried glass fiber were placed sequentially at the bottom of the coin cell, followed by the injection of 0.5 mL of the first mixed solution prepared according to the above-described examples and comparative examples (Comparative Examples 2 and 3). Subsequently, the spacer and cap were placed sequentially to assemble the coin cell.

[0209] Dry glass fibers were placed and impregnated with the first mixed solution, then cured at 70°C for 1 hour. Subsequently, the coin battery was disassembled to prepare a sample (the cured sample of dry glass fibers impregnated with the first mixed solution), and the mass (g) of the sample was measured.

[0210] After igniting the sample, measure the time required for the flame to extinguish (extinguishing time).

[0211] The self-extinguishing time is calculated according to the following formula 1.

[0212] [Formula 1]

[0213]

[0214] 2) Comparative Example 1

[0215] Glass fibers were cut into 16 μm diameter pieces and dried at 120°C to prepare dried glass fibers.

[0216] Place 3 mL of the electrolyte according to Comparative Example 1 above into a sealed container and measure the mass (g) of the electrolyte.

[0217] Next, the dried glass fiber was placed in a sealed container and impregnated with electrolyte to prepare a sample. The sample was then removed, and the mass (g) of the unimpregnated residual electrolyte was measured.

[0218] After igniting the sample, measure the time required for the flame to extinguish (extinguishing time).

[0219] The self-extinguishing time is calculated according to the following formula 2.

[0220] [Formula 2]

[0221]

[0222] The calculation results of the self-extinguishing time are shown in Table 2 below.

[0223] Table 2

[0224]

[0225]

[0226] Referring to Table 2, in the examples where compounds of formulas 1-1 to 1-3 are used as electrolyte monomers, the self-extinguishing time is 95 s / g or less.

[0227] In Comparative Example 1, which did not use electrolyte monomers, the self-extinguishing time exceeded 125 s / g.

[0228] In Comparative Examples 2 and 3, which used compounds other than those shown in Formulas 1-1 to 1-3 as electrolyte monomers, the self-extinguishing time exceeded 95 s / g.

[0229] Experimental Example 2: Evaluation of Lithium Secondary Batteries

[0230] (1) Determination of initial capacity

[0231] The lithium secondary batteries of the above embodiments and comparative examples were charged in a chamber at 25°C (CC-CV 0.1C 4.3V 0.005C CUT-OFF), and then the initial charge capacity was measured. Then they were discharged (CC 0.1V 3.0V CUT-OFF), and then the initial discharge capacity was measured.

[0232] The measured initial charge capacity and initial discharge capacity are shown in Table 3 below.

[0233] (2) Assessment of cycle life retention

[0234] The lithium secondary batteries of the above embodiments and comparative examples were subjected to 50 cycles of repeated charging (CC / CV 0.5C 4.3V 0.05CC CUT-OFF) and discharging (CC 0.5C 2.7V CUT-OFF) at 25°C. Then, the cycle life retention was evaluated by dividing the discharge capacity at the 50th cycle by the discharge capacity at the 1st cycle.

[0235] The cycle life retention rates obtained from the assessment are shown in Table 3 below.

[0236] Table 3

[0237]

[0238] Referring to Table 3, in the examples using lithium secondary batteries comprising an electrolyte (the electrolyte comprising a polymer or copolymer of at least one electrolyte monomer selected from the group consisting of compounds represented by formulas 1-1 to 1-3), the cycle life retention exceeds 97.5%.

[0239] In Example 7, where the electrolyte monomer content was reduced, the initial capacity and cycle life retention were slightly lower.

[0240] In Example 8, where the electrolyte monomer content was increased, the initial capacity and cycle life retention were slightly reduced.

[0241] In comparative examples using electrolytes containing polymers or copolymers of monomers other than those shown in Formulas 1-1 to 1-3, or in comparative examples using electrolyte solutions without electrolyte monomers, cycle life retention was reduced.

Claims

1. A monomer for use in electrolytes, characterized in that, It is represented by the following equation 1: in: R1 is a substituted or unsubstituted C6-C12 aromatic hydrocarbon group, or *-R4-R5; R2 and R3 are each independently a substituted or unsubstituted C1-C6 alkylene group, or a substituted or unsubstituted C1-C7 alkylene group; R4 is a C3-C12 alkylene group in which at least one hydrogen atom is replaced by a fluorine atom; R5 is an aggregateable functional group; * indicates a bond to an adjacent oxygen atom; R6 and R7 are each independently hydrogen or C1-C5 alkyl; m and p are each independently 0-10; and n is 0 or 1.

2. The monomer for electrolytes according to claim 1, wherein, R1 is a substituted or unsubstituted C6-C10 aromatic hydrocarbon group, or *-R4-R5, wherein R5 is a (meth)acrylate group.

3. The monomer for electrolytes according to claim 2, wherein, R1 is a phenyl group, or *-R4-R5, where R4 is a C3-C6 alkylene group in which at least one hydrogen atom is replaced by a fluorine atom.

4. The monomer for electrolyte according to claim 1, wherein, R2 and R3 are each independently an unsubstituted or fluorinated C1-C3 alkylene group, or a fluorinated C1-C5 oxyalkylene group.

5. The monomer for an electrolyte according to claim 1, wherein: R1 is a substituted or unsubstituted C6-C10 aryl group, or *-R4-R5, wherein R5 is a (meth)acrylate group; and R2 and R3 are each independently an unsubstituted or fluorinated C1-C3 alkylene group, or a fluorinated C1-C5 oxyalkylene group.

6. The monomer for an electrolyte according to claim 5, wherein, n is 1.

7. The monomer for electrolytes according to claim 1, wherein, The monomer is represented by one or more of Formulas 1-1, 1-2 and 1-3:

8. An electrolyte, characterized in that, include: Flame retardant compounds comprising polymers of one or more monomers according to claim 1; as well as Lithium salts.

9. The electrolyte according to claim 8, wherein, The flame retardant compound comprises a polymer product of one or more monomers independently represented by formulas 1-1 to 1-3:

10. The electrolyte according to claim 8, wherein, The electrolyte also includes a porous composite electrolyte, which comprises organic polymers and inorganic electrolytes.

11. The electrolyte according to claim 10, wherein, The inorganic electrolyte includes oxide-based solid electrolytes.

12. The electrolyte according to claim 8, wherein, Based on the total weight of the electrolyte, the electrolyte comprises 1% to 30% by weight of the flame retardant compound.

13. The electrolyte according to claim 8, wherein, Based on the total weight of the electrolyte, the electrolyte comprises 5% to 20% by weight of the flame retardant compound.

14. A secondary battery, characterized in that, include: positive electrode; The negative electrode is positioned opposite the positive electrode; as well as An electrolyte layer is disposed between the positive electrode and the negative electrode, and includes the electrolyte according to claim 8.

15. The secondary battery according to claim 14, wherein the secondary battery is a lithium secondary battery.

16. A method for preparing an electrolyte, characterized in that, include: Prepare a first mixed solution comprising the monomer for electrolyte and the electrolyte solution according to claim 1; as well as The first mixed solution is solidified.

17. The method for preparing an electrolyte according to claim 16, further comprising contacting the first mixed solution with a porous membrane, wherein the curing occurs during the contact.

18. The method for preparing an electrolyte according to claim 17, wherein the porous membrane comprises an organic polymer, and the first mixed solution further comprises an inorganic electrolyte.

19. The method for preparing an electrolyte according to claim 16, wherein, Based on the total weight of the first mixed solution, the first mixed solution comprises 1% to 30% by weight of the monomer.

20. The method for preparing an electrolyte according to claim 16, wherein: The monomer includes thermally reactive functional groups, the first mixed solution further includes a thermal initiator, and the curing includes heat treatment of the first mixed solution, and / or The monomer includes photoreactive functional groups, the first mixed solution further includes a photoinitiator, and the curing includes irradiating the first mixed solution with light.

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