Cell for electrolyte, electrolyte for secondary battery comprising same, method for preparing same, and lithium secondary battery comprising 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 layer, and the electrolyte layer may include a polymer formed by polymerizing a compound represented by Formula 1. The electrolyte for a secondary battery has improved flame retardancy and ionic conductivity; the lithium secondary battery has improved stability and / or electrochemical properties.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0112222, filed on August 21, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to a monomer for use as an electrolyte, an electrolyte for use in a secondary battery comprising the monomer, a method for preparing the electrolyte, and a lithium secondary battery comprising the electrolyte. Background Technology

[0004] Rechargeable batteries are batteries that can be repeatedly charged and discharged. With the development of the information, communication, and display industries, rechargeable batteries have been widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops. Furthermore, battery packs including rechargeable batteries have recently been developed and applied as power sources for environmentally friendly vehicles such as hybrid vehicles.

[0005] Examples of rechargeable batteries include lithium-ion batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium-ion batteries have high operating voltage and high energy density per unit weight, which gives them advantages in terms of charging speed and weight reduction, thus enabling their development in this area.

[0006] Since commercially available lithium-ion batteries primarily use liquid electrolytes, they are susceptible to safety issues such as leakage, ignition, and explosion due to sudden environmental changes (including temperature fluctuations and external shocks). To address these issues, efforts are underway to solidify electrolytes to improve stability and increase energy density.

[0007] All-solid-state batteries can include solid electrolytes such as gel polymers, oxides, sulfides, or composite polymers. Therefore, they can improve stability against ignition and explosion caused by external shocks or fluctuations in the external environment.

[0008] However, in solid-state batteries, those including a portion of liquid electrolyte may pose a greater risk of ignition than all-solid-state batteries. Therefore, research is actively underway on flame-retardant additives that can be incorporated into the electrolyte to improve the ignition resistance of gel polymer electrolytes or composite polymer electrolytes. Summary of the Invention

[0009] One object of this disclosure is to provide an electrolyte monomer with improved flame retardancy.

[0010] Another object of this disclosure is to provide an electrolyte for secondary batteries that has improved flame retardancy and / or ionic conductivity.

[0011] Another object of this disclosure is to provide a method for preparing an electrolyte for secondary batteries, the electrolyte having improved flame retardancy and / or ionic conductivity.

[0012] Another object of this disclosure is to provide a lithium secondary battery with improved stability and / or electrochemical properties.

[0013] According to some non-limiting embodiments of this disclosure, the monomer for the electrolyte may comprise a compound represented by the following formula 1:

[0014] [Formula 1]

[0015]

[0016] In Formula 1, R1 and R2 can each be independently a substituted or unsubstituted C1 to C12 alkyl group or a substituted or unsubstituted C6 to C12 aromatic group, and R1 and R2 can be linked together to form a ring.

[0017] In Formula 1, R3 can be a substituted or unsubstituted C1 to C5 alkylene group.

[0018] In Formula 1, R4 can be hydrogen or C1 to C5 alkyl.

[0019] In Equation 1, m can be 1 to 5, and n can be 0 or 1.

[0020] In some non-limiting embodiments, R1 and R2 may each be independently a substituted or unsubstituted C1 to C10 alkyl or a substituted or unsubstituted C6 to C10 aromatic group, R1 and R2 may be linked to each other to form a ring, R3 may be a C2 alkylene group, R4 may be hydrogen or a C1 to C3 alkyl group, and m may be 1 to 3.

[0021] In some non-limiting implementations, m can be 1.

[0022] In some non-limiting embodiments, in Formula 1, n can be 1, R1 and R2 can each be independently substituted or unsubstituted C6 to C10 aryl or substituted or unsubstituted C1 to C7 alkyl, and R3 can be substituted or unsubstituted C1 to C3 alkylene.

[0023] In some non-limiting embodiments, in Formula 1, n can be 0, R1 and R2 can each be independently substituted or unsubstituted C1 to C7 alkyl groups, and R3 can be substituted or unsubstituted C1 to C3 alkylene groups.

[0024] In some non-limiting embodiments, in Formula 1, n can be 1, R1 and R2 can each be an unsubstituted C6 to C10 aryl or an unsubstituted C1 to C5 alkyl, and R3 can be an unsubstituted C2 alkylene.

[0025] In some non-limiting embodiments, in Formula 1, n can be 0, R1 and R2 can each be an unsubstituted C1 to C5 alkyl group, and R3 can be an unsubstituted C2 alkylene group.

[0026] In some non-limiting embodiments, the monomer for the electrolyte may include at least one selected from the group consisting of compounds represented by formulas 2 to 4:

[0027] [Equation 2]

[0028]

[0029] In Formula 2, R5 and R6 can each be hydrogen, substituted or unsubstituted C1 to C5 alkyl, or substituted or unsubstituted C6 to C10 aryl, and R7 can be hydrogen or C1 to C3 alkyl.

[0030] [Formula 3]

[0031]

[0032] In Formula 3, R8 and R9 can each be independently hydrogen, or substituted or unsubstituted C1 to C3 alkyl groups, and R 10 It can be hydrogen or C1 to C3 alkyl.

[0033] [Formula 4]

[0034]

[0035] In Equation 4, R 11 and R 12 Each can be independently hydrogen, or a substituted or unsubstituted C1 to C5 alkyl group, and R 13 It can be hydrogen or C1 to C3 alkyl.

[0036] In some non-limiting embodiments, the monomer for the electrolyte may include at least one selected from the group consisting of compounds represented by the following formulas 2-1, 2-2, 3-1 and 4-1.

[0037] [Equation 2-1]

[0038]

[0039] [Equation 2-2]

[0040]

[0041] [Equation 3-1]

[0042]

[0043] [Equation 4-1]

[0044]

[0045] In some non-limiting embodiments, the monomer for the electrolyte may include at least one of the compounds represented by Formula 3 above, the compounds represented by Formula 4 above, and the compound represented by Formula 2 above.

[0046] In some non-limiting embodiments, the monomer for the electrolyte may include compounds represented by Formula 2 above and compounds represented by Formula 4 above.

[0047] According to some non-limiting embodiments of this disclosure, the electrolyte for a secondary battery may include: a flame-retardant compound comprising a polymer formed by the polymerization of the monomers used for the electrolyte described above; and a lithium salt.

[0048] In some non-limiting embodiments, the content of the flame retardant compound can be from 3 wt% to 60 wt%, based on the total weight of the electrolyte used in the secondary battery.

[0049] According to some non-limiting embodiments of this disclosure, a lithium secondary battery may include: a positive electrode; a negative electrode disposed facing the positive electrode; and an electrolyte layer disposed between the positive and negative electrodes and containing the electrolyte described above for a secondary battery.

[0050] A method for preparing an electrolyte for a secondary battery according to some non-limiting embodiments of the present disclosure may include: preparing a first mixed solution comprising the monomer and electrolyte solution described above; and curing the first mixed solution.

[0051] In some non-limiting embodiments, the first mixed solution may also contain an organic polymer and an inorganic electrolyte.

[0052] In some non-limiting embodiments, the content of the monomer used for the electrolyte can be from 3 wt% to 60 wt%, based on the total weight of the first mixed solution.

[0053] In some non-limiting embodiments, the first mixed solution may also contain a thermal initiator, and the step of curing the first mixed solution may include heat treating the first mixed solution.

[0054] In some non-limiting embodiments, the first mixed solution may also contain a photoinitiator, and the step of curing the first mixed solution may include irradiating the first mixed solution with light.

[0055] According to some non-limiting embodiments of this disclosure, the monomer used for the electrolyte (“electrolyte monomer”) may have a self-extinguishing property. This can improve the ignition stability of the electrolyte containing the electrolyte monomer.

[0056] According to some non-limiting embodiments of this disclosure, electrolyte monomers can be included in the electrolyte for use in secondary batteries within a predetermined content range. This can simultaneously improve the stability and electrical properties of the electrolyte.

[0057] According to some non-limiting embodiments of this disclosure, the lithium secondary battery may include an electrolyte for use as a secondary battery. This can improve room temperature safety and high temperature safety, as well as ionic conductivity, thereby enhancing cycle life characteristics and electrical properties.

[0058] These and other features and characteristics of this disclosure, the methods of operation and function of related elements of the structure, and the economy of combination and manufacture of the components will become more apparent when considered with reference to the accompanying drawings, all of which form part of this specification, wherein the same reference numerals denote corresponding parts in the various drawings. However, it should be clearly understood that the drawings are for illustrative and descriptive purposes only and are not intended to be construed as limiting the scope of the disclosed subject matter. Attached Figure Description

[0059] The above and other objects, features and advantages of this disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0060] Figure 1 It is a schematic process flow diagram used to describe a method for preparing an electrolyte for a secondary battery according to an exemplary embodiment;

[0061] Figure 2 This is a schematic cross-sectional view showing an electrode cell according to an exemplary embodiment; and

[0062] Figure 3 This is a schematic diagram illustrating the structure of an electrolyte layer for a secondary battery according to an exemplary embodiment. Detailed Implementation

[0063] It should be understood that, unless expressly stated otherwise, this disclosure may take various alternative variations and sequences of steps. It should also be understood that the specific apparatus and processes shown in the accompanying drawings and described in the following specification are merely exemplary and non-limiting embodiments or aspects of the disclosed subject matter. Therefore, specific dimensions and other physical characteristics associated with the embodiments or aspects disclosed herein should not be considered as limitations.

[0064] Unless explicitly stated otherwise, aspects, components, elements, structures, actions, steps, functions, instructions, etc., used herein should not be construed as critical or essential. Unless otherwise stated, the singular forms of terms used herein may also include plural forms. As used herein, unless explicitly stated in the context, the singular forms “a,” “an,” and “described” include plural indicators.

[0065] For the purposes of this disclosure, unless otherwise stated, all figures used in this disclosure representing amounts of components, reaction conditions, dimensions, physical properties, etc., should be understood to be modified by the term "about" in all cases. Unless otherwise indicated, the numerical parameters set forth in this disclosure are approximate values ​​that may vary depending on the desired properties sought to be obtained by this disclosure.

[0066] The numerical range used in this specification includes all values ​​within the range, including the lower and upper limits, increments logically derived from the form and span of the defined range, all double-limited values, and all possible combinations of the upper and lower limits of numerical ranges defined in different forms. Unless otherwise defined in this disclosure, values ​​that may be outside the defined numerical range due to experimental error or rounding are also included within the defined numerical range.

[0067] Although the numerical ranges and parameters described in this disclosure are approximate, the values ​​described in the specific embodiments are reported as precisely as possible. However, any numerical value inherently contains a certain degree of error, which necessarily arises from the standard deviation found in their respective test measurements.

[0068] Furthermore, it should be understood that any numerical range referenced herein is intended to include all subranges contained therein. For example, the range “1 to 10” is intended to include any and all subranges between the minimum value 1 and the maximum value 10, that is, all subranges that begin with a minimum value equal to or greater than 1 and end with a maximum value equal to or less than 10, as well as all subranges between, for example, 1 to 6.3, or 5.5 to 10, or 2.7 to 6.1.

[0069] The term “comprise” as used in this disclosure is an open-ended description that has the same meaning as terms such as “include,” “set,” “contain,” or “have,” and does not exclude elements, materials, or processes not further listed.

[0070] According to some non-limiting 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 using the method are provided. Furthermore, a lithium secondary battery comprising an electrolyte layer containing an electrolyte for a secondary battery is also provided.

[0071] Non-limiting embodiments of this disclosure will be described in detail below. However, these are merely illustrative, and this disclosure is not limited to the specific embodiments described by way of example.

[0072] Unless otherwise defined herein, when a part of a layer, membrane, film, region, or plate is present “on” or “above” another part, it can include not only the case where the part is present “directly above” the other part, but also the case where other parts are present between them.

[0073] If there are isomers of the compound represented by the formula used herein, then the compound represented by the corresponding formula refers to the representative formula containing that isomer.

[0074] The term “substituted or unsubstituted Ca to Cb Y group” as used in this article refers to an unsubstituted Y group having a to b carbon atoms, excluding the number of carbon atoms of the substituents on the Y group.

[0075] As used herein, the term "aromatic group" refers to a group that exhibits overall aromaticity or contains an aromatic ring (such as a benzene ring) in its molecular structure. For example, an aromatic group may include substituted or unsubstituted aryl groups, substituted or unsubstituted arylalkyl groups, or substituted or unsubstituted alkylaryl groups.

[0076] 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.

[0077] As used herein, the terms “heteroalkyl,” “heterocyclic alkyl,” and “heteroaryl” can refer to at least one carbon atom of an alkyl, cycloalkyl, and aryl group being substituted with at least one atom selected from the group consisting of nitrogen, oxygen, and sulfur, respectively.

[0078] The term “unsubstituted” as used in this article can refer to a compound in which none of the hydrogen atoms have been substituted.

[0079] The term “unsubstituted alkylene” as used in this article may refer to a saturated hydrocarbon group in which the hydrogen atoms contained in the alkylene group are not replaced by other atoms or molecules.

[0080] The term “fluorine-substituted” as used in this article can refer to a compound in which at least one hydrogen atom is substituted by fluorine (F).

[0081] The term "flame retardancy" as used in this article refers to the property of preventing or inhibiting combustion, meaning that the sample burns upon contact with a flame (ignition source), but self-extinguishes once the flame is removed. Flame retardancy can be assessed based on the time it takes for the flame to extinguish after one second or longer following the removal of a torch that supplies heat to the sample. The shorter the time it takes for the flame to extinguish, the better the flame retardancy is assessed.

[0082] Specifically, the term "flame retardant compound" as used herein can be a compound that, when glass fibers cut to a diameter of 16 pi are impregnated with a flame retardant compound and cured as needed, and then ignited by a flame that provides a certain amount of heat with a blowtorch for 1 second or longer and the blowtorch is removed, exhibits an extinguishing time (s / g) of 72 s / g or less relative to the mass of the sample (e.g., 68 s / g or less).

[0083] As used in this disclosure, the term "solubility" refers to the mass (g) of an organic polymer that can be dissolved in 100g of a first solvent or a second solvent. For example, a solubility of 1g / 100g means that 1g of organic polymer dissolves in 100g of a first solvent or a second solvent.

[0084] According to some non-limiting embodiments, the electrolyte monomer may include a compound represented by Formula 1 below.

[0085] [Formula 1]

[0086]

[0087] The compound represented by Formula 1 above is a phosphorus-containing compound containing phosphate ester groups or phosphonate ester groups. Therefore, although not bound by a specific theory, the compound represented by Formula 1 above can thermally decompose during combustion upon ignition to generate polymetaphosphate. Furthermore, with the formation of polymetaphosphate, carbon compounds (e.g., charcoal) can be generated through dehydration, esterification, and dehydrogenation reactions of the polymetaphosphate. Polymetaphosphate can form a protective layer, and carbon compounds can form a carbon film; therefore, the compound represented by Formula 1 above can block oxygen and heat under high-temperature conditions (such as ignition and combustion). Therefore, the self-extinguishing properties of the following electrolytes containing polymers or copolymers of compounds represented by Formula 1 above can be very high.

[0088] Furthermore, free radicals (e.g., hydrogen radicals) generated by ignition with organic solvents, etc., can promote chain ignition in electrolytes. However, while not bound by any particular theory, phosphorus atoms contained in compounds represented by Formula 1 above can suppress chain ignition by removing free radicals (e.g., hydrogen radicals). Therefore, electrolytes containing compounds represented by Formula 1 above and their polymers or copolymers can exhibit high self-extinguishing properties and improved flame retardancy.

[0089] In some non-limiting embodiments, R1 and R2 may each be independently a substituted or unsubstituted C1 to C12 alkyl group or a substituted or unsubstituted C6 to C12 aromatic group.

[0090] In some non-limiting embodiments, R1 and R2 may each be independently substituted or unsubstituted C1 to C10, C1 to C8, C1 to C7, C1 to C5, C1 to C4, C1 to C3 or C1 to C2 alkyl groups.

[0091] In some non-limiting embodiments, R1 and R2 can be connected to each other to form a ring. For example, at least one carbon atom of R1 and at least one carbon atom of R2 can be connected to each other to form a ring.

[0092] In some non-limiting embodiments, R1 and R2 can each be independently a substituted or unsubstituted C6 to C10, C6 to C9, or C6 to C8 aryl group. For example, the aryl group can be phenyl, tolyl, xylyl, naphthyl, etc. Therefore, the heat resistance and structural stability of polymers or copolymers of compounds represented by Formula 1 above can be further improved.

[0093] In some non-limiting embodiments, R3 may be a substituted or unsubstituted C1 to C5 alkylene group. For example, R3 may be a C2 alkylene group (ethylene).

[0094] In some non-limiting embodiments, R4 may be hydrogen, or a substituted or unsubstituted C1 to C5 or C1 to C3 alkyl group.

[0095] In some non-limiting embodiments, m can be 1 to 5, or 1 to 3. For example, m can be 2 or 1. As m decreases, the phosphorus content per unit mass of the electrolyte comprising the polymer or copolymer of the compound represented by Formula 1 can be further increased. Therefore, the self-extinguishing property of the electrolyte can be further improved.

[0096] In some non-limiting implementations, n can be 0 or 1.

[0097] In some non-limiting embodiments, in the electrolyte monomer, R1 and R2 can each be independently a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C6 to C10 aromatic group; R1 and R2 can be linked to each other to form a ring; R3 can be a C2 alkylene group; R4 can be hydrogen or a C1 to C3 alkyl group; and m can be 1 to 3. Therefore, the increased phosphorus content relative to carbon further suppresses chain ignition of the electrolyte in the polymer or copolymer containing the electrolyte monomer and further improves flame retardancy.

[0098] In some non-limiting embodiments, m can be 1. In this case, because the phosphorus content of the electrolyte monomer is further increased, chain ignition of the electrolyte in the polymer or copolymer containing the electrolyte monomer can be further suppressed, and flame retardancy can be further improved.

[0099] In some non-limiting embodiments, when n in Formula 1 above is 1, R1 and R2 may each be independently substituted or unsubstituted C6 to C10 aryl or substituted or unsubstituted C1 to C7 alkyl; and R3 may be substituted or unsubstituted C1 to C3 alkylene.

[0100] In some non-limiting embodiments, when n in Formula 1 is 0, R1 and R2 can each be independently substituted or unsubstituted C1 to C7 alkyl groups; and R3 can be a substituted or unsubstituted C1 to C3 alkylene group. Therefore, the phosphorus content by weight of the monomer represented by Formula 1 above can be further increased. As a result, the self-extinguishing property of the electrolyte of the polymer or copolymer containing this monomer can be further improved.

[0101] In some non-limiting embodiments, when n in Formula 1 above is 1, R1 and R2 may each be an unsubstituted C6 to C10 aryl or an unsubstituted C1 to C5 alkyl; and R3 may be an unsubstituted C2 alkylene.

[0102] In some non-limiting embodiments, when n in Formula 1 is 0, R1 and R2 can each be independently unsubstituted C1 to C5 alkyl groups; and R3 can be an unsubstituted C2 alkylene group. Therefore, the phosphorus content by weight of the monomer represented by Formula 1 above can be further increased. Therefore, the self-extinguishing property of the electrolyte containing the polymer or copolymer of this monomer can be further improved.

[0103] In some non-limiting embodiments, the electrolyte monomer may include at least one selected from the group consisting of compounds represented by Formulas 2 to 4 below. For example, the compound represented by Formula 1 above may include at least one selected from the group consisting of compounds represented by Formulas 2 to 4 below.

[0104] [Equation 2]

[0105]

[0106] In Formula 2, R5 and R6 can each be hydrogen, substituted or unsubstituted C1 to C5 alkyl, or substituted or unsubstituted C6 to C10 aryl, and R7 can be hydrogen or C1 to C3 alkyl.

[0107] In some non-limiting embodiments, the compound represented by Formula 2 may include its equivalents. For example, in Formula 2, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 2, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0108] [Formula 3]

[0109]

[0110] In Formula 3, R8 and R9 can each be independently hydrogen, or substituted or unsubstituted C1 to C3 alkyl groups, and R 10 It can be hydrogen or C1 to C3 alkyl.

[0111] In some non-limiting embodiments, the compound represented by Formula 3 may include its equivalents. For example, in Formula 3, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 3, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0112] [Formula 4]

[0113]

[0114] In Equation 4, R 11 and R 12 Each can be independently hydrogen, or a substituted or unsubstituted C1 to C5 alkyl group, and R 13 It can be hydrogen or C1 to C3 alkyl.

[0115] In some non-limiting embodiments, the compound represented by Formula 4 may include its equivalents. For example, in Formula 4, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 4, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0116] The compounds represented by Formulas 2 to 4 have phosphate ester or phosphonate ester groups and exhibit a high content of non-shared electron pairs. Furthermore, the phosphorus-to-carbon ratio is very high. Therefore, electrolytes containing polymers or copolymers of these compounds can suppress chain ignition in the event of combustion.

[0117] In some non-limiting embodiments, the compound represented by Formula 2 may contain at least one of Formula 2-1 and Formula 2-2.

[0118] [Equation 2-1]

[0119]

[0120] The compound represented by Formula 2-1 contains a phosphate ester group and a phenyl group. Therefore, the ignition onset temperature of the compound represented by Formula 2-1 can be increased. Furthermore, the compound represented by Formula 2-1 exhibits a high phosphorus content per unit molecule by weight. Therefore, the chain ignition reaction of electrolytes in polymers or copolymers containing electrolyte monomers can be further suppressed, and self-extinguishing properties can be further improved.

[0121] In some non-limiting embodiments, the compound represented by Formula 2-1 may include its equivalents. For example, in Formula 2-1, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 2-1, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0122] [Equation 2-2]

[0123]

[0124] The compound represented by Formula 2-2 contains a phosphate ester group and has a small number of carbon atoms bonded to the phosphate ester group. Therefore, the relative phosphorus content by weight in the electrolyte monomer can be increased. As a result, the chain ignition reaction of the electrolyte in the polymer or copolymer containing the electrolyte monomer can be further suppressed, and the self-extinguishing property can be further improved.

[0125] In some non-limiting embodiments, the compound represented by Formula 2-2 may include its equivalents. For example, in Formula 2-2, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 2-2, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0126] In some non-limiting embodiments, the compound represented by Formula 3 may include the compound represented by Formula 3-1 below.

[0127] [Equation 3-1]

[0128]

[0129] The compound represented by Formula 3-1 contains a phosphate ester group and a heterocyclic alkyl group. When the compound represented by Formula 3-1 is ignited, the structure of the heterocyclic alkyl group may collapse, thereby forming a poly(methoxyphosphate) and a carbon compound. Furthermore, the compound represented by Formula 3-1 exhibits a high phosphorus content per unit molecule by weight. Therefore, the chain ignition reaction of electrolytes containing polymers or copolymers of the aforementioned electrolyte monomers can be further suppressed, and self-extinguishing properties can be further improved.

[0130] In some non-limiting embodiments, the compound represented by Formula 3-1 may include its equivalents. For example, in Formula 3-1, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 3-1, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0131] In some non-limiting embodiments, the compound represented by Formula 4 may include the compound represented by Formula 4-1 below.

[0132] [Equation 4-1]

[0133]

[0134] The compound represented by Formula 4-1 contains a phosphonate group and has a small number of carbon atoms bonded to the phosphonate group. Therefore, the relative phosphorus content by weight in the electrolyte monomer can be increased. Consequently, the chain ignition reaction of the electrolyte containing the electrolyte monomer in the polymer or copolymer can be further suppressed, and the self-extinguishing property can be further improved.

[0135] In some non-limiting embodiments, the compound represented by Formula 4-1 may include its equivalents. For example, in Formula 4-1, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 4-1, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0136] In some non-limiting embodiments, the compound represented by Formula 1 above may include at least one selected from the compounds represented by Formulas 2-1, 2-2, 3-1 and 4-1 above.

[0137] For example, a compound represented by Formula 1 above may include at least one of the compounds represented by Formula 2-1, Formula 2-2, Formula 3-1, and Formula 4-1. For example, two or more of the compounds represented by Formula 2-1, Formula 2-2, Formula 3-1, and Formula 4-1 may be used as electrolyte monomers. The polymer or copolymer of the electrolyte monomer may be a cross-linked polymer or a network polymer, and may have thermosetting properties. Therefore, the flame retardancy of the electrolyte comprising the polymer or copolymer of the electrolyte monomer can be further improved.

[0138] In some non-limiting embodiments, the electrolyte monomer may include at least one of the compounds represented by Formula 3, the compounds represented by Formula 4, and the compound represented by Formula 2. For example, a combination of the compound represented by Formula 3-1 and the compound represented by Formula 2-1, or a combination of the compound represented by Formula 4-1 and the compound represented by Formula 2-2, may be used as the electrolyte monomer. Therefore, the flame retardancy of the electrolyte in the polymer or copolymer containing the electrolyte monomer can be further improved.

[0139] In some non-limiting embodiments, compounds represented by Formula 2 and Formula 4 can be used as electrolyte monomers. For example, compounds represented by Formula 2-2 and Formula 4-1 can be used in combination. Therefore, the flame retardancy of electrolytes comprising polymers or copolymers containing electrolyte monomers can be further improved.

[0140] According to some non-limiting embodiments, the flame retardant compound may include polymers and / or copolymers of the electrolyte monomers described above. For example, side reactions between the flame retardant compound and the electrolyte, which will be described below, can be suppressed. Furthermore, the flame retardant compound may contain phosphorus-containing functional groups, thereby cutting off oxygen during combustion and preventing thermal runaway.

[0141] In some non-limiting embodiments, the flame retardant compound may be a polymer or copolymer of an electrolyte monomer containing thermally reactive and / or photoreactive functional groups. For example, the electrolyte monomer may contain acrylate groups. Therefore, the acrylate groups in the polymer or copolymer can be used as thermally reactive or photoreactive functional groups.

[0142] In some non-limiting embodiments, the flame retardant compound may include a polymer formed by polymerizing the compound represented by Formula 1. For example, the flame retardant compound may include a polymer or copolymer of the compound represented by Formula 1. For example, the polymer may be formed by polymerizing the (meth)acrylate group contained in the compound represented by Formula 1.

[0143] In some non-limiting embodiments, the flame retardant compound may include a compound represented by Formula 5. For example, the flame retardant compound may be a cross-linked polymer or a network polymer in which compounds represented by Formula 5 are linked as unit structures.

[0144] [Formula 5]

[0145]

[0146] In Equation 5, R1, R2, R3, R4, m, and n can be the same as those described in Equation 1 above, and * denotes a bonding site.

[0147] In some non-limiting embodiments, the compound represented by Formula 5 may include its equivalents. For example, in Formula 5, at least one hydrogen atom bonded to a carbon atom may be further substituted with a substituent within the equivalent range. For example, in Formula 5, at least one hydrogen atom bonded to a carbon atom may be further substituted with deuterium or an alkyl group having 1 to 5 carbon atoms.

[0148] According to some non-limiting embodiments, the electrolyte (hereinafter also referred to as "electrolyte") for a secondary battery may comprise a flame-retardant compound and a lithium salt. For example, the flame-retardant compound may comprise a polymer of the electrolyte monomers described above.

[0149] In some non-limiting embodiments, the flame retardant compound may comprise a copolymer of the aforementioned electrolyte monomer and other monomers. Other monomers may comprise acrylate groups, such as trimethylolpropane tri(meth)acrylate (TMPT(M)A).

[0150] Lithium salts, for example, can be Li + X - In some non-limiting embodiments, the anion (X-) of the lithium salt may include 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 - One or more of the following.

[0151] In some non-limiting embodiments, the electrolyte may also include a composite electrolyte comprising an organic polymer and an inorganic electrolyte.

[0152] In some non-limiting embodiments, the composite electrolyte may be in membrane form. In some non-limiting embodiments, the organic polymer and the inorganic electrolyte may form a composite membrane. For example, the organic polymer and the inorganic electrolyte may be physically bonded within the composite membrane.

[0153] Organic polymers can be ionically conductive polymers. For example, organic polymers can contain repeating units based on ethers, styrene, and fluorinated hydrocarbon groups, etc.

[0154] In some non-limiting embodiments, the organic polymer may include at least one selected from polyvinylidene fluoride (PVDF), polystyrene (PS), polyethersulfone (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 some non-limiting embodiments, the organic polymer may include at least one selected from polyvinylidene fluoride, polystyrene, polyethersulfone, and polyurethane. Therefore, the mobility of lithium ions within the composite electrolyte can be improved, thereby enhancing ionic conductivity.

[0155] In some non-limiting embodiments, the inorganic electrolyte may be an oxide-based solid electrolyte. For example, an oxide-based solid electrolyte may include an ion-conducting compound containing a metal or oxygen. For example, an oxide-based solid electrolyte may include: LLTO compounds, LLZO compounds, LLZTO compounds (such as Li...). 6.4 La3Zr 1.4 Ta 0.6 O 12 Li6La2CaTa2O 12 Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4)3(0≤x≤1,0≤y≤1), LiAlx Zr 2-x (PO4)3(0≤x≤1,0≤y≤1), LiTi x Zr 2-x (PO4)3 (0≤x≤1, 0≤y≤1), LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and metal oxides (such as Al2O3, ZnO2, Ce2O2, TiO2, ZrO2, HfO2, MnO2, MgO, WO2 and V2O5, etc.).

[0156] In one non-limiting embodiment, the inorganic electrolyte can be a lithium-containing oxide-based solid electrolyte. For example, lithium-containing oxide-based solid electrolytes may include lithium lanthanum titanium oxide (LLTO) compounds, lithium lanthanum zirconium oxide (LLZO) compounds (e.g., garnet-type LLZO compounds), lithium lanthanum zirconium tantalum oxide (LLZTO) compounds, sodium superionic conductor (NASICON) compounds, lithium aluminum titanium phosphate (LATP) compounds, perovskite compounds, etc. Therefore, the ionic conductivity and mechanical strength of the electrolyte can be improved, thereby suppressing lithium dendrite growth and enhancing high-temperature stability and cycle life characteristics.

[0157] In some non-limiting embodiments, the content of the flame retardant compound may be 3 wt% to 60 wt%, 3 wt% to 49 wt%, 3 wt% to 30 wt%, 5 wt% to 30 wt%, or 5 wt% to 25 wt%, based on the total weight of the electrolyte. Within the above ranges, the ionic conductivity and flame retardancy of the electrolyte can be further improved.

[0158] In some non-limiting embodiments, the content of the flame retardant compound may be 5 wt% to 20 wt%, 7 wt% to 20 wt%, or 10 wt% to 20 wt%, depending on the total weight of the electrolyte. Within the above ranges, the flame retardancy and ionic conductivity of the electrolyte can be further improved.

[0159] In some non-limiting embodiments, pores can be formed in the composite membrane. Therefore, flame retardant compounds can be located within the pores of the composite membrane. This can result in improved ionic conductivity and flame retardancy of the electrolyte, and reduced resistance.

[0160] Figure 1 This is a process flow diagram describing a method for preparing an electrolyte for a secondary battery according to some non-limiting embodiments. The following will refer to... Figure 1 A method for preparing the above-mentioned electrolyte for use in secondary batteries is described.

[0161] Reference Figure 1 A first mixed solution comprising the above-mentioned electrolyte monomer and electrolyte solution can be prepared (e.g., step S10).

[0162] In some non-limiting embodiments, the electrolyte monomer and electrolyte solution described above can be mixed to prepare a first mixed solution.

[0163] In some non-limiting embodiments, the first mixed solution may also contain an organic polymer and an inorganic electrolyte. For example, the first mixed solution may contain an electrolyte monomer, an electrolyte solution, an organic polymer, and an inorganic electrolyte.

[0164] In some non-limiting embodiments, the organic polymer and inorganic electrolyte can be mixed with the electrolyte monomer and electrolyte solution in the form of a composite electrolyte membrane.

[0165] Composite electrolyte membranes can be prepared by drying a second mixed solution containing an organic polymer, an inorganic electrolyte, a first solvent, and a second solvent.

[0166] In some non-limiting embodiments, the solubility of the organic polymer in the first solvent may be greater than its solubility in the second solvent. For example, the solubility of the organic polymer in the first solvent may be 1 g / 100 g or greater, 33 g / 100 g or greater, 10 g / 100 g or greater, 100 g / 100 g or greater, or from 100 g / 100 g to 1000 g / 100 g. For example, the solubility of the organic polymer in the second solvent may be less than 1 g / 100 g, less than 0.1 g / 100 g, or less than 0.01 g / 100 g.

[0167] In some non-limiting embodiments, the organic polymer in the first mixed solution may be soluble in the first solvent but may not be soluble in the second solvent.

[0168] For example, the organic polymer may be soluble in the first solvent. Therefore, the organic polymer can be dissolved in the first solvent.

[0169] For example, organic polymers may be insoluble in the second solvent. Therefore, organic polymers may be substantially insoluble in the second solvent.

[0170] In some non-limiting embodiments, the first solvent may be miscible with the second solvent. For example, the first solvent and the second solvent may be mixed or blended.

[0171] The organic polymer and inorganic electrolyte can be the aforementioned organic polymer and inorganic electrolyte.

[0172] The first solvent can be a solvent for dissolving organic polymers and can be miscible with the second solvent. The first solvent may include, for example, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), N-methyl-2-pyrrolidone (NMP), 1,3-dioxolane, and / or vinylene carbonate (VC). These can be used alone or in combination of two or more. In some non-limiting embodiments, the first solvent may be tetrahydrofuran.

[0173] The second solvent can be a solvent that does not dissolve the organic polymer and is miscible with the first solvent. The second solvent may include, for example, heptane, octane, nonane, decane, dodecane, and / or 2,2,4-trimethylpentane. These can be used alone or in combination of two or more. In some non-limiting embodiments, the second solvent may be octane.

[0174] Drying can be achieved by casting the first mixed solution onto a substrate (e.g., a glass substrate, a plastic substrate, etc.).

[0175] In some non-limiting embodiments, drying the first mixed solution to prepare the composite membrane may include removing the first solvent and the second solvent from the first mixed solution.

[0176] In some non-limiting embodiments, drying the second mixed solution may include removing the first solvent at a first temperature and removing the second solvent at a second temperature. For example, the first solvent in the second mixed solution may be dried, and then the second solvent may be dried to prepare a composite electrolyte membrane. The first and second drying may be performed continuously, or the second drying may be performed after a certain period of time following the first drying. Therefore, the first solvent may be dried first, and then the second solvent may be dried.

[0177] In some non-limiting embodiments, the content of the electrolyte monomer can be 3 wt% to 60 wt%, 3 wt% to 49 wt%, 3 wt% to 30 wt%, 5 wt% to 30 wt%, or 5 wt% to 25 wt%, based on the total weight of the first mixed solution. Within the above ranges, the ionic conductivity of the electrolyte can be improved, while the flame retardancy can be enhanced.

[0178] In one non-limiting embodiment, the content of the electrolyte monomer can be 5 wt% to 20 wt%, 7 wt% to 20 wt%, or 10 wt% to 20 wt%, based on the total weight of the first mixed solution. Within the above ranges, the ionic conductivity of the electrolyte can be improved, while the flame retardancy of the electrolyte can be further enhanced.

[0179] In some non-limiting embodiments, the electrolyte monomer may contain thermally reactive or photoreactive functional groups and phosphorus-containing functional groups.

[0180] In some non-limiting embodiments, the electrolyte solution may contain a thermal initiator and / or a photoinitiator to induce thermal curing and / or photocuring of the first mixed solution. In some non-limiting embodiments, the content of the thermal initiator and / or photoinitiator may be from 0.5 parts by weight (“wt parts”) to 2 parts by weight, based on 100 parts by weight of the first mixed solution contained in each electrolyte composition.

[0181] For example, thermal initiators may include azo compounds (e.g., 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), 2,2'-azobis(2-azobisobutyronitrile, AIBN), azobisdimethyl-valeronitrile (AMVN), dimethyl 2,2'-azobis(2-methylpropionic acid), 2,2'-azobis(2,4-dimethylvaleronitrile), etc.) or peroxides (e.g., benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, propylphenyl peroxide, and / or hydrogen peroxide, etc.).

[0182] For example, photoinitiators may include 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-trimethylphosphine oxide, and / or α-amino ketone, etc.

[0183] In some non-limiting embodiments, the electrolyte solution may contain the aforementioned lithium salt. Therefore, the ionic conductivity of the electrolyte used in secondary batteries can be improved.

[0184] In some non-limiting embodiments, the electrolyte solution may contain an organic solvent. For example, the organic solvent may include: carbonate organic solvents such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methylpropyl carbonate (MPC), dipropyl carbonate (DPC), and / or vinylene carbonate (VC); or other solvents such as dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, γ-butyrolactone, propylene sulfite, and / or tetrahydrofuran. These may be used alone or in combination of two or more.

[0185] In some non-limiting embodiments, the organic solvent may be a carbonate-based organic solvent. Therefore, the electrical and chemical stability of the electrolyte used in secondary batteries can be further improved.

[0186] In some non-limiting embodiments, the electrolyte solution may also contain one or more additives. Additives may include cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulfonyl lactone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and / or borate compounds, etc.

[0187] In some non-limiting embodiments, the cyclic carbonate compound may include vinylene carbonate and / or vinylethylene carbonate (VEC), etc.

[0188] In some non-limiting embodiments, the fluorinated cyclic carbonate compound may include fluoroethylene carbonate (FEC) and the like.

[0189] In some non-limiting embodiments, the sulfonyl compound may include 1,3-propanesulfonyl, 1,3-propenesulfonyl and / or 1,4-butanesulfonyl, etc.

[0190] In some non-limiting embodiments, the cyclic sulfate compound may include vinyl 1,2-sulfate and / or propylene 1,2-sulfate, etc.

[0191] In some non-limiting embodiments, the cyclic sulfite compound may include vinyl sulfite and / or butene sulfite, etc.

[0192] In some non-limiting embodiments, the phosphate compound may include lithium difluorobis(oxalate)phosphate and / or lithium difluorophosphate, etc.

[0193] In some non-limiting embodiments, the borate compound may include lithium bis(oxalate)borate, etc.

[0194] According to some non-limiting embodiments, the first mixed solution can be solidified (e.g., step S20). Therefore, an electrolyte for a secondary battery can be prepared.

[0195] In some non-limiting embodiments, the polymer or copolymer of the electrolyte monomer can be formed during the curing of the first mixed solution. Therefore, the electrolyte for a secondary battery can contain a flame-retardant compound comprising a polymer or copolymer of the electrolyte monomer.

[0196] In some non-limiting embodiments, the weight change (decrease or increase) that occurs during the curing of the first mixed solution, based on the total weight of the electrolyte monomers, can be 0.0001 wt%, or 0.00001 wt%, or less. Therefore, the content of the electrolyte monomers contained in the first mixed solution can be substantially the same as the content of the flame-retardant compound contained in the electrolyte.

[0197] In some non-limiting embodiments, the first mixed solution can be cured by heat treatment. Therefore, the electrolyte monomers contained in the first mixed solution can be polymerized or copolymerized to form a flame-retardant compound.

[0198] In some non-limiting embodiments, the heat treatment temperature may be 40°C to 160°C, 60°C to 160°C, 80°C to 160°C, 80°C to 140°C, or 80°C to 120°C. In some non-limiting embodiments, the heat treatment temperature may be increased from room temperature (e.g., 25°C) at a rate of 1°C / min to 10°C / min, 2°C / min to 10°C / min, or 3°C / min to 10°C / min.

[0199] In some non-limiting embodiments, the heat treatment time may be 5 minutes to 12 hours, 5 minutes to 6 hours, 10 minutes to 6 hours, or 10 minutes to 3 hours.

[0200] Within the aforementioned temperature and time range, the electrolyte monomers contained in the first mixed solution can be fully polymerized or copolymerized.

[0201] In some non-limiting embodiments, the first mixed solution can be cured by light irradiation. Therefore, the electrolyte monomers contained in the first mixed solution can be polymerized or copolymerized at relatively low temperatures. This prevents side reactions of the electrolyte, etc., caused by high-temperature heat treatment.

[0202] In some non-limiting embodiments, the light may have a wavelength of 250 nm to 400 nm.

[0203] In some non-limiting embodiments, the light can have 800 mW / cm². 2 Up to 1100mW / cm 2 The intensity.

[0204] In some non-limiting embodiments, the light exposure time can be 5 seconds to 10 minutes, 5 seconds to 5 minutes, or 5 seconds to 3 minutes.

[0205] Within the aforementioned wavelength and intensity range, the electrolyte monomers contained in the first mixed solution can be fully polymerized or copolymerized.

[0206] Figure 2 This is a schematic cross-sectional view showing an electrode unit according to some non-limiting embodiments.

[0207] A secondary battery according to some non-limiting embodiments may include electrode units. (See reference...) Figure 2 The electrode unit may include a positive electrode 240, a negative electrode 260 disposed facing the positive electrode 240, and an electrolyte layer 210 disposed between the positive electrode 240 and the negative electrode 260.

[0208] 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.

[0209] The positive electrode current collector 235 may include stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector 235 may also include aluminum or stainless steel having a surface treated with carbon, nickel, titanium, or silver. The positive electrode current collector 235 may have a thickness of, for example, from 10 μm to 50 μm, but is not limited thereto.

[0210] Positive electrode active materials can contain compounds that can reversibly insert and deintercalate lithium ions.

[0211] According to some non-limiting embodiments, the positive electrode active material may comprise a lithium nickel metal oxide. The lithium nickel metal oxide may also comprise at least one element selected from the group consisting of cobalt (Co), manganese (Mn), and aluminum (Al).

[0212] In some non-limiting embodiments, the positive electrode active material or lithium nickel metal oxide may comprise a layered structure or a crystal structure represented by the following formula 6.

[0213] [Formula 6]

[0214] Li x Ni a M b O 2+2

[0215] In Equation 6, x, a, b, and z can satisfy 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.4, and -0.5 ≤ z ≤ 0.1. As mentioned above, M can include Co, Mn, and / or Al.

[0216] The chemical structure represented by Formula 6 indicates the bonding relationships between elements contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can be provided together with Ni as the main active elements of the positive electrode active material. Here, it should be understood that Formula 6 is provided to express the bonding relationships between the main active elements, and Formula 6 is a formula that includes the introduction and substitution of additional elements.

[0217] In some non-limiting embodiments, the positive electrode active material may also contain auxiliary elements added to the main active element to enhance the chemical stability of the layered / crystal structure. The auxiliary elements may be mixed with the main active element into the layered / crystal structure to form bonds, and it should be understood that this also includes the chemical structures represented by Formula 6.

[0218] Auxiliary elements may include, for example, at least one 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. Auxiliary elements (such as Al) can be used as auxiliary active elements, which, together with Co or Mn, contribute to the capacity / output activity of the positive electrode active material.

[0219] For example, the positive electrode active material or lithium nickel metal oxide may include a layered structure or a crystal structure represented by Formula 6-1.

[0220] [Equation 6-1]

[0221] Li x Ni a M1 b1 M2 b2 O 2+z

[0222] In Equation 6-1, M1 may include Co, Mn and / or Al. M2 may include the aforementioned auxiliary elements. In Equation 6-1, x, a, b1, b2 and z may satisfy 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, and -0.5≤z≤0.1.

[0223] The positive electrode active material may also contain coating elements and / or doping elements. For example, elements that are substantially the same as or similar to the auxiliary elements described above may be used as coating elements and / or doping elements. For example, the aforementioned elements may be used alone or in combination of two or more of them as coating elements or doping elements.

[0224] The coating element and / or doping element 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, thereby being included in the bonding structure represented by Formula 6 or Formula 6-1 above.

[0225] The positive electrode active material can contain nickel-cobalt-manganese (NCM) based lithium oxide. In this case, NCM-based lithium oxide with increased nickel content can be used.

[0226] Ni can be provided as a transition metal related to the output and capacity of lithium secondary batteries. Therefore, by using a high-nickel content (High-Ni) composition in the positive electrode active material as described above, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0227] However, with increasing Ni content, the long-term storage stability and cycle life stability of the cathode or secondary battery can relatively decrease, and side reactions with the electrolyte can also increase. However, according to some non-limiting embodiments, cycle life stability and capacity retention characteristics can be improved by including Mn while maintaining conductivity through Co.

[0228] The Ni content in NCM-based lithium oxide (e.g., the mole fraction of nickel based on the total moles of nickel, cobalt, and manganese) can be 0.6 or higher, 0.7 or higher, or 0.8 or higher. In some non-limiting embodiments, the Ni content can be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0229] In some non-limiting embodiments, the positive electrode active material may also include active materials based on lithium cobalt oxide, active materials based on lithium manganese oxide, active materials based on lithium nickel oxide, and / or active materials based on lithium iron phosphate (LFP) (e.g., LiFePO4).

[0230] In some non-limiting embodiments, the positive electrode active material may include, for example, a manganese (Mn)-rich active material, a lithium (Li)-rich layered oxide (LLO) / over lithiated oxide (OLO)-based active material, and / or a low cobalt (Co) active material having a chemical structure or crystal structure represented by the following formula 7.

[0231] [Formula 7]

[0232] p[Li2MnO3]·(1-p)[Li q JO2]

[0233] In formula 7, p and q may satisfy 0 < p < 1, and 0.9 ≤ q ≤ 1.2, and J may include at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0234] In some non-limiting embodiments, the positive electrode active material may also be a sodium-based active material and / or a potassium-based active material. The sodium-based active material may include a layered structure or crystal structure in which Li in the above formula 6, formula 6-1, and / or formula 7 is replaced by Na and / or K.

[0235] In some non-limiting embodiments, the positive electrode active material may also be a calcium-based active material. The calcium-based active material may include, for example, a calcium-cobalt active material and / or a calcium-phosphate active material, etc.

[0236] For example, the positive electrode paste may be prepared by mixing the positive electrode active material in a solvent. The positive electrode paste may be coated on the positive electrode current collector, and then dried and roll-pressed to prepare the positive electrode active material layer. The coating process may be carried out by methods such as gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, rod coating, or casting, etc., but is not limited thereto. The positive electrode active material layer may further contain an adhesive, and optionally may also contain an electrolyte, a conductive material, a thickening agent, etc.

[0237] Solvents used to prepare the positive electrode active material layer 230 may include, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA), N,N-dimethylaminopropylamine (DMAPA), ethylene oxide (EO), tetrahydrofuran (THF), etc.

[0238] In one non-limiting embodiment, the electrolyte contained in the positive electrode active material layer 230 may be the electrolyte described above for a secondary battery. In another non-limiting embodiment, the electrolyte contained in the positive electrode active material may be the inorganic electrolyte described above. For example, the secondary battery may be provided in the form of an all-solid-state battery including the electrolyte described above or an inorganic electrolyte.

[0239] The adhesive may include polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethyl methacrylate, nitrile butadiene rubber (NBR), polybutadiene rubber (BR), and / or styrene-butadiene rubber (SBR), etc. In one non-limiting embodiment, the PVDF-based adhesive may be used as a positive electrode adhesive.

[0240] Conductive materials can be added to enhance the conductivity and / or lithium-ion or electron mobility of the positive electrode active material layer 230. For example, conductive materials may also include, but are not limited to, carbon-based conductive materials (e.g., graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc.) and / or metal-based conductive materials (including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc.).

[0241] The positive electrode active material layer 230 may also contain a thickener and / or a dispersant. In one non-limiting embodiment, the positive electrode active material layer 230 may contain a thickener, such as carboxymethyl cellulose (CMC).

[0242] The negative electrode 260 may include a negative electrode current collector 255 and a negative electrode active material layer 250 provided on at least one surface of the negative electrode current collector 255.

[0243] The negative electrode current collector 255 may include, for example, a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, and / or the like. In some non-limiting embodiments, the negative electrode current collector 255 may have a thickness of, for example, 10 μm to 50 μm, but is not limited thereto.

[0244] The negative electrode active material layer 250 may include a negative electrode active material. A material capable of intercalating and deintercalating lithium ions may be used as the negative electrode active material. In some non-limiting embodiments, the negative electrode active material may include: carbon-based materials, such as crystalline carbon, amorphous carbon, carbon composites, and / or carbon fibers, etc.; lithium metal; lithium alloys; silicon (Si)-containing materials and / or tin (Sn)-containing materials, etc.

[0245] In some non-limiting embodiments, examples of amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), and / or the like.

[0246] In some non-limiting embodiments, examples of crystalline carbon may include graphite-based carbon, such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and / or graphitized MPCF, etc.

[0247] The lithium metal may include pure lithium metal or lithium metal on which a protective layer for inhibiting dendrite growth is formed, etc. In one non-limiting embodiment, a lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one non-limiting embodiment, a lithium thin film layer may be used as the negative electrode active material layer.

[0248] Elements included in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc.

[0249] The silicon-containing material may provide higher capacity characteristics. The silicon-containing material may include Si, SiO x (0 < x < 2), metal-doped SiO x (0 < x < 2), silicon-carbon composites, etc. The metal may include lithium and / or magnesium, and metal-doped SiO x (0 < x < 2) may include metal silicates.

[0250] 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. The coating process can be carried out using essentially the same method as that used to prepare a positive electrode active material layer. The negative electrode active material layer may also contain a binder, and optionally may also contain an electrolyte, conductive material, thickener, etc.

[0251] In some non-limiting embodiments, the negative electrode 260 may also include a negative electrode active material layer 250 in the form of lithium metal formed by a deposition / coating process.

[0252] 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.

[0253] In one non-limiting embodiment, the electrolyte contained in the negative electrode active material layer 250 may be the electrolyte described above for a secondary battery. In another non-limiting 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 in the form of an all-solid-state battery including the electrolyte described above or an inorganic electrolyte.

[0254] The adhesive, conductive material, and thickener can be the same materials used in the manufacture of the positive electrode.

[0255] In some non-limiting embodiments, adhesives based on styrene-butadiene rubber (SBR), carboxymethyl cellulose, polyacrylic acid, and poly(3,4-ethylenedioxythiophene, PEDOT) can be used as negative electrode adhesives.

[0256] Figure 3 This is a schematic perspective view showing the structure of an electrolyte layer for a secondary battery according to some non-limiting embodiments.

[0257] Reference Figure 3 The electrolyte layer 210 may include the electrolyte 100 described above. For example, the electrolyte layer 210 may include a flame retardant compound 110 contained in the electrolyte 100. For example, the electrolyte layer 210 may include a membrane formed by impregnation and curing of the first mixed solution described above. The electrolyte layer 210 may be a membrane containing an electrolyte.

[0258] According to some non-limiting embodiments, the electrolyte layer 210 may be inserted between the positive electrode 240 and the negative electrode 260. For example, the electrolyte layer 210 may be a solid electrolyte layer comprising the aforementioned electrolyte.

[0259] According to some non-limiting embodiments, electrode unit 200 is defined by positive electrode 240, negative electrode 260 and electrolyte layer 210, and multiple electrode units 200 can be stacked to form an electrode assembly. For example, the electrode assembly can be formed by winding, stacking, folding, etc.

[0260] For example, electrode tabs (positive electrode tab and negative electrode tab) may protrude from the positive current collector 235 and the negative current collector 255, respectively, and may extend to one side of the housing. The electrode tabs may be fused to one side of the housing and connected to electrode leads (positive lead and negative lead) extending to or exposed outside the housing.

[0261] For example, bag-shaped shells, prism-shaped shells, cylindrical shells, coin-shaped shells, etc., can be used as shells.

[0262] In the following description, embodiments of the present disclosure will be further described with reference to specific experimental examples. However, the following embodiments and comparative examples included in the experimental examples are for illustrative purposes only, and those skilled in the art will clearly understand that various changes and modifications can be made within the scope and spirit of the present disclosure.

[0263] Examples and Comparative Examples

[0264] Example 1

[0265] (1) Preparation of electrolyte monomers

[0266] 100 mL of dichloromethane, 2.9 g (24.12 mmol) of 2-hydroxyethyl acrylate and 2.93 g (28.95 mmol) of triethylamine were introduced into the reactor to prepare a mixed solution.

[0267] After cooling the reactor to 0°C, 6.45 g (24.12 mmol) of diphenyl chlorophosphate was added to the mixed solution within 10 minutes.

[0268] The solution was then stirred at room temperature (25°C) for 24 hours, washed three times with water (H2O), and then dried under reduced pressure to remove the solvent in order to prepare a concentrated solution.

[0269] The concentrated solution was purified by column chromatography using hexane and ethyl acetate to obtain 6.5 g (yield: 77.4%) of electrolyte monomer.

[0270] The obtained electrolyte monomer is a compound represented by the above formula 2-1.

[0271] (2) Preparation of the first mixed solution

[0272] The compound represented by Formula 2-1 above and trimethylolpropane tri(meth)acrylate (TMPT(M)A) as the electrolyte monomer were mixed with 1.0 M LiPF6 solution (a solvent in which EC / EMC were mixed in a volume ratio of 3:7) to prepare a first mixed solution.

[0273] Based on the total weight of the first mixed solution, the content of the electrolyte monomer is 15 wt% (7.5 wt% of the compound represented by Formula 2-1 above and 7.5 wt% of TMPT(M)A), and the electrolyte monomer is used by mixing the compound represented by Formula 2-1 above and TMPT(M)A in a weight ratio of 1:1.

[0274] (3) Manufacturing of lithium secondary batteries

[0275] By mixing LiNi as the positive electrode active material in a weight ratio of 90:5:5 0.6 Co 0.2 Mn 0.2 The positive electrode slurry is prepared using O2, polyvinylidene fluoride (PVDF) as a binder, and carbon black as a conductive material. The positive electrode slurry is uniformly coated onto aluminum foil, then dried and rolled to manufacture the positive electrode.

[0276] 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 uniformly coated onto copper (Cu) foil, then dried and rolled to manufacture the negative electrode.

[0277] Polyethylene (PE) is prepared as a separator. The positive and negative electrodes are placed opposite each other with the separator in between, and the tabs of the positive and negative electrodes are welded on respectively.

[0278] The welded positive / separator / negative electrode assembly is placed in a bag, and then the bag is sealed on three sides except for one side through which the first mixed solution, serving as the electrolyte for the secondary battery, is injected. At this point, the portion with the tabs is included in the sealed portion. After the first mixed solution is injected through the remaining open side, and the remaining open side is also sealed, it is then allowed to be immersed for 12 hours or longer. Subsequently, a secondary battery containing the electrolyte for the secondary battery is manufactured by heat curing in an oven at 100°C for 1 hour.

[0279] Examples 2 to 11

[0280] During the preparation of the electrolyte for the secondary battery, the lithium secondary battery was manufactured in the same manner as in Example 1, except that the type and content of the electrolyte cells were changed as shown in Table 1 below.

[0281] Comparative Example 1

[0282] By mixing LiNi as the positive electrode active material in a weight ratio of 90:5:5 0.6 Co 0.2 Mn 0.2 A positive electrode slurry is prepared using O2, polyvinylidene fluoride (PVDF) as a binder, and carbon black as a conductive material. The positive electrode slurry is uniformly coated onto aluminum foil, then dried and rolled to manufacture the positive electrode.

[0283] 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 uniformly coated onto copper foil, then dried and rolled to manufacture the negative electrode.

[0284] Polyethylene (PE) is prepared as a separator. After the positive and negative electrodes are configured to face each other with the separator in between, the tabs of the positive electrode and the tabs of the negative electrode are welded on respectively.

[0285] The welded positive / separator / negative electrode assembly is placed in a bag, and then three sides of the bag are sealed except for the side used for electrolyte injection. At this point, the portion with the tabs is included in the sealed portion. After the electrolyte is injected through the remaining side, the remaining side is also sealed, and then it is allowed to be immersed for 12 hours or longer to manufacture a secondary battery.

[0286] A solution prepared by dissolving 1.0 M LiPF6 in EC / EMC (3 / 7; volume ratio) solvent was used as the electrolyte.

[0287] Comparative Example 2

[0288] During the preparation of the electrolyte for the secondary battery, the secondary battery was manufactured in the same manner as in Example 1, except that the type of electrolyte cell was changed as shown in Table 1 below.

[0289] Preparation of electrolyte monomers according to the examples

[0290] (1) Preparation of the compound (electrolyte monomer) represented by formula 3-1

[0291] 100 mL of dichloromethane, 4.82 g (41.52 mmol) of 2-hydroxyethyl acrylate and 5.04 g (49.82 mmol) of triethylamine were introduced into the reactor to prepare a mixed solution.

[0292] After cooling the reactor to 0°C, 7.16 g (41.52 mmol) of diethyl chlorophosphate was added to the mixed solution within 10 minutes.

[0293] The solution was then stirred at room temperature (25°C) for 24 hours, washed three times with water (H2O), and then dried under reduced pressure to remove the solvent, thus preparing a concentrated solution.

[0294] The concentrated solution was purified by column chromatography using hexane and ethyl acetate to obtain 5.87 g (yield: 56.1%) of electrolyte monomer.

[0295] The obtained electrolyte monomer is a compound represented by the above formula 3-1.

[0296] (2) Preparation of the compound represented by formula 2-2 (monomer for electrolyte)

[0297] 100 mL of tetrahydrofuran (THF), 10 g (96.02 mmol) of 2,2-dimethyl-1,3-propanediol and 24.3 g (240.04 mmol) of triethylamine were introduced into the reactor to prepare a mixed solution.

[0298] After cooling the reactor to 0°C, 14.73 g (96.02 mmol) of phosphoric acid chloride was added to the mixed solution over 30 minutes. The mixture was then stirred at room temperature (25°C) for 3 hours.

[0299] Subsequently, triethylamine hydrochloride was removed by filtration, and tetrahydrofuran (THF) was removed by vacuum drying to obtain the first concentrate.

[0300] The first concentrate was dissolved in 100 mL of dichloromethane, washed twice with water (H2O), and dried under reduced pressure to remove the solvent, in order to obtain the second concentrate.

[0301] The second concentrate was washed with hexane and water (H2O), filtered, and then vacuum dried to give 12.16 g (yield: 68.6%) of the intermediate.

[0302] The intermediate was dissolved in 100 mL of dichloromethane, followed by the addition of 10 g (98.83 mmol) of triethylamine and 7.65 g (65.89 mmol) of hydroxyethyl acrylate. The mixture was stirred at room temperature (25 °C) for 36 hours.

[0303] Subsequently, the mixture was washed once each with 1M aqueous hydrogen chloride (HCl), 1M aqueous sodium bicarbonate (NaHCO3), and water (H2O), and purified by column chromatography using hexane and ethyl acetate to obtain 5.74 g (yield: 33.1%) of electrolyte monomer.

[0304] The obtained electrolyte monomer is a compound represented by the above formula 2-2.

[0305] (3) Preparation of the compound (electrolyte monomer) represented by formula 4-1

[0306] 100 mL of dichloromethane, 5 g (32.45 mmol) of dimethyl (2-hydroxyethyl)phosphonate and 4.92 g (48.67 mmol) of triethylamine were introduced into the reactor to prepare a mixed solution.

[0307] After cooling the reactor to 0°C, add 3.23 g (35.70 mmol) of acryloyl chloride to the mixed solution within 10 minutes.

[0308] The solution was then stirred at room temperature for 24 hours, washed three times with water (H2O), and dried under reduced pressure to remove the solvent, thus preparing a concentrated solution.

[0309] The concentrated solution was purified by column chromatography using hexane and ethyl acetate to obtain 4.66 g (yield: 69.0%) of electrolyte monomer.

[0310] The obtained electrolyte monomer is a compound represented by the above formula 4-1.

[0311] [Table 1]

[0312]

[0313]

[0314] The specific components described in Table 1 are as follows.

[0315] A1: Compounds represented by Equation 2-1 above

[0316] A2: Compounds represented by Equation 3-1 above

[0317] A3: Compounds represented by Equation 2-2 above

[0318] A4: Compounds represented by Equation 4-1 above

[0319] TMPT(M)A: Trimethylolpropane tri(meth)acrylate

[0320] Experimental Example 1: Evaluation of Electrolytes

[0321] (1) Assessment of self-extinguishing property

[0322] 1) Examples 1 to 11 and Comparative Example 2

[0323] 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.

[0324] 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 Example 2. Then, the separator and cap were sequentially placed to assemble the coin cell.

[0325] Subsequently, dried glass fibers were placed and impregnated with the first mixed solution, and then cured at 70°C for 1 hour. The coin battery was then disassembled to prepare a sample (a sample of dried glass fibers cured with the first mixed solution), and the mass (g) of the sample was measured.

[0326] After igniting the sample, measure the time until the fire is extinguished (extinguishing time).

[0327] Calculate the self-extinguishing time using Equation 1 below.

[0328] [Equation 1]

[0329]

[0330] 2) Comparative Example 1

[0331] Glass fibers were cut into 16 μm diameter pieces and dried at 120°C to prepare dried glass fibers.

[0332] 3 ml of the electrolyte according to Comparative Example 1 above was placed in a sealed container and the mass (g) of the electrolyte was measured.

[0333] The dried glass fibers were then placed in a sealed container and impregnated with an electrolyte to prepare a sample. The sample was then removed, and the mass (g) of the unimpregnated residual electrolyte was measured.

[0334] After igniting the sample, measure the time until the fire is extinguished (extinguishing time).

[0335] Calculate the self-extinguishing time using Equation 2 below.

[0336] [Equation 2]

[0337]

[0338] The calculation results of the self-extinguishing time are shown in Table 2 below.

[0339] [Table 2]

[0340] Classification Self-extinguishing time (s / g) Example 1 67.11 Example 2 62.08 Example 3 66.38 Example 4 42.52 Example 5 58.09 Example 6 51.35 Example 7 34.20 Example 8 31.88 Example 9 35.11 Example 10 71.78 Example 11 28.98 Comparative Example 1 72.66 Comparative Example 2 70.05

[0341] Referring to Table 2, in the examples where at least one of A1 to A4 is used as an electrolyte monomer, the self-extinguishing time is 71.78 s / g or less.

[0342] In Comparative Example 1, which did not use an electrolyte monomer, the self-extinguishing time exceeded 72 s / g.

[0343] In Comparative Example 2, which used only trimethylolpropane tri(meth)acrylate (TMPT(M)A) as the electrolyte monomer, the self-extinguishing time was 70.05 s / g, which is longer than the self-extinguishing time of Examples 1 to 9, which used the same amount (7.5 wt%) of electrolyte monomer. Furthermore, in the case of Comparative Example 2, the initial capacity efficiency and cycle life retention were lower than those of the Examples.

[0344] Experimental Example 2: Evaluation of Lithium Secondary Batteries

[0345] (1) Measurement of initial capacity and evaluation of initial capacity efficiency

[0346] The lithium secondary batteries according to the above embodiments and comparative examples were charged in a chamber at 25°C (CC-CV 0.1C 4.3V 0.005C cutoff), and then the initial charge capacity was measured. They were then discharged (CC 0.1V 3.0V cutoff), and then the initial discharge capacity was measured.

[0347] Initial capacity efficiency is evaluated by calculating the percentage (%) of the value obtained by dividing the measured initial discharge capacity by the measured initial charge capacity.

[0348] The measured initial charge capacity and initial discharge capacity, as well as the evaluated initial capacity efficiency, are shown in Table 3 below.

[0349] (2) Assessment of cycle life retention

[0350] The lithium secondary batteries according to the above embodiments and comparative examples were repeatedly charged (CC / CV 0.5C 4.3V 0.05C cutoff) and discharged (CC 0.5C 2.7V cutoff) for 100 cycles at 25°C. The cycle life retention rate was then evaluated as a percentage (%) of the discharge capacity of the 100th cycle divided by the discharge capacity of the 1st cycle.

[0351] The evaluated cycle life retention rates are shown in Table 3 below.

[0352] [Table 3]

[0353]

[0354] Referring to Table 3, in the examples of lithium secondary batteries using an electrolyte comprising a polymer or copolymer containing at least one electrolyte monomer selected from A1 to A4, the initial capacity efficiency is 97.12% or higher, and the cycle life retention is 97.45% or higher, which is higher than the comparative examples.

[0355] In Examples 5 to 8, where at least one of the compounds represented by A1 and A2, and at least one of the compounds represented by A3 and A4, are used as electrolyte monomers, high initial discharge capacity, initial capacity efficiency, and cycle life retention are observed.

[0356] In Example 9, when A3 and A4 are used as a combination of electrolyte monomers, the initial capacity efficiency and cycle life retention are high.

[0357] In comparative examples using electrolyte cells other than A1 to A4 or electrolytes that do not include electrolyte cells, the initial charge capacity, initial capacity efficiency, and cycle life retention rate are reduced.

[0358] Although embodiments or aspects have been described in detail for illustrative purposes, it should be understood that such details are for illustrative purposes only, and this disclosure is not limited to the disclosed embodiments or aspects, but rather is intended to cover modifications and equivalent configurations within the spirit and scope of this disclosure. Furthermore, it should be understood that this disclosure takes into account that, to the extent possible, one or more features of any embodiment or aspect may be combined with one or more features of any other embodiment or aspect.

Claims

1. A monomer for use in an electrolyte, comprising a compound represented by Formula 1: [Formula 1] in, In Formula 1, R1 and R2 are each independently a substituted or unsubstituted C1 to C12 alkyl group or a substituted or unsubstituted C6 to C12 aromatic group, and R1 and R2 can be linked together to form a ring. R3 is a substituted or unsubstituted C1 to C5 alkylene group. R4 is hydrogen or a C1 to C5 alkyl group. m is between 1 and 5, and n is 0 or 1.

2. The monomer for electrolyte according to claim 1, wherein, R1 and R2 are each independently a substituted or unsubstituted C1 to C10 alkyl group, or a substituted or unsubstituted C6 to C10 aromatic group, and R1 and R2 can be linked together to form a ring. R3 is a C2 alkylene group. R4 is hydrogen or a C1 to C3 alkyl group, and m is 1 to 3.

3. The monomer for electrolytes according to claim 1, wherein, m is 1.

4. The monomer for electrolytes according to claim 1, wherein, n is 1, R1 and R2 are each independently a substituted or unsubstituted C6 to C10 aryl group, or a substituted or unsubstituted C1 to C7 alkyl group, and R3 is a substituted or unsubstituted C1 to C3 alkylene group; or n is 0, R1 and R2 are each independently substituted or unsubstituted C1 to C7 alkyl groups, and R3 is a substituted or unsubstituted C1 to C3 alkylene group.

5. The monomer for electrolytes according to claim 1, wherein, n is 1, R1 and R2 are each independently an unsubstituted C6 to C10 aryl or an unsubstituted C1 to C5 alkyl, and R3 is an unsubstituted C2 alkylene; or n is 0, R1 and R2 are each independently unsubstituted C1 to C5 alkyl groups, and R3 is an unsubstituted C2 alkylene group.

6. The monomer for an electrolyte according to claim 1, wherein, The monomer used for the electrolyte comprises at least one selected from the group consisting of compounds represented by the following formulas 2 to 4: [Equation 2] In Formula 2, R5 and R6 are each independently hydrogen, substituted or unsubstituted C1 to C5 alkyl, or substituted or unsubstituted C6 to C10 aryl, and R7 is hydrogen or C1 to C3 alkyl. [Formula 3] In formula 3, R8 and R9 are each independently hydrogen, or substituted or unsubstituted C1 to C3 alkyl groups, and R 10 It is hydrogen or C1 to C3 alkyl. [Formula 4] In Equation 4, R 11 and R 12 Each is independently hydrogen, or a substituted or unsubstituted C1 to C5 alkyl group, and R 13 It is hydrogen or C1 to C3 alkyl.

7. The monomer for an electrolyte according to claim 6, wherein, Compounds represented by Formula 1 include at least one selected from the group consisting of compounds represented by Formulas 2-1, 2-2, 3-1, and 4-1: [Equation 2-1] [Equation 2-2] [Equation 3-1] [Equation 4-1] 8. The monomer for an electrolyte according to claim 6, wherein, The monomer for the electrolyte includes at least one of the compounds represented by Formula 3 above, the compounds represented by Formula 4 above, and the compound represented by Formula 2 above.

9. The monomer for an electrolyte according to claim 6, wherein, The monomers used for the electrolyte include compounds represented by Formula 2 above and compounds represented by Formula 4 above.

10. An electrolyte for a secondary battery, comprising: Flame retardant compounds comprising polymers formed by monomer polymerization for electrolytes according to claim 1; and Lithium salts.

11. The electrolyte for a secondary battery according to claim 10, wherein, The content of the flame retardant compound is from 3 wt% to 60 wt%, based on the total weight of the electrolyte used in the secondary battery.

12. A lithium secondary battery, comprising: positive electrode; The negative electrode is positioned to face the positive electrode. as well as An electrolyte layer disposed between the positive electrode and the negative electrode and comprising the electrolyte for a secondary battery according to claim 10.

13. A method for preparing an electrolyte for a secondary battery, comprising: Prepare a first mixed solution comprising a monomer for electrolyte and an electrolyte solution as described in claim 1; as well as The first mixed solution is solidified.

14. The method for preparing an electrolyte for a secondary battery according to claim 13, wherein, The first mixed solution also contains organic polymers and inorganic electrolytes.

15. The method for preparing an electrolyte for a secondary battery according to claim 13, wherein, Based on the total weight of the first mixed solution, the content of the monomer used for the electrolyte is from 3 wt% to 60 wt%.

16. The method for preparing an electrolyte for a secondary battery according to claim 13, wherein, The first mixed solution also contains a thermal initiator, and The step of solidifying the first mixed solution includes heat treatment of the first mixed solution.

17. The method for preparing an electrolyte for a secondary battery according to claim 13, wherein, The first mixed solution also contains a photoinitiator, and The step of solidifying the first mixed solution includes irradiating the first mixed solution with light.

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