Electrolyte using high-dielectric-constant zwitterionic material, and preparation method therefor

Abstract

The present invention relates to an electrolyte using a high-dielectric-constant zwitterionic material, and a preparation method therefor. According to an embodiment, the provided electrolyte using a high-dielectric-constant zwitterionic material, which is for a secondary battery using a metal anode material as an anode, comprises an electrolyte mixture composed of: an organic electrolyte including an organic solvent and a metal salt; and a zwitterionic compound having a weight average molecular weight that satisfies a range of 100-60,000 g / mol and having a zwitterion.

Description

Electrolyte using high-k zwitterionic material and method for manufacturing the same

[0001] The present invention relates to an electrolyte using a high-dielectric constant zwitterionic material and a method for manufacturing the same.

[0002] Lithium-ion batteries are used in various industrial fields, and their importance as a core technology for electric vehicles is increasing. However, as lithium-ion battery fire incidents have recently emerged as a social issue, the demand for technology related to advanced battery technology and ensuring safety is increasing. Lithium metal has a high theoretical capacity of 3860 mAh / g, which is more than 10 times the theoretical capacity of 372 mAh / g of graphite, which is used as a commercialized anode material for existing lithium-ion batteries, and a low reduction potential (-3.04 V (vs. SHE), making it an essential material for reducing the weight and increasing the capacity of batteries.

[0003] However, the above lithium metal has the following problems.

[0004] As technological demands for advanced and lightweight batteries increase, the use of lithium metal as a next-generation anode material is essential. However, there is a limitation in that lithium ion deposition is concentrated in a specific area to thermodynamically stabilize the metal surface, which leads to the formation of lithium dendrites.

[0005] Accordingly, the development of electrolytes that impart interfacial stability to lithium secondary batteries by suppressing lithium metal dendrite formation is urgently needed. With the growing demand for advanced and lightweight batteries, the use of lithium metal as a next-generation anode material is essential. However, lithium ion deposition is concentrated in specific areas to thermodynamically stabilize the metal surface, leading to the formation of lithium dendrites.

[0006] Accordingly, there is a need to develop an electrolyte that provides interfacial stability between the electrolyte and the negative electrode to lithium secondary batteries by suppressing dendrite formation in lithium metal.

[0007] An electrolyte using a high-k zwitterionic material according to one embodiment of the present invention and a method for manufacturing the same are proposed to solve the above problems, and by using a zwitterionic material as an electrolyte additive, lithium dendrites generated during charge and discharge are suppressed, thereby imparting stability to the interface between the electrolyte and the negative electrode, thereby utilizing lithium metal as a negative electrode material of a battery and at the same time securing long-life and high-output characteristics of the battery.

[0008] According to one embodiment, an electrolyte using a high-k zwitterionic material for a secondary battery utilizing a metal anode material as a cathode may be provided, the electrolyte including an electrolyte mixture comprising an organic electrolyte including an organic solvent and a metal salt; and a zwitterionic compound having a zwitterion and having a weight average molecular weight in the range of 100 to 60,000 g / mol.

[0009] In addition, the electrolyte mixture may be provided as an electrolyte using a high-dielectric constant zwitterionic material, comprising 90 to 99.5 wt% of the organic electrolyte and 0.5 to 10 wt% of the zwitterionic compound.

[0010] In addition, the organic electrolyte may be provided using a high-dielectric constant zwitterionic material in which the metal salt is dissolved in the organic solvent at a concentration of 1 M to 4 M.

[0011] In addition, an electrolyte using a high-k zwitterionic material can be provided, wherein the zwitterionic compound is at least one compound selected from among a first zwitterionic compound including a zwitterionic monomer; a second zwitterionic compound derived from the zwitterionic monomer and polymerized through an initiator; a third zwitterionic compound derived from the zwitterionic monomer and polymerized through a crosslinking agent and an initiator; and a fourth zwitterionic compound derived from a combination of a cationic monomer and an anionic monomer and polymerized through an initiator.

[0012] In addition, an electrolyte using a high-k zwitterionic material, wherein the zwitterionic monomer is at least one material selected from the group consisting of 2-Methacryloyloxyethyl phosphorylcholine (MPC), 3-[[2-(Methacryloyloxy)ethyl]dimethylammonio] propoinate, and Sulfobetainemethacrylate, can be provided.

[0013] In addition, an electrolyte using a high-k zwitterionic material can be provided, wherein the cationic monomer is at least one material selected from the group consisting of METAC, AETMA, and AMPTMA ((3-Acrylamidopropyl) trimethylammonium chloride), and the anionic monomer is at least one material selected from the group consisting of SPA, SPM (3-Sulfopropyl methacrylate), and AMPA.

[0014] In addition, an electrolyte using a high-dielectric constant zwitterionic material, which has a dielectric constant value higher than that of the organic solvent and increases the dielectric constant of the electrolyte mixture to stabilize the interface between the electrolyte and the metal negative electrode material, can be provided.

[0015] In addition, an electrolyte using a high-k zwitterionic material can be provided, in which the zwitterionic compound forms a polarized field on the surface of the metal anode material, thereby suppressing the formation of metal dendrites due to biased deposition of metal ions.

[0016] In addition, an electrolyte using a high-k zwitterionic material can be provided, wherein the organic solvent includes at least one material selected from the group consisting of ethylene carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0017] In addition, the metal salt is a lithium salt selected from the group consisting of lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N, LiTFSI), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis-perfluoroethylsulfonylimide (Li(C2F5SO2)2N), lithium thiocyanate (LiSCN), lithium triflate (LiCF3SO3), lithium tetrafluoroaluminate (LiAlF4), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2, LiFSI) and mixtures thereof, using a high-k zwitterionic material. Electrolytes may be provided.

[0018] In addition, an electrolyte using a high-k zwitterionic material can be provided, wherein the crosslinking agent includes any one material selected from the group consisting of poly(ethyleneglycol) diacrylate and trimetylopropane troacrylate, and the initiator includes any one material selected from the group consisting of ammonium persulfate, 2.2'-Azobisisobutylonitrile, Photoinitiator 184, and Photoinitiator 2959.

[0019] According to one embodiment, a method for manufacturing an electrolyte using a high-k zwitterionic material for a secondary battery utilizing a metal anode material as a cathode may be provided, the method including: a first step of preparing an organic electrolyte including an organic solvent and a metal salt; and a second step of preparing an electrolyte mixture by mixing a zwitterionic compound having a zwitterionic compound and a weight average molecular weight satisfying a range of 100 to 60,000 g / mol with the prepared organic electrolyte.

[0020] According to one embodiment, a secondary battery may be provided, including: a positive electrode; a negative electrode including a metal negative electrode material; an electrolyte disposed between the positive electrode and the negative electrode and using a high-k zwitterionic material according to any one of claims 1 to 8; and a separator positioned on the electrolyte using the high-k zwitterionic material.

[0021] An electrolyte using a high-k zwitterionic material according to one embodiment of the present invention and a method for manufacturing the same have the effect of providing stability to the interface between the electrolyte and the negative electrode by suppressing lithium dendrites generated during charge and discharge by using the zwitterionic material as an electrolyte additive, thereby enabling the use of lithium metal as a negative electrode material of a battery and at the same time securing long-life and high-output characteristics of the battery.

[0022] FIG. 1 is a drawing for explaining a high-k binary ion material according to embodiments of the present invention.

[0023] Figure 2 is a flow chart for explaining a method for manufacturing an electrolyte using a high-k binary ion material according to embodiments of the present invention.

[0024] Figure 3 is a diagram showing the dielectric constant values ​​of the electrolytes according to Example 1 and Comparative Example 1.

[0025] FIG. 4 is a drawing showing the shape of the lithium metal surface after charging and discharging in a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0026] Figure 5 is a diagram showing charge / discharge curves obtained from constant current measurements in a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0027] Figure 6 is a drawing showing the flatness of the charge / discharge curve obtained from constant current measurement in the secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2 by dividing it into sections.

[0028] Figure 7 is a drawing showing the results of analyzing the lithium metal surface composition using an energy dispersive spectrometer after charging and discharging of a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0029] Figure 8 is a drawing showing the results of analyzing the lithium metal surface composition using an X-ray photoelectron spectrometer after charging and discharging of a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0030] Figure 9 shows the results of constant current charge / discharge evaluation of lithium secondary battery coin cells according to Example 3 and Comparative Example 3.

[0031] In order to fully understand the configuration and effect of the present invention, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0032] The present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications and changes. However, the description of these embodiments is provided to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the present invention of the scope of the invention. In the attached drawings, components are illustrated in enlarged size for convenience of explanation, and the proportions of each component may be exaggerated or reduced.

[0033] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In addition, the terms used herein can be interpreted as having the meaning commonly known to those of ordinary skill in the art, unless otherwise defined. In this specification, the singular also includes the plural unless specifically stated in the phrase. As used herein, the words "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, operations, and / or elements mentioned.

[0034] When a layer is referred to herein as being "on" another layer, it may be formed directly on the surface of the other layer, or a third layer may be interposed therebetween. Although terms such as first, second, etc. are used herein to describe various regions, layers, etc., these regions and layers should not be limited by such terms. These terms are only used to distinguish a given region or layer from another region or layer. Thus, a part referred to as a first part in one embodiment may be referred to as a second part in another embodiment. The embodiments described and illustrated herein also include complementary embodiments thereof. Parts denoted by the same reference numerals throughout the specification represent like elements.

[0035] The electrolyte using the high-dielectric constant zwitterionic material of the present invention is designed to increase the dielectric constant of the electrolyte and stabilize the interface between the electrolyte and the metal negative electrode material.

[0036] Specifically, in the present invention, by adding a zwitterionic material to the electrolyte as an electrolyte additive, an electrolyte using a high-k zwitterionic material capable of effectively suppressing dendrite growth on the surface of a metal anode material through polarization was secured.

[0037]

[0038] Electrolyte using high-k zwitterionic material

[0039] FIG. 1 is a drawing for explaining a high-k binary ion material according to embodiments of the present invention.

[0040] Figure 1a) is a drawing for explaining a manufacturing process of a high-dielectric constant zwitterionic material, and Figure 1b) is a drawing for explaining a coin cell including a high-dielectric constant zwitterionic material.

[0041] Referring to FIG. 1a), an electrolyte using a high-k zwitterionic material for a secondary battery utilizing a metal anode material as a cathode according to one embodiment of the present invention includes an organic electrolyte including an organic solvent and a metal salt, and an electrolyte mixture composed of a zwitterionic compound having a zwitterion and a weight average molecular weight satisfying a range of 100 to 60,000 g / mol.

[0042] Specifically, the present invention may be an electrolyte using a high-dielectric constant zwitterionic material that can be used in a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a zinc secondary battery, an aluminum secondary battery, and a magnesium secondary battery, each of which utilizes lithium metal, sodium metal, potassium metal, zinc metal, aluminum metal, and magnesium metal as a negative electrode, and more specifically, it is preferable that the electrolyte use a high-dielectric constant zwitterionic material for a lithium secondary battery that utilizes lithium metal as a negative electrode.

[0043] In addition, it may be composed of 90 to 99.5 wt% of the organic electrolyte and 0.5 to 10 wt% of the zwitterionic compound.

[0044] Here, the organic electrolyte may be a metal salt dissolved in the organic solvent at a concentration of 1 M to 4 M.

[0045] According to a preferred embodiment of the present invention, an electrolyte using a high-dielectric constant zwitterionic material may be an electrolyte containing a zwitterionic compound, i.e., a liquid electrolyte, and may have a high dielectric constant value, and the zwitterionic compound may be a monomer or polymer having a zwitterion.

[0046] More specifically, the zwitterionic compound may be a zwitterionic polymer derived from a monomer having the zwitterion or derived from a cationic monomer and an anionic monomer.

[0047] In addition, the metal negative electrode material may include lithium metal, sodium metal, potassium metal, zinc metal, aluminum metal, and magnesium metal, and may be used as a negative electrode of a lithium secondary battery and a next-generation secondary battery such as a sodium secondary battery, a potassium secondary battery, a zinc secondary battery, an aluminum secondary battery, and a magnesium secondary battery.

[0048] Such an electrolyte containing a zwitterionic compound can suppress metal dendrite growth on the surface of a metal anode material and side reactions with the electrolyte.

[0049] According to one embodiment of the present invention, the metal anode material is preferably lithium metal, and more specifically, the electrolyte including a zwitterionic compound suppresses lithium dendrite growth on the surface of the lithium metal and side reactions with the electrolyte.

[0050]

[0051] (1) Organic solvents and metal salts

[0052] The organic solvent according to one embodiment of the present invention is not particularly limited as long as it dissolves the component materials well and has low reactivity with the metal anode material.

[0053] The organic solvent according to the present invention may include a conventional organic solvent, specifically, at least one substance selected from the group consisting of ethylene carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0054] The metal salt according to one embodiment of the present invention is not particularly limited as long as it helps improve ionic conductivity, and may vary depending on the type of the metal anode material.

[0055] The metal salt according to a preferred embodiment of the present invention may be a lithium salt selected from the group consisting of conventional lithium salts, specifically, lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N, LiTFSI), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis-perfluoroethylsulfonylimide (Li(C2F5SO2)2N), lithium thiocyanate (LiSCN), lithium triflate (LiCF3SO3), lithium tetrafluoroaluminate (LiAlF4), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2, LiFSI), and mixtures thereof. there is.

[0056]

[0057] (2) Zwitterionic compounds

[0058] The zwitterionic compound according to one embodiment of the present invention is not particularly limited as long as it is a compound that can include both a cationic functional group and an anionic functional group.

[0059] The zwitterionic compound according to the present invention comprises a conventional monomer or polymer, and specifically, at least one compound selected from a first zwitterionic compound comprising a zwitterionic monomer, a second zwitterionic compound derived from the zwitterionic monomer and polymerized via an initiator, a third zwitterionic compound derived from the zwitterionic monomer and polymerized via a crosslinking agent and an initiator, and a fourth zwitterionic compound derived from a combination of a cationic monomer and an anionic monomer and polymerized via an initiator.

[0060] In one embodiment of the present invention, the first zwitterionic compound may have a weight average molecular weight in the range of 100 to 400 g / mol, the second zwitterionic compound may have a weight average molecular weight in the range of 5000 to 15000 g / mol, the third zwitterionic compound may have a weight average molecular weight in the range of 30000 to 60000 g / mol, and the fourth zwitterionic compound may have a weight average molecular weight in the range of 5000 to 15000 g / mol.

[0061] The above-mentioned zwitterionic monomer may be at least one material selected from the group consisting of 2-Methacryloyloxyethyl phosphorylcholine (MPC), 3-[[2-(Methacryloyloxy)ethyl]dimethylammonio] propoinate, and Sulfobetainemethacrylate, and may have a higher dielectric constant value than a conventional material having a zwitterionic monomer, and thus may be used as an electrolyte additive to increase the dielectric constant of the electrolyte.

[0062] In addition, the cationic monomer may be at least one material selected from the group consisting of METAC, AETMA, and AMPTMA ((3-Acrylamidopropyl) trimethylammonium chloride), and the anionic monomer may be at least one material selected from the group consisting of SPA, SPM (3-Sulfopropyl methacrylate), and AMPA.

[0063] In other words, the zwitterionic compound has a higher dielectric constant than the organic solvent, and can increase the dielectric constant of the electrolyte mixture to stabilize the interface between the electrolyte and the metal negative electrode material.

[0064] Accordingly, the above-mentioned zwitterionic compound forms a polarized field on the surface of the metal anode material, thereby suppressing the formation of metal dendrites due to biased deposition of metal ions, thereby imparting interface stability to a secondary battery utilizing the metal anode material as the anode.

[0065] More specifically, the polarization field can be formed on the surface of a metal cathode material having a relatively (-) polarity, with the cations included in the zwitterionic compound being arranged in the direction of the metal cathode material and the anions being arranged in the direction of the electrolyte, and the formation of such a polarization field can ensure uniform movement of the metal ions.

[0066] Accordingly, the zwitterionic compound can increase the dielectric constant of the electrolyte mixture to stabilize the interface between the electrolyte and lithium metal, and can form a polarized field on the surface of the lithium metal to suppress the formation of lithium dendrites due to biased deposition of lithium ions, thereby imparting interface stability to a lithium secondary battery utilizing lithium metal as an anode.

[0067] Meanwhile, as described above, the zwitterionic compound may be at least one compound selected from a first zwitterionic compound, a second zwitterionic compound, a third zwitterionic compound, and a fourth zwitterionic compound, wherein the second zwitterionic compound may be formed by heat-treating or UV-treating a first monomer mixture comprising a mixture of the zwitterionic monomer and the initiator and a solvent, depending on the type of initiator.

[0068] In addition, the third zwitterionic compound can be formed by heat-treating or UV-treating a second monomer mixture consisting of a mixture of the zwitterionic monomer, a crosslinking agent, and an initiator and a solvent, depending on the type of initiator.

[0069] In addition, the fourth zwitterionic compound can be formed by heat-treating or UV-treating a third monomer mixture consisting of a mixture of a cationic monomer, an anionic monomer, and an initiator and a solvent, depending on the type of initiator.

[0070] At this time, it is preferable that the solvent is water.

[0071]

[0072] (3) Crosslinking agent and initiator

[0073] The crosslinking agent according to one embodiment of the present invention may include any one material selected from the group consisting of conventional crosslinking agents, for example, poly(ethyleneglycol) diacrylate and trimethylolpropane triacrylate, and is not limited to a specific crosslinking agent, but is preferably poly(ethyleneglycol) diacrylate, which has excellent mechanical properties of a crosslinked structure obtained through a crosslinking reaction and excellent chemical resistance and electrochemical stability.

[0074] The initiator according to one embodiment of the present invention is not particularly limited as long as it can initiate a polymerization reaction or a crosslinking reaction.

[0075] The initiator according to the present invention may include any one material selected from the group consisting of a conventional initiator, for example, ammonium persulfate, 2.2'-Azobisisobutylonitrile, Photoinitiator 184, and Photoinitiator 2959, and is not limited to a specific initiator, but preferably, ammonium persulfate, which can excellently initiate a crosslinking reaction.

[0076]

[0077] Secondary battery coin cell ​

[0078] Referring to FIG. 1b), a secondary battery coin cell includes a positive electrode, a negative electrode including a metal negative electrode material, an electrolyte using a high-k zwitterionic material of the present invention disposed between the positive electrode and the negative electrode, and a separator positioned on the electrolyte using the high-k zwitterionic material.

[0079] The positive and negative electrodes according to the present invention may be conventionally known positive and negative electrodes and are not limited to specific negative and positive electrodes. However, preferably, the negative electrode may include lithium metal, which is a metal negative electrode material. In addition, a symmetrical cell using metal for both the positive and negative electrodes can be manufactured, and when lithium metal is used, it corresponds to a secondary battery lithium symmetrical cell.

[0080] The above positive and negative electrodes can be arranged on an electrolyte using a high-k zwitterionic material of the present invention, that is, the electrolyte using a high-k zwitterionic material according to the present invention includes a zwitterionic compound as an electrolyte additive, thereby forming a polarization field on the surface of lithium metal to uniformly move lithium ions, thereby preventing the conventional biased deposition of lithium ions, thereby effectively suppressing the growth of lithium dendrites.

[0081]

[0082] Method for manufacturing electrolyte using high-dielectric constant zwitterionic material

[0083] Figure 2 is a flow chart for explaining a method for manufacturing an electrolyte using a high-k binary ion material according to embodiments of the present invention.

[0084] Referring to FIG. 2, an electrolyte using a high-k material according to one embodiment of the present invention and a method for manufacturing the same (S10) include a first step (S100) of preparing an organic electrolyte including an organic solvent and a lithium salt, and a second step (S200) of preparing an electrolyte mixture by mixing a zwitterionic compound having a weight average molecular weight in the range of 100 to 60,000 g / mol and having a zwitterion into the prepared organic electrolyte. ​

[0085] The above step S100 relates to an organic electrolyte preparation process, and refers to a process of preparing an organic electrolyte by mixing an organic solvent and a lithium salt prior to manufacturing an electrolyte using the high-k double-ion material of the present invention.

[0086] Specifically, in the step S100, the organic electrolyte may be prepared by dissolving the lithium salt in the organic solvent at a concentration of 1 M to 4 M. That is, the lithium salt may be added to 1 L of the organic solvent at a concentration of 1 M to 4 M.

[0087] Next, the S200 step is a process for preparing a zwitterionic compound and additionally mixing the prepared zwitterionic compound into the organic electrolyte prepared in the S100 step to increase the overall dielectric constant of the electrolyte.

[0088] Specifically, the S200 step may include a preparation step of preparing a zwitterionic compound; and a stirring step of mixing and stirring the prepared organic electrolyte and the prepared zwitterionic compound.

[0089] The above preparation step may vary depending on the type of the zwitterionic compound, and specifically, when the zwitterionic compound is a first zwitterionic compound including a zwitterionic monomer, a first zwitterionic compound is prepared that is at least one substance selected from the group consisting of 2-Methacryloyloxyethyl phosphorylcholine (MPC), 3-[[2-(Methacryloyloxy)ethyl]dimethylammonio] propoinate, and Sulfobetainemethacrylate.

[0090] In addition, in the above preparation step, when the zwitterionic compound is a second zwitterionic compound, a first monomer mixture consisting of a mixture of the zwitterionic monomer and the initiator and a solvent is prepared, and the prepared first monomer mixture is cast on a substrate, and then cured through heat treatment or UV treatment depending on the type of the initiator to prepare a second zwitterionic compound.

[0091] In addition, in the above preparation step, when the zwitterionic compound is a third zwitterionic compound, a second monomer mixture consisting of a mixture of the zwitterionic monomer, a crosslinking agent, and an initiator and a solvent is prepared, and the prepared second monomer mixture is cast on a substrate, and then cured through heat treatment or UV treatment depending on the type of the initiator to prepare the third zwitterionic compound.

[0092] In addition, in the above preparation step, when the zwitterionic compound is a fourth zwitterionic compound, a third monomer mixture consisting of a mixture of a cationic monomer, an anionic monomer, and an initiator and a solvent is prepared, and the prepared third monomer mixture is cast on a substrate, and then cured through heat treatment or UV treatment depending on the type of the initiator to prepare the fourth zwitterionic compound.

[0093] Next, in the stirring step, the stirring process may be a process of mixing the organic electrolyte prepared in step S100 and the prepared zwitterionic compound, which is at least one compound selected from the first zwitterionic compound, the second zwitterionic compound, the third zwitterionic compound, and the fourth zwitterionic compound, and stirring at a speed of 300 rpm for 1 to 3 hours in a room temperature atmosphere to prepare an electrolyte mixture.

[0094] Additionally, in the stirring step, the electrolyte mixture can be prepared to be composed of 90 to 99.5 wt% of the organic electrolyte and 0.5 to 10 wt% of the zwitterionic compound.

[0095]

[0096] The present invention is described in more detail through the following examples. These examples are provided merely as examples to aid understanding of the present invention and are not intended to limit the scope of the present invention.

[0097]

[0098] Example 1: Preparation of electrolyte using high-k zwitterionic material

[0099] First, an organic solvent was prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, and lithium hexafluorophosphate, a lithium salt, was dissolved in the prepared organic solvent at a concentration of 1 M to prepare an organic electrolyte.

[0100] Next, 987.5 g of the prepared organic electrolyte and 12.5 g of the first zwitterionic compound, the zwitterionic monomer Methacryloyloxyethyl phosphorylcholine (MPC), were mixed, and stirred at a speed of 300 rpm for 1 to 3 hours at room temperature to prepare an electrolyte mixture, thereby preparing an electrolyte using a high-k zwitterionic material including an electrolyte mixture composed of 98.75 wt% of the organic electrolyte and 1.25 wt% of the zwitterionic compound (Example 1).

[0101]

[0102] Example 2: Manufacturing of a secondary battery lithium metal symmetric cell containing an electrolyte using a high-k zwitterionic material.

[0103] A secondary battery lithium metal symmetrical cell was manufactured using an electrolyte using the high-k zwitterionic material of Example 1, lithium metal as both the anode and cathode, and a polyethylene separator as the separator (Example 2).

[0104]

[0105] Example 3: Manufacturing of a lithium secondary battery coin cell including an electrolyte using a high-k zwitterionic material. ​​

[0106] A lithium secondary battery coin cell was manufactured using an electrolyte using the high-k double-ion material of Example 1, lithium metal as a negative electrode, a positive electrode including a positive electrode active material, and a polyethylene separator as a separator (Example 3).

[0107]

[0108] Comparative Example 1: Preparation of Organic Electrolyte

[0109] An organic solvent was prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1:1, and lithium hexafluorophosphate, a lithium salt, was dissolved in the prepared organic solvent at a concentration of 1 M to prepare an organic electrolyte (Comparative Example 1).

[0110]

[0111] Comparative Example 2: Manufacturing of a secondary battery lithium metal symmetric cell containing an organic electrolyte

[0112] A secondary battery lithium metal symmetrical cell was manufactured using the organic electrolyte of Comparative Example 1, lithium metal as both the anode and cathode, and a polyethylene separator as the separator (Comparative Example 2).

[0113]

[0114] Comparative Example 3: Manufacturing of a lithium secondary battery coin cell containing an organic electrolyte

[0115] A lithium secondary battery coin cell was manufactured using the organic electrolyte of Comparative Example 1, lithium metal as a negative electrode, a positive electrode including a positive electrode active material, and a polyethylene separator as a separator (Comparative Example 3).

[0116]

[0117] Experimental Example 1: Measurement of the dielectric constant of electrolyte

[0118] The dielectric constant of the electrolyte manufactured according to Example 1 and Comparative Example 1 was measured at six frequencies using a dielectric spectrometer, and the results are shown in Fig. 3.

[0119] ​Figure 3 is a diagram showing the dielectric constant values ​​of the electrolytes according to Example 1 and Comparative Example 1.

[0120] Figure 3a) shows the dielectric constant measurement result of the electrolyte according to Comparative Example 1, and Figure 3b) shows the dielectric constant measurement result of the electrolyte according to Example 1.

[0121] As shown in FIG. 3, the dielectric constant value of the electrolyte according to Example 1 was measured to be much higher than the dielectric constant value of the electrolyte according to Comparative Example 1, which means that the electrolyte with the added zwitterionic material has a higher interfacial charge distribution than the general organic electrolyte, and this appears to be because the zwitterionic material present in the electrolyte according to Example 1 forms a strong polarization field at the interface.

[0122]

[0123] Experimental Example 2: Evaluation of the Surface Shape of Lithium Metal

[0124] A charge / discharge test of a secondary battery lithium metal symmetrical cell according to Example 2 and Comparative Example 2 was performed 5 times, and the surface shape of the negative electrode lithium metal was observed using a scanning electron microscope, and the results are shown in Fig. 4.

[0125] FIG. 4 is a drawing showing the shape of the lithium metal surface after charging and discharging in a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0126] FIG. 4a) is a drawing showing the movement of lithium ions at the electrolyte / lithium metal interface of the secondary battery lithium metal symmetrical cell according to Comparative Example 2, FIG. 4b) is a drawing showing the surface shape of lithium metal of the secondary battery lithium metal symmetrical cell according to Comparative Example 2, FIG. 4c) is a drawing showing the movement of lithium ions at the electrolyte / lithium metal interface of the secondary battery lithium metal symmetrical cell according to Example 2, and FIG. 4d) is a drawing showing the surface shape of lithium metal of the secondary battery lithium metal symmetrical cell according to Example 2.

[0127] Referring to FIG. 4a) and FIG. 4b), it can be seen that the surface shape of the lithium metal of the secondary battery lithium metal symmetrical cell according to Comparative Example 2 is uneven and lithium dendrites like tree trunks are formed due to biased deposition caused by non-uniform movement of lithium ions.

[0128] On the other hand, referring to FIG. 4c) and FIG. 4d), it was confirmed that the lithium metal surface shape of the secondary battery lithium metal symmetric cell according to Example 2 was uniformly formed with circular lithium as no biased deposition occurred due to the uniform movement of lithium ions.

[0129]

[0130] Experimental Example 3: Constant Current Charge-Discharge Evaluation of a Lithium Symmetric Cell

[0131] A charge / discharge test of a secondary battery lithium metal symmetrical cell according to Example 2 and Comparative Example 2 was performed 150 times, and the constant current charge / discharge curves thereof are shown in FIGS. 5 and 6.

[0132] Figure 5 is a diagram showing charge / discharge curves obtained from constant current measurements in a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0133] Figure 5a) is a charge / discharge curve of a secondary battery lithium metal symmetrical cell according to Comparative Example 2, and Figure 5b) is a charge / discharge curve of a secondary battery lithium metal symmetrical cell according to Example 2.

[0134] Figure 6 is a drawing showing the flatness of the charge / discharge curve obtained from constant current measurement in the secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2 by dividing it into sections.

[0135] FIG. 6a) is a diagram showing a charge / discharge curve and the flatness of the curve between 10 and 20 hours of a secondary battery lithium metal symmetrical cell according to Comparative Example 2, FIG. 6b) is a diagram showing a charge / discharge curve and the flatness of the curve between 10 and 20 hours of a secondary battery lithium metal symmetrical cell according to Example 2, FIG. 6c) is a diagram showing a charge / discharge curve and the flatness of the curve between 60 and 70 hours of a secondary battery lithium metal symmetrical cell according to Comparative Example 2, FIG. 6d) is a diagram showing a charge / discharge curve and the flatness of the curve between 60 and 70 hours of a secondary battery lithium metal symmetrical cell according to Example 2, FIG. 6e) is a diagram showing a charge / discharge curve and the flatness of the curve between 120 and 130 hours of a secondary battery lithium metal symmetrical cell according to Comparative Example 2, and FIG. 6f) is a diagram showing a charge / discharge curve and the flatness of the curve between 120 and 130 hours of a secondary battery lithium metal symmetrical cell according to Example 2 This is a drawing showing a charge / discharge curve and the flatness of the curve between 120 and 130 hours, and FIG. 6g) is a drawing showing a charge / discharge curve and the flatness of the curve between 190 and 200 hours of a secondary battery lithium metal symmetrical cell according to Example 2.

[0136] As shown in Fig. 5, the secondary battery lithium metal symmetric cell according to Comparative Example 2 showed a sharp increase in voltage polarization after about 80 hours, which is a phenomenon resulting from dead lithium formed due to dendrite growth on the surface of the lithium metal, and a section where the voltage polarization suddenly dropped also appeared, which indicates that the lithium metals of the positive and negative electrodes were directly connected due to extreme dendrite growth.

[0137] On the other hand, the secondary battery lithium metal symmetric cell according to Example 2 did not show a sharp rise or fall in voltage polarization during 300 hours of charge and discharge, indicating that dendrite growth on the lithium metal surface was significantly suppressed.

[0138] In Fig. 6, the flatness represents the difference between the maximum voltage value in one charge or discharge curve and the minimum voltage value in the pit portion.

[0139] As shown in FIGS. 6a), 6c), and 6e), based on the flatness of 60.7 mV calculated from the curve within the charge-discharge section between 10 and 20 hours of the secondary battery lithium metal symmetrical cell according to Comparative Example 2, the flatness calculated from the curve within the charge-discharge section between 60 and 70 hours decreased by approximately 33.3%, and when referring to FIG. 5, it was confirmed that the shape of the curve within the charge-discharge section between 120 and 130 hours was completely destroyed, as if the function of the cell had rapidly deteriorated after approximately 80 hours.

[0140] As shown in Fig. 6b), the flatness calculated from the curve within the charge-discharge section between 10 and 20 hours of the lithium metal symmetrical cell of the secondary battery according to Example 2 is 14.8 mV, which is much lower than 60.7 mV of the lithium metal symmetrical cell of the secondary battery according to Comparative Example 2. It is believed that this is because the strong polarization field of the interface formed from the zwitterionic material in the electrolyte uniformly distributed the lithium ion flux.

[0141] As shown in FIGS. 6d), 6f), and g), the calculated flatness in the curve within the charge-discharge section between 60 and 70 hours was reduced by approximately 8.8% based on the flatness calculated in FIG. 6b), the calculated flatness in the curve within the charge-discharge section between 120 and 130 hours was reduced by approximately 2.8%, and the calculated flatness in the charge-discharge section between 190 and 200 hours was reduced by approximately 10.9%, indicating that the strong polarization field at the interface formed from the zwitterionic material in the electrolyte made the lithium ion flux uniform, thereby significantly improving the life characteristics of the lithium metal symmetric cell.

[0142]

[0143] Experimental Example 4: Evaluation of the Surface Composition of Lithium Metal

[0144] A charge / discharge test of a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2 was performed 5 times, and the surface composition of the negative electrode lithium metal was observed based on an energy dispersive spectrometer and an X-ray photoelectron spectrometer. The results are shown in FIGS. 7 and 8.

[0145] Figure 7 is a drawing showing the results of analyzing the lithium metal surface composition using an energy dispersive spectrometer after charging and discharging of a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0146] FIG. 7a) is a drawing showing the location of elemental analysis of a lithium metal surface according to Comparative Example 2, FIG. 7b) is a drawing showing the location of elemental analysis of a lithium metal surface according to Example 2, FIG. 7c) is a drawing showing the lithium metal surface composition value according to Comparative Example 2, and FIG. 7d) is a drawing showing the lithium metal surface composition value according to Example 2.

[0147] Figure 8 is a drawing showing the results of analyzing the lithium metal surface composition using an X-ray photoelectron spectrometer after charging and discharging of a secondary battery lithium metal symmetric cell according to Example 2 and Comparative Example 2.

[0148] FIG. 8a) is a drawing showing the lithium metal surface composition according to Comparative Example 2, and FIG. 8b) is a drawing showing the lithium metal surface composition according to Example 2.

[0149] As shown in FIG. 7, the lithium metal surface composition information of the lithium metal symmetrical cell of the secondary battery according to Example 2 and the lithium metal surface composition information of the lithium metal symmetrical cell of the secondary battery according to Comparative Example 2 do not show a large difference, and in particular, the proportion of nitrogen element is about 6% in the lithium metal according to Example 2 and about 3% in the lithium metal according to Comparative Example 2, which is lower than the nitrogen element value of 7% in the lithium metal before charging and discharging.

[0150] Therefore, the low nitrogen element ratio of the lithium metal according to Example 2 indicates that the zwitterion MPC containing nitrogen atoms in the electrolyte was not decomposed during the charge / discharge process.

[0151] As shown in FIG. 8, when the lithium metal surface composition was analyzed after charge and discharge of the secondary battery lithium metal symmetric cell according to Comparative Example 2, the nitrogen 1s peak on the lithium metal surface was not detected. This confirms that the nitrogen 1s peak does not appear because nitrogen atoms do not exist in the electrolyte. When the lithium metal surface composition was analyzed after charge and discharge of the secondary battery lithium metal symmetric cell according to Example 2, it was determined that the nitrogen 1s peak appeared because the zwitterion MPC containing nitrogen atoms in the electrolyte was not decomposed during the charge and discharge process.

[0152]

[0153] Experimental Example 5: Constant Current Charge / Discharge Evaluation of Coin Cells

[0154] A charge / discharge test of a lithium secondary battery coin cell according to Example 3 and Comparative Example 3 was performed 189 times, and the rate characteristics and life characteristics results are shown in Fig. 9.

[0155] The constant current charge / discharge evaluation of the coin cell was based on constant current measurement and the current was set to 1C = 200 mA / g. For the rate test, charge / discharge was performed 5 times at currents of 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, and 5 C, and then charge / discharge was performed at 1 C for the life test.

[0156] Figure 9 shows the results of constant current charge / discharge evaluation of lithium secondary battery coin cells according to Example 3 and Comparative Example 3.

[0157] Fig. 9a) is a result of constant current charge / discharge evaluation of a lithium secondary battery coin cell according to Comparative Example 3, and Fig. 9b) is a result of constant current charge / discharge evaluation of a lithium secondary battery coin cell according to Example 3.

[0158] As shown in FIG. 9, there is little difference in the initial 0.1 C discharge capacity of the lithium secondary battery coin cells according to Comparative Example 3 and Example 3, but as the current increases to 5 C, the discharge capacity of the coin cell according to Comparative Example 3 is about 55 mAh / g, but the discharge capacity of the coin cell according to Example 3 is about 135 mAh / g, which indicates that the ion movement resistance of the lithium secondary battery coin cell increases due to a significant amount of dead lithium formed from lithium dendrites on the lithium metal surface of the coin cell according to Comparative Example 3 as the current increases.

[0159] On the other hand, it is shown that MPC, a zwitterionic material present in the electrolyte on the lithium metal surface of the coin cell according to Example 3, forms a polarization field at the lithium metal / electrolyte interface, thereby inducing a uniform lithium ion flux, thereby significantly suppressing lithium dendrites.

[0160] In addition, in a life test conducted at a current of 1 C after a rate test, the discharge capacity of the lithium secondary battery coin cell according to Comparative Example 3 rapidly decreased, whereas the discharge capacity of the lithium secondary battery coin cell according to Example 3 was well maintained. This indicates that the MPC, a zwitterion material present in the electrolyte, formed a polarization field at the lithium metal / electrolyte interface to induce a uniform lithium ion flux, thereby improving the life characteristics of the battery.

[0161] Although the metal oxide transparent substrate and the manufacturing method thereof according to the embodiments of the present invention have been described as specific embodiments, these are merely examples, and the present invention is not limited thereto, and should be construed as having the broadest scope in accordance with the basic idea disclosed in this specification. Those skilled in the art may implement embodiments not specified by combining or replacing the disclosed embodiments, but this also does not exceed the scope of the present invention. In addition, those skilled in the art may easily change or modify the disclosed embodiments based on this specification, and it is clear that such changes or modifications also fall within the scope of the present invention.

Claims

1. In an electrolyte using a high-k dielectric constant zwitterionic material for a secondary battery that utilizes a metal anode material as the cathode, An organic electrolyte comprising an organic solvent and a metal salt; and An electrolyte mixture comprising a zwitterionic compound having a zwitterion and a weight average molecular weight satisfying a range of 100 to 60,000 g / mol; Electrolyte using high-k zwitterionic material.

2. In paragraph 1, The above electrolyte mixture is, Consisting of 90 to 99.5 wt% of the organic electrolyte and 0.5 to 10 wt% of the zwitterionic compound, Electrolyte using high-k zwitterionic material.

3. In paragraph 2, The above organic electrolyte is, The metal salt is dissolved in the organic solvent at a concentration of 1 M to 4 M. Electrolyte using high-k zwitterionic material.

4. In paragraph 3, The above zwitterionic compound is, A first zwitterionic compound comprising a zwitterionic monomer; A second zwitterionic compound derived from the above zwitterionic monomer and polymerized through an initiator; A third zwitterionic compound derived from the above zwitterionic monomer and polymerized and crosslinked through a crosslinking agent and an initiator; and A fourth zwitterionic compound derived from a combination of a cationic monomer and an anionic monomer and polymerized through an initiator; at least one compound selected from among Electrolyte using high-k zwitterionic material.

5. In paragraph 4, The above zwitterionic monomer is, At least one substance selected from the group consisting of 2-Methacryloyloxyethyl phosphorylcholine (MPC), 3-[[2-(Methacryloyloxy)ethyl]dimethylammonio] propoinate, and Sulfobetainemethacrylate, Electrolyte using high-k zwitterionic material.

6. In paragraph 5, The above cationic monomer is, At least one substance selected from the group consisting of METAC, AETMA and AMPTMA ((3-Acrylamidopropyl) trimethylammonium chloride), The above anionic monomer is, At least one substance selected from the group consisting of SPA, SPM (3-Sulfopropyl methacrylate) and AMPA, Electrolyte using high-k zwitterionic material.

7. In paragraph 6, The above zwitterionic compound is, It has a higher dielectric constant value than the above organic solvent, By increasing the dielectric constant of the electrolyte mixture, the interface between the electrolyte and the metal negative electrode material is stabilized. Electrolyte using high-k zwitterionic material.

8. In paragraph 7, The above zwitterionic compound is, By forming a polarized field on the surface of the metal cathode material, the formation of metal dendrites due to biased deposition of metal ions is suppressed. Electrolyte using high-k zwitterionic material.

9. In paragraph 8, The above organic solvent is, Comprising at least one substance selected from the group consisting of ethylene carbonate, diethyl carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Electrolyte using high-k zwitterionic material.

10. In paragraph 9, The above metal salt is, A lithium salt selected from the group consisting of lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N, LiTFSI), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis-perfluoroethylsulfonylimide (Li(C2F5SO2)2N), lithium thiocyanate (LiSCN), lithium triflate (LiCF3SO3), lithium tetrafluoroaluminate (LiAlF4), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2, LiFSI), and mixtures thereof. Electrolyte using high-k zwitterionic material.

11. In paragraph 10, The above cross-linking agent is, Containing any one substance selected from the group consisting of poly(ethyleneglycol) diacrylate and trimetylopropane troacrylate, The above initiator comprises any one substance selected from the group consisting of ammonium persulfate, 2.2'-Azobisisobutylonitrile, Photoinitiator 184, and Photoinitiator 2959. Electrolyte using high-k zwitterionic material.

12. In a method for manufacturing an electrolyte using a high-k zwitterionic material for a secondary battery using a metal cathode material as a cathode, A first step of preparing an organic electrolyte containing an organic solvent and a metal salt; and A second step of preparing an electrolyte mixture by mixing a zwitterionic compound having a weight average molecular weight in the range of 100 to 60,000 g / mol and having a zwitterion into a prepared organic electrolyte; comprising; A method for manufacturing an electrolyte using a high-dielectric constant zwitterionic material.

13. Bipolar; A cathode comprising a metal cathode material; An electrolyte disposed between the anode and the cathode, and using a high-k zwitterionic material according to any one of claims 1 to 8; and A separator positioned on an electrolyte using the high dielectric constant zwitterionic material; including; Secondary battery.

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