Aqueous lithium-ion battery containing highly concentrated lithium salt and zwitterionic polymer

Abstract

Provided is an aqueous lithium-ion battery. The aqueous lithium-ion battery comprises: a positive electrode active material layer; a negative electrode active material layer; and an aqueous electrolyte positioned between the positive electrode active material layer and the negative electrode active material layer. The aqueous electrolyte includes a lithium salt and an aqueous solvent, and the mass of the lithium salt is greater than that of the aqueous solvent. At least one active material layer of the positive electrode active material layer and the negative electrode active material layer includes a zwitterionic polymer.

Description

Aqueous lithium-ion battery containing a highly concentrated lithium salt and an amphoteric polymer

[0001] The present invention relates to a lithium secondary battery, and more specifically to an aqueous lithium secondary battery.

[0002] As portable wireless devices such as mobile phones and portable computers become lighter and more functional, extensive research is being conducted on secondary batteries used as their power sources. Examples of secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium-ion batteries. Among these, lithium-ion batteries are widely used in the field of advanced electronic devices due to their advantages, such as rechargeability, high operating voltage, and high energy density per unit weight.

[0003] The major issues regarding existing lithium-ion batteries include fire safety, environmental impact, cost, and performance. Conventional lithium-ion batteries use organic liquid electrolytes, which are flammable and can lead to thermal runaway and fire risks if the battery is punctured, overcharged, or short-circuited. Furthermore, organic liquid electrolytes are generally based on volatile and toxic solvents, which can cause environmental pollution.

[0004] Accordingly, research on rechargeable batteries utilizing aqueous electrolytes is currently underway. Since aqueous electrolytes are non-flammable, batteries using them are inherently safer and generally more environmentally friendly. Additionally, aqueous electrolytes generally have lower production costs than organic electrolytes, which can reduce the overall cost of the battery. Therefore, aqueous electrolytes can be used in large-scale energy storage and electric vehicle applications where cost is a critical factor. Furthermore, aqueous electrolytes offer higher ionic conductivity than organic electrolytes, allowing for faster charging and discharging speeds. This improves the overall performance of the battery, enabling its application in a wider range of applications.

[0005] However, batteries using aqueous electrolytes have the disadvantage of having to operate within an electrochemical stability window (ESW) where water is not decomposed.

[0006] The technical problem of the present invention is to provide a hydrogel electrolyte capable of expanding the electrochemical stability window and a lithium secondary battery using the same.

[0007] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below.

[0008] To solve the above problem, one aspect of the present invention provides an aqueous lithium-ion battery. The aqueous lithium-ion battery comprises a positive electrode active material layer; a negative electrode active material layer; and an aqueous electrolyte located between the positive electrode active material layer and the negative electrode active material layer. The aqueous electrolyte comprises a lithium salt and an aqueous solvent, wherein the mass of the lithium salt is greater than the mass of the aqueous solvent. At least one of the positive electrode active material layer and the negative electrode active material layer comprises an amphoteric polymer.

[0009] The above-mentioned amphoteric polymer may be a non-crosslinked linear polymer. All monomers included in the above-mentioned amphoteric polymer may be monomers containing amphoteric functional groups. In one example, the above-mentioned amphoteric polymer may be a homopolymer formed by polymerizing identical monomers. The above-mentioned amphoteric polymer may be formed by polymerizing monomers represented by the following chemical formula 1.

[0010] [Chemical Formula 1]

[0011]

[0012] In the above chemical formula 1, R1 is hydrogen or a methyl group, Z is O or NH, m is 0 or 1, L1 and L2 are directly bonded or C1-C4 alkylene groups independently of each other, and either X or Y may be a moiety containing the cationic functional group and the other may be a moiety containing the anionic functional group. X may be a cationic functional group that is ammonium, pyridinium, or pyrazolium, and Y may be an anionic functional group that is a sulfonate or a carboxylate.

[0013] The above-mentioned amphoteric polymer is N-substituted acrylamide sulfobetaine, 1-(3-sulfopropyl)-2-vinylpyridinium hydroxide inner salt, 3-sulfopropyldimethyl-3-methacrylamidopropylammonium inner salt, 1-(4-vinylpyridin-1-ium-1-yl)propane-1-sulfonate, 2-methacryloyloxyethyl phosphorylcholine, The monomer may be polymerized from 3-(1-vinyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonate, carboxybetaine acrylamide, N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine, or a combination of two or more of these. In one example, the amphoteric polymer may be polymerized from N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine.

[0014] In the above aqueous electrolyte, the lithium salt may have a molal concentration of 15 to 35 m.

[0015] The negative electrode active material included in the above negative electrode active material layer may be lithium titanate or Wadsley-Roth niobate. The positive electrode active material included in the above positive electrode active material layer is LiMn (2-x) M xO4 (M can be Ni or Co, 0≤x≤1).

[0016] In one example, at least one active material layer among the positive active material layer and the negative active material layer may include active material particles coated with the amphoteric polymer. In this case, the amphoteric polymer may be contained in an amount of 0.5 to 5 parts by weight per 100 parts by weight of active material particles contained in at least one active material layer among the positive active material layer and the negative active material layer.

[0017] In another example, the two ionic polymers and active material particles may be dispersed and located within at least one of the active material layer and the negative active material layer.

[0018] In another example, the amphoteric polymer may be further included with the aqueous electrolyte between the positive active material layer and the negative active material layer. In this case, when the total weight of the aqueous electrolyte and the amphoteric polymer is 100, the amphoteric polymer may be contained in an amount of 0.04 to 20 parts by weight. The concentration of the amphoteric polymer may decrease from the region adjacent to the positive active material layer or the negative active material layer toward the inner region.

[0019] To solve the above problem, one aspect of the present invention provides a method for manufacturing an aqueous lithium-ion battery. First, a positive electrode comprising a positive active material layer and a negative electrode comprising a negative active material layer are provided. Between the positive electrode and the negative electrode, an aqueous electrolyte comprising a lithium salt and an aqueous solvent, wherein the mass of the lithium salt is greater than the mass of the aqueous solvent, is disposed to assemble the battery. The assembled battery is aged so that the aqueous electrolyte penetrates into the positive active material layer and the negative active material layer, wherein at least one active material layer among the positive active material layer and the negative active material layer in the aged battery comprises monomers having amphoteric functional groups in addition to the aqueous electrolyte. The monomers in the aged battery are polymerized to form an amphoteric polymer within at least one active material layer among the positive active material layer and the negative active material layer.

[0020] The above polymerization can be performed using thermal polymerization or electrochemical polymerization. The above electrochemical polymerization can be performed by conducting a constant current charge-discharge cycle on the assembled battery. The above electrochemical polymerization can be performed by aging the assembled battery in a charged state and then discharging it.

[0021] In one example, in the step of providing the anode and the cathode, at least one active material layer among the anode active material layer and the cathode active material layer may include active material particles coated with the monomers.

[0022] In another example, in the step of providing the anode and the cathode, at least one active material layer among the anode active material layer and the cathode active material layer may be an active material layer in which the monomers and active material particles are mixed.

[0023] In another example, during the step of assembling the battery, a mixture of the aqueous electrolyte and the monomers can be placed between the positive electrode and the negative electrode.

[0024] To solve the above problem, one aspect of the present invention provides a method for manufacturing an aqueous lithium-ion battery. The method for manufacturing an aqueous lithium-ion battery provides a positive electrode comprising a positive active material layer and a negative electrode comprising a negative active material layer, wherein at least one of the positive active material layer and the negative active material layer is an active material layer in which an amphoteric polymer having amphoteric functional groups and active material particles are mixed. Between the positive electrode and the negative electrode, an aqueous electrolyte comprising a lithium salt and an aqueous solvent, wherein the mass of the lithium salt is greater than the mass of the aqueous solvent, is disposed to assemble the battery.

[0025] In the aqueous electrolyte according to the present invention, the mass of the lithium salt is large relative to the mass of the aqueous solvent, so there are almost no free water molecules, making water decomposition difficult, and thus the electrochemical stability window (ESW) can be widened.

[0026] In addition, the aqueous secondary battery according to the present invention comprises an amphoteric polymer or a hydrogel derived therefrom within the negative electrode and / or positive electrode and further within the electrolyte, thereby trapping and preserving water molecules through electrostatic interactions between the amphoteric polymer and water molecules, which can further suppress the generation of free water molecules. Furthermore, the amphoteric polymer can scavenge HF, which may be generated by the reaction of water with the lithium salt containing fluorine, through electrostatic attraction. Accordingly, the stability of the electrolyte and the battery can be further improved.

[0027] FIG. 1 is a schematic diagram showing an aqueous lithium-ion battery according to one embodiment of the present invention.

[0028] Figure 2 shows a DMAPS monomer (a) and its polymer (b).

[0029] Figure 3 shows the Raman spectrum (a) of the DMAPS monomer powder and its polymer, and the FTIR spectrum (b) of the DMAPS monomer powder, its polymer, and the aqueous electrolyte obtained in the preparation example of the aqueous electrolyte.

[0030] FIG. 4 shows the FTIR spectrum (a) for a glass fiber separator containing DMAPS monomer powder, a bare glass microfiber separator used in Example 1 of preparation of an aqueous lithium-ion secondary battery, and a hydrogel electrolyte formed by in situ electrochemical polymerization of DMAPS monomer obtained by decomposing the battery obtained from Example 1 of preparation of a hydrogel electrolyte secondary battery, and the 1500–1850 cm⁻¹ of the FTIR spectrum. -1 Shows the FTIR spectrum (b) with the region magnified.

[0031] FIG. 5 shows a schematic diagram (a) of a hydrogel electrolyte secondary battery prepared in Example 17, comprising a hydrogel electrolyte containing an anode (ZNO), a cathode (LMO), and three DMAPS monomers electrochemically charged and aged hydrogel electrolytes between them, obtained by disassembling the cell before or after main charge-discharge, and an FTIR spectrum (b) of a hydrogel electrolyte secondary battery prepared in Example 17, comprising a hydrogel electrolyte, an anode (ZNO), a cathode (LMO), and three glass fiber separators between them, obtained by disassembling the cell after a pre-charge-discharge cycle and before the main charge-discharge cycle (0 C), after 10 main charge-discharge cycles at 1 C (10 C), and after 300 main charge-discharge cycles (300 C).

[0032] FIG. 6 is a schematic diagram (a) showing glass fiber separators (Q1, Q2, Q3) containing an anode (ZNO), a cathode (LMO), and a hydrogel electrolyte electrochemically charge-aged polymerized from three DMAPS monomers between them, obtained by disassembling the cell prepared in Hydrogel Electrolyte Secondary Battery Preparation Example 17 before or after main charge-discharge; a Raman spectrum (b) for the three glass fiber separators (Q1, Q2, Q3) obtained by disassembling the cell prepared in Hydrogel Electrolyte Secondary Battery Preparation Example 17 before main charge-discharge cycles (0 C); and a Raman spectrum for the three glass fiber separators (Q1, Q2, Q3) obtained by disassembling the cell prepared in Hydrogel Electrolyte Secondary Battery Preparation Example 17 after 10 main charge-discharge cycles at 1 C (10 C) and after 300 main charge-discharge cycles (300 C). Shows the spectrum (c).

[0033] FIG. 7 shows 1C (theoretical capacity 148 mAh g) for a battery (LTO / LMO) according to Preparation Example 1 of an aqueous lithium-ion secondary battery using a pure aqueous electrolyte without the addition of amphoteric ionic monomers such as DMAPS. -1 It shows the voltage profile (a) after performing the initial 2 constant current charge / discharge cycles and the graph (b) showing the change in capacity after performing a total of 100 cycles.

[0034] FIG. 8 shows the battery (ZNO / LMO) according to Preparation Example 2 of an aqueous lithium-ion secondary battery using a pure aqueous electrolyte without the addition of amphoteric ionic monomers such as DMAPS, with 1C (theoretical capacity 148 mAh g -1 It shows the voltage profile (a) after performing the initial 2 constant current charge / discharge cycles and the graph (b) showing the change in capacity after performing a total of 300 cycles.

[0035] FIG. 9 shows a hydrogel electrolyte secondary battery (LTO / LMO) according to Preparation Example 1 using an aqueous electrolyte containing the amphoteric ionic monomer DMAPS, at 1C (theoretical capacity 148 mAh g) during preparation. -1 This shows the voltage profile (a) after performing the initial 2 free constant current charge / discharge cycles at ), and the graph (b) showing the change in capacity when performing a total of 100 constant current charge / discharge cycles at 1C including 2 free constant current charge / discharge cycles.

[0036] FIG. 10 shows a hydrogel electrolyte secondary battery (LTO / LMO) according to Preparation Example 2 using an aqueous electrolyte containing the amphoteric ionic monomer DMAPS, at 1C (theoretical capacity 148 mAh g) during preparation. -1 This shows the voltage profile (a) after performing the initial 2 free constant current charge / discharge cycles at ), and the graph (b) showing the change in capacity when performing a total of 100 constant current charge / discharge cycles at 1C including 2 free constant current charge / discharge cycles.

[0037] FIG. 11 shows a hydrogel electrolyte secondary battery (LTO / LMO) according to Preparation Example 3 using an aqueous electrolyte containing the amphoteric ionic monomer DMAPS, during preparation at 1C (theoretical capacity 148 mAh g). -1 This shows the voltage profile (a) after performing the initial 2 free constant current charge / discharge cycles at ), and the graph (b) showing the change in capacity when performing a total of 100 constant current charge / discharge cycles at 1C including 2 free constant current charge / discharge cycles.

[0038] FIG. 12 shows 1C (theoretical capacity 148 mAh g) for the battery (ZNO / LMO) according to Hydrogel Electrolyte Secondary Battery Preparation Example 6. -1 It shows the voltage profile (a) after performing the initial 2 constant current charge / discharge cycles and the graph (b) showing the change in capacity after performing a total of 300 cycles.

[0039] FIG. 13 shows 1C (theoretical capacity 148 mAh g) for the batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 7 and 8. -1 This shows a graph indicating the change in capacity when a total of 100 constant current charge / discharge cycles were performed.

[0040] FIG. 14 shows 1C (theoretical capacity 148 mAh g) for batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 9 to 11. -1 This shows a graph indicating the change in capacity when a total of 100 constant current charge / discharge cycles were performed.

[0041] FIG. 15 shows 1C (theoretical capacity 148 mAh g) for batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 12 to 13. -1 This shows a graph indicating the change in capacity when a total of 100 constant current charge / discharge cycles were performed.

[0042] FIG. 16 shows 1C (theoretical capacity 148 mAh g) for batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 14 to 16. -1 This shows a graph indicating the change in capacity when a total of 100 constant current charge / discharge cycles were performed.

[0043] FIG. 17 shows the FTIR spectrum (a) for the anode in which the DMAPS monomer was in situ electrochemically polymerized, obtained by disassembling the battery obtained in the secondary battery preparation example having DMAPS monomer powder, the anode (LTO electrode) obtained in Cathode Preparation Example 2, and the DMAPS-coated active material after 1 cycle of pre-charge / discharge or 10 cycles of main charge / discharge, and the 1500–1850 cm⁻¹ of the FTIR spectrum (a). -1 Shows the FTIR spectrum (b) with the region magnified.

[0044] FIG. 18 shows 1C (theoretical capacity 148 mAh g) for a battery (DMAPS-coated LTO / DMAPS-coated LMO) according to an example of secondary battery preparation having a DMAPS-coated active material. -1 The graph (b) shows the voltage profile (a) after performing the initial 2 free constant current charge / discharge cycles and the change in capacity when performing a total of 100 constant current charge / discharge cycles including the free constant current charge / discharge cycles.

[0045] FIG. 19a is the FTIR spectrum for the DMAPS monomer powder, the anode (LTO electrode) obtained in Cathode Preparation Example 2, and the anode (poly DMAPS + LTO) obtained in Cathode Preparation Example 6, and FIG. 19b is the 1500–1850 cm⁻¹ of FIG. 19a. -1 This is an FTIR spectrum with the region magnified.

[0046] FIG. 20 shows a secondary battery according to Manufacturing Example 1 (LTO+DMAPS / LMO+DMAPS) having electrodes including DMAPS, with 1C (theoretical capacity 148 mAh g -1 This shows the voltage profile (a) after performing the initial two free constant current charge / discharge cycles and the graph (b) showing the change in capacity when a total of 100 constant current charge / discharge cycles, including the free constant current charge / discharge cycles, were performed.

[0047] FIG. 21 shows a secondary battery according to Preparation Example 2 (LTO+poly-DMAPS / LMO+poly-DMAPS) having electrodes including DMAPS, with 1C (theoretical capacity 148 mAh g -1 It shows the voltage profile (a) after performing the first two constant current charge / discharge cycles and the graph (b) showing the change in capacity after performing a total of 100 constant current charge / discharge cycles.

[0048] The present invention is susceptible to various modifications and may take various forms; therefore, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0049] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0050] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0051]

[0052] Water-based lithium-ion battery

[0053] FIG. 1 is a schematic diagram showing an aqueous lithium-ion battery according to one embodiment of the present invention.

[0054] Referring to FIG. 1, an aqueous lithium-ion battery (100) may include a negative electrode comprising a negative electrode active material layer (130); a positive electrode comprising a positive electrode active material layer (140); and an aqueous electrolyte (150) disposed between the negative electrode and the positive electrode. The aqueous electrolyte (150) may be impregnated within a separator (not shown).

[0055] The above-mentioned aqueous lithium-ion battery can be assembled in the form of a coin cell, a Swagelok cell, or a pouch cell. However, in the case of a coin cell, the internal negative electrode side is completely covered with an additional Al foil to protect the stainless steel case (Grade 316L) from the electrolyte, and in some cases, the positive electrode side can also be protected with a Ti foil or a Ti disk.

[0056]

[0057] anode

[0058] The positive electrode may include a positive active material layer (140) formed by applying a slurry containing a positive active material, a binder, a conductive material, and a solvent onto a positive current collector (120). Applying the slurry or paste onto the current collector may be performed, for example, using a gravure coating method, a slit die coating method, a knife coating method, or a spray coating method.

[0059] The positive current collector (120) is selected from stainless steel (e.g. 316L grade), titanium, carbon-based material, or a combination thereof, wherein the carbon-based material may be graphite, carbon paper, carbon nanotube paper, carbon cloth, or graphene paper.

[0060] The above-mentioned cathode active material may be a lithium transition metal oxide, a lithium transition metal phosphate, or a transition metal oxide. Specifically, the above-mentioned cathode active material is LiMn (2-x) M x O4 (M is Ni or Co, 0≤x≤1), examples of which are LiMn2O4 (LMO), LiMnCoO4, or LiMn 1.5 Ni 0.5 O4(LMNO); LiM (1-x) Mn x PO4 (M is Fe, Co, or Ni, 0≤x<1), examples of which are LiFePO4(LFP), LiCoPO4, LiNiPO4, or LiFe 0.4 Mn 0.6 PO4(LFMP); Li2MPO4F (M is Co or Ni, 0≤x<1) Examples include Li2CoPO4F or Li2NiPO4F; LiNi x Co y Mn z O2 (0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1), as examples include LiCoO2 or LiNi 0.8 Co 0.1 Mn 0.1 O2; 5,6,11,12-tetraazanaphthacene (TANC); or a combination thereof, may be selected as a material capable of operating within the electrochemical stability window of the battery according to the embodiment.

[0061] The above conductive material is a nano-sized particle that improves the electronic conductivity between active material particles, and can be used without limitation as long as it is generally available in the industry, for example, artificial graphite, natural graphite, carbon black, acetylene black, Super P, Ketjen black, Denka black, thermal black, channel black, carbon nanofiber, carbon nanotube, metal fiber, reduced graphene oxide, or a mixture thereof.

[0062] The above binder may be, for example, polyvinylidene fluoride (PVdF), a copolymer of polyhexafluoropropylene-polyvinylidene fluoride (PVdF / HFP), poly(vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone (PVP), polyvinylpyridine, alkylated polyethylene oxide, polyvinyl ether, poly(methyl methacrylate), poly(ethyl acrylate), polytetrafluoroethylene (PTFE), polyvinyl chloride, polyacrylonitrile (PAN), styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, ethylene-propylene-diene monomer (EPDM), sulfonated ethylene-propylene-diene monomer, carboxymethylcellulose (CMC), sodium carboxymethylcellulose, regenerated cellulose, starch, hydroxypropylcellulose, tetrafluoroethylene, or a mixture thereof. There are. In one example, the binder may be a water-based binder, specifically carboxymethylcellulose (CMC), a mixture of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC), polyacrylic acid, or lithium polyacrylate, but is not limited thereto.

[0063] The solvent may be an organic solvent, specifically N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, etc., when the binder is an organic binder, and a water-based solvent, specifically water, ethanol, isopropyl alcohol (IPA), etc., when the binder is a water-based binder, and these solvents may be used alone or in a mixture of two or more. In one embodiment, the binder may be a water-based binder and the solvent may be water, but is not limited thereto. The amount of the solvent used may be adjusted to an appropriate viscosity capable of dissolving and dispersing the active material, binder, and conductive material, taking into account the coating thickness of the slurry and the manufacturing yield.

[0064] The positive active material layer (140) may be formed on the positive current collector layer (120) with a thickness of 50 to 200 μm, specifically with a thickness of 100 to 150 μm, but is not limited thereto.

[0065]

[0066] cathode

[0067] The cathode may include a cathode active material layer (130) formed by applying a slurry containing a cathode active material, a binder, a conductive material, and a solvent onto a cathode current collector (110). Applying the slurry or paste onto the current collector may be performed, for example, using a gravure coating method, a slit die coating method, a knife coating method, or a spray coating method.

[0068] The above-mentioned negative current collector (110) is selected from aluminum, titanium, carbon-based materials, or a combination thereof, wherein the carbon-based material may be graphite, carbon paper, carbon nanotube paper, carbon cloth, or graphene paper. In one example, the above-mentioned negative current collector (110) may be graphene-coated aluminum or carbon-coated aluminum.

[0069] The above-mentioned negative electrode active material is a Wadsley-Roth niobate-based material having a Wadsley-Roth phase composed of blocks formed by ReO3-type metal-oxygen octahedrons sharing edges, specifically Zn2Nb 34 O 87 , In 0.5 Nb 24.5 O 62 , InNb 11 O 29 ; Lithium titanate, specifically, Li4Ti5O 12 (LTO); Mo6S8, TiO2, MoS2, MoO3, Li (3+x) V2O5(x is 0 to 0.5), Li x Nb 2 / 7 Mo 3 / 7 O2(x is 0 to 1), LiTi2(PO4)3, VO 2 ,MXene (ex. M x X y , M = Ti, Mo, Nb, X = N, C, x is 2 to 4, y is 1 to 3), PTCDI (perylene-3,4,9,10-tetracarboxylic acid diimide) or a combination thereof, selected from a material capable of operating within the electrochemical stability window of the battery according to the example.

[0070] The above conductive material may be used without restriction as long as it is generally available in the industry, and specific examples have been described in the anode section.

[0071] Specific examples of the binder above have been described in the anode section, and like the anode, it may be a water-based binder, and specifically, a mixture of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC) or lithium polyacrylate may be used, but is not limited thereto.

[0072] Specific examples of the above solvent were described in the cathode section, and when the binder is an aqueous binder, the solvent may be water, but is not limited thereto.

[0073] The above negative electrode active material layer (130) may be formed on the negative electrode current collector (110) with a thickness of 50 to 200 μm, specifically with a thickness of 100 to 150 μm, but is not limited thereto.

[0074]

[0075] Separator

[0076] The separator may be an insulating porous support or a fiber support, as an example, a fiber fabric in which fibers are arranged in the form of a woven or nonwoven fabric, specifically a fiber glass subatrate or a glass microfiber support.

[0077]

[0078] aqueous electrolytes

[0079] The above aqueous electrolyte (150) may include a lithium salt and an aqueous solvent.

[0080] The above lithium salt is Li a X b It can be represented as follows. The above X is an anion, Cl - , Br - , I - , SO4 2- , NO3 - , ClO4 - , OH - , RSO3 - , RCOO - , (R1SO2)(R2SO2)N - , or (SO2R3SO2)N - It may be. Here, each of R, R1, and R2 may be fluorine, a C1 to C4 alkyl, a C1 to C4 fluoroalkyl, or a C1 to C4 perfluoroalkyl. R3 may be a C1 to C4 alkylene, a C1 to C4 fluoroalkylene, or a C1 to C4 perfluoroalkylene. In one example, X is RSO3 - , (R1SO2)(R2SO2)N - , or (SO2R3SO2)N - It may be, and each of R, R1, and R2 may be fluorine or a C1 to C4 perfluoroalkyl, and R3 may be a C1 to C4 perfluoroalkylene. In this case, the anion may be oxidized or reduced to form a solid electrolyte interphase (SEI) on the surface of the anode or cathode, and in this case, water splitting may be further suppressed. a and b are integers selected so that the lithium salt may exhibit charge neutrality, b may be 1, and a may be 1 or 2.

[0081] The lithium salt is specifically, LiCl (lithium chloride), Li2SO4 (lithium sulfate), LiNO3 (lithium nitrate), LiClO4 (lithium perchlorate), LiOH (lithium hydroxide), LiOOCCH3 (lithium acetate), LiCF3SO3 (lithium trifluoromethanesulfonate, LiOTF), LiN (SO2CF3)2 (lithium bis) (trifluoromethanesulfonyl) imide, LiTFSI), LiN(SO2CH3)2, LiN(SO2C4H9)2(Lithium bis(butylsulfonyl)imide), LiN(SO2C2F5)2(lithium bis (pentafluoroethanesulfonyl) imide, LiBETI), LiN(SO2C4F9)2, LiN(SO2CF3)(SO2C4F9), LiN(SO2C2F5)(SO2C4F9), LiN(SO2C2F4SO2), It may include one or more selected from the group consisting of LiN(SO2F)2 and LiN(SO2F)(SO2CF3).

[0082] In one example, the lithium salt is such that X is (R1SO2)(R2SO2)N - It may include LiN(SO2R1)(SO2R2). In this case, R1 and R2 may each be a C1 to C2 perfluoroalkyl. The lithium salt is X in RSO3 - It may additionally include LiSO3R. In this case, R may be a C1 to C2 perfluoroalkyl. In another example, the lithium salt may include two different types, namely a first LiN(SO2R1)(SO2R2) and a second LiN(SO2R1)(SO2R2), wherein each of R1 and R2 is a C1 to C2 perfluoroalkyl, and the first LiN(SO2R1)(SO2R2) and the second LiN(SO2R1)(SO2R2) may be selected to be different from each other.

[0083] The above aqueous solvent may be water. In one example, the above aqueous solvent may consist only of water. However, it is not limited thereto, and in some cases, the above aqueous electrolyte may contain a small amount of an organic solvent as an additive, for example, 0.1 to 60 wt%, specifically 0.5 to 5 wt%. The above organic solvent may be a carbonate-based solvent, sulfolane, or ether-based solvent. The carbonate-based solvent may be DMC (dimethyl carbonate), FEC (fluoroethylene carbonate), VC (vinyl carbonate), EC (ethylene carbonate), EMC (ethyl methyl carbonate), PC (propylene carbonate), DEC (diethyl carbonate), VEC (vinyl ethylene carbonate), or a combination of two or more of these. The ether-based solvent may be a hydrofluoroether (HFE) as an example.

[0084] The above-mentioned aqueous electrolyte (150) may be a superconcentrated electrolytic solution. In this case, the superconcentrated electrolyte may be a water-in-salt electrolyte, or furthermore a hydrate melt electrolyte, in which the mass and volume of the lithium salt are greater than that of the aqueous solvent. In the water-in-salt electrolyte, almost all solvent molecules coordinate with cations derived from the lithium salt to form cation solvation spheres, so that there may be almost no free water molecules. Furthermore, the hydrate melt electrolyte contains a higher concentration of salt than the water-in-salt electrolyte, meaning that the salt is not dissolved in water, but rather the water molecules are in a state similar to 'hydrate' contained within the crystal structure of the salt, and for this reason, it means that it exhibits properties similar to 'melt' which is in a liquid state at room temperature. In such highly concentrated electrolytes, there are almost no free water molecules, making water splitting difficult, so the electrochemical stability window (ESW) can be widened. In addition, hydrate molten electrolytes have a high lithium ion transfer rate, so high capacity can be achieved even at high current rates.

[0085] In one example, the lithium salt may be in a saturated or supersaturated state within the aqueous electrolyte. When two or more lithium salts are used, saturation or supersaturation may occur at a higher total concentration compared to when only one lithium salt is used. Additionally, when two or more different types of lithium salts are used, the lithium salts may have a compositional ratio that results in a eutectic composition so that they can be dissolved at a maximum concentration.

[0086] The lithium salt may have a concentration of more than 7 m (molality, mol / kg) and less than or equal to 50 m, 10 to 40 m, 15 to 35 m, 20 to 33 m, or 25 to 30 m. In one embodiment, the lithium salt may include LiTFSI as an example of a first LiN(SO2R1)(SO2R2) of 13 to 30 m, specifically 15 to 25 m, more specifically 18 to 22 m, and LiBETI as an example of a second LiN(SO2R1)(SO2R2) of a different type from the first LiN(SO2R1)(SO2R2) of 5 to 10 m, specifically 8 to 9 m. The molal concentration of the first LiN(SO2R1)(SO2R2) may be greater than the molal concentration of the second LiN(SO2R1)(SO2R2). Specifically, the molal concentration of the first LiN(SO2R1)(SO2R2) may be 2 to 3 times greater than the molal concentration of the second LiN(SO2R1)(SO2R2). The number of carbon atoms in at least one of R1 and R2 in the first LiN(SO2R1)(SO2R2) may be smaller than the number of carbon atoms in at least one of R1 and R2 in the second LiN(SO2R1)(SO2R2). Water in the aqueous electrolyte may have a concentration of 6 wt% or more or 60,000 ppm or more, but may have a concentration of 12 wt% or less.

[0087]

[0088] A water-based secondary battery (100) according to one embodiment of the present invention may include a zwitterionic polymer in the negative electrode, specifically the negative electrode active material layer (130) and / or the positive electrode, specifically the positive electrode active material layer (140). Furthermore, the water-based secondary battery (100) may also include a zwitterionic polymer in the water-based electrolyte (150).

[0089] The above-mentioned amphoteric polymer is a polymer containing amphoteric functional groups in its side chains and may be a non-crosslinked linear polymer. Since the amphoteric polymer contains both positive and negative charges within the same molecule and exhibits a high zeta potential, it repels each other and does not aggregate; however, it can form a hydrogel by forming a strong hydration layer through electrostatic interactions with water molecules in an aqueous electrolyte absorbed into the cathode and / or anode, thereby trapping and preserving water molecules. Accordingly, the hydrogel may include the amphoteric polymer and an aqueous electrolyte bonded to or impregnated therewith through electrostatic interactions. As a result, the generation of free water molecules can be suppressed. Consequently, the electrochemical stability of the aqueous solvent used in the aqueous electrolyte, e.g., water, can be improved, thereby widening the electrochemical stability window (ESW) of the battery.

[0090] In addition, when lithium ions are inserted into the electrode during the battery's charge-discharge cycle, decomposition products of water molecules accumulate at the electrode-electrolyte interface and react with fluorine-containing anions of the lithium salt to produce HF as a byproduct. However, the amphoteric polymer forms a strong hydration layer to effectively capture water molecules, thereby preventing their decomposition. Consequently, it prevents the decomposed water molecules from reacting with anions to form hydrofluoric acid (HF). Furthermore, even if HF is generated, the amphoteric functional groups can scavenge the generated HF through electrostatic attraction. As a result, electrolyte and battery stability can be further improved.

[0091] Thanks to this extended stability range, a wider variety of electrodes can be used, and Li4Ti5O as the negative electrode active material 12 It contains LiMn2O4 as the positive electrode active material and has a cutoff voltage of 2.8 V, or Zn2Nb as the negative electrode active material. 34 O 87A high-voltage aqueous secondary battery having a cutoff voltage of 2.75 V can be realized by including LiMn2O4 (ZNO) as the positive active material.

[0092] As such, a secondary battery according to one embodiment of the present invention may include an amphoteric polymer or a hydrogel derived therefrom within the negative electrode and / or positive electrode, and further within the aqueous electrolyte (150).

[0093]

[0094] In the first embodiment, the amphoteric polymer or hydrogel based thereon may coat the negative active material particles in the negative electrode and / or the positive active material particles in the positive electrode. In other words, the amphoteric polymer layer or the hydrogel layer based thereon may be disposed on the surface of the active material particles. The active material particles and the amphoteric polymer layer or the hydrogel layer based thereon may have a core-shell structure. In one example, the monomer(s) constituting the amphoteric polymer may remain unpolymerized along with the amphoteric polymer within the shell. In this embodiment, the amphoteric polymer may be disposed exclusively within the shell and may not be dispersed within the electrodes or within the electrolyte.

[0095] In the second embodiment, the amphoteric polymer or the hydrogel based thereon may be dispersed within the negative active material layer in the cathode and / or the positive active material layer in the anode. In other words, the amphoteric polymer or the hydrogel based thereon may be dispersed together with a binder within the negative active material layer in the cathode and / or the positive active material layer in the anode. In one example, the monomer(s) constituting the amphoteric polymer may remain unpolymerized along with the amphoteric polymer within the negative active material layer and / or the positive active material layer. In this embodiment, the amphoteric polymer may be exclusively disposed within the electrode, specifically within the electrode active material layer, and may not be dispersed within the electrolyte.

[0096] In the third embodiment, the amphoteric polymer may impregnate an aqueous electrolyte between the anode and the cathode to form a hydrogel electrolyte. In this case, the amphoteric polymer or the hydrogel based thereon may be located within the pores of the separator described above. However, even in this case, the amphoteric polymer may be dispersed and located within the anode and the cathode as in the second embodiment described above. In one example, the monomer(s) constituting the amphoteric polymer may remain in the hydrogel electrolyte without polymerizing along with the amphoteric polymer.

[0097] All monomers included in the above-mentioned amphoteric polymer may be the same or different monomers that have amphoteric functional groups in their side chains. In one example, the polymer may be a homopolymer formed by polymerizing identical monomers that have amphoteric functional groups in their side chains.

[0098] The above monomer may have polymerizable functional groups within its molecular structure, specifically polymerizable functional groups capable of radical polymerization, more specifically vinyl polymerizable functional groups. As an example, the vinyl polymerizable functional group may include at least one of the following: a vinyl group, an allyl group, an acrylate group, a methacrylate group, an acrylamide group, or a methacrylamide group. Accordingly, the backbone of the polymer may be polyvinyl, polyallyl, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, or a copolymer thereof. The polymer may be a polymer having a linear structure.

[0099] The above zwitterionic group can be directly or indirectly bonded to the polymerizable functional group of the monomer and to the polymer backbone. In this case, the polymerizable functional group and the zwitterionic functional group may be directly bonded or connected or indirectly bonded via C1-C4 alkylene groups. The zwitterionic functional group possesses both cationic and anionic functional groups, signifying an electrically neutral motif, and can absorb and adsorb water molecules through strong electrostatic attraction relative to hydrogen bonding. The above cationic functional group is ammonium (e.g., -Y1Y2N + - or Y1Y2Y3N + -, where Y1, Y2, and Y3 are C1-C2 alkyl groups independent of each other), pyridinium (ex. -C5H4N + - or C5H5N + -), or it may be pyrazolium, and the anionic functional group is a sulfonate (e.g., -SO3 - ), carboxylate (ex. -COO - ), or phosphate (phosphate, ex. -OP(=O)[O -It may be ]O-). The cationic functional group and the anionic functional group may be connected by a C1-C4 alkylene group. However, it is not limited thereto.

[0100] The above monomer may be a monomer represented by the following chemical formula 1, and the above polymer may be a polymer represented by the following chemical formula 2.

[0101] [Chemical Formula 1]

[0102]

[0103] In the above chemical formula 1, R1 may be hydrogen or a methyl group, Z may be O or NH, m may be 0 or 1, L1 and L2 may be directly bonded or C1-C4 alkylene groups independently of each other, and either X or Y may be a moiety containing the cationic functional group and the other may be a moiety containing the anionic functional group.

[0104] [Chemical Formula 2]

[0105]

[0106] In the above chemical formula 2, R1 may be hydrogen or a methyl group, Z may be O or NH, m may be 0 or 1, L1 and L2 may be directly bonded or C1-C4 alkylene groups independently of each other, and either X or Y may be a moiety containing the cationic functional group and the other may be a moiety containing the anionic functional group. Additionally, n may be 10 to 100.

[0107] In the above Chemical Formulas 1 and 2, X is a cationic functional group of ammonium (e.g., -Y1Y2N + -, where Y1 and Y2 are C1-C2 alkyl groups independent of each other), pyridinium (ex. -C5H4N + - or C5H5N + -), or it can be pyrazolium, and Y is an anionic functional group, sulfonate (e.g., -SO3- ) or carboxylate (e.g., -COO - It may be ). In another example, in the above Chemical Formulas 1 and 2, X is an anionic functional group phosphate (ex. -OP(=O)[O - It can be ]O-), and Y is a cationic functional group Y1Y2Y3N + - (Here, Y1, Y2, and Y3 are C1-C2 alkyl groups independent of each other) may be.

[0108]

[0109] The above monomers are, as examples, N-substituted acrylamide sulfobetaine, 1-(3-sulfopropyl)-2-vinylpyridinium hydroxide inner salt, 3-sulfopropyldimethyl-3-methacrylamidopropylammonium inner salt, 1-(4-vinylpyridin-1-ium-1-yl)propane-1-sulfonate, 2-methacryloyloxyethyl phosphorylcholine, 3-(1-vinyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonate, carboxybetaine acrylamide, N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (or [2-(Methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide, DMAPS), or a combination of two or more of these may be included. In one example, the first monomer is a sulfonate (-SO3 - ) and ammonium (-Y1Y2N + -, where Y1 and Y2 may be DMAPS containing a methyl group as a zwitterionic motif. FIG. 2a shows a DMAPS monomer and FIG. 2b shows a polymer thereof.

[0110] These monomers can be polymerized by methods such as free radical polymerization or electropolymerization, such as UV polymerization or thermal polymerization, to form the aforementioned amphoteric polymer. In one example, the monomers may undergo "in-situ polymerization." Here, "in-situ polymerization" means that the polymerization process proceeds directly inside the battery before or during operation after battery assembly. In-situ polymerization can be induced thermally or electrochemically.

[0111]

[0112] Manufacturing of an aqueous lithium-ion battery according to the first embodiment

[0113] The first embodiment described above, that is, coating the negative active material particles in the negative electrode and / or the positive active material particles in the positive electrode with the amphoteric polymer or a hydrogel based thereon, can be implemented in the following manner. Below, the negative active material and the positive active material are referred to as electrode active materials without distinction, and the negative electrode and the positive electrode are referred to as electrodes without distinction.

[0114] First, an amphoteric monomer is dissolved in a solvent to obtain an amphoteric monomer solution, and electrode active material particles are added to this amphoteric monomer solution. Then, the solvent is evaporated and further dried to remove residual moisture, thereby obtaining electrode active material particles coated with the amphoteric monomer. At this time, the solvent may be a dry alcohol, specifically dry ethanol. For every 100 parts by weight of the electrode active material particles coated with the amphoteric monomer, the amphoteric monomer may be contained in an amount of 0.5 to 5 parts by weight, specifically 1 to 3 parts by weight, as an example, 2 parts by weight.

[0115] Afterward, electrode active material particles coated with both ionic monomers are mixed with the aforementioned binder, conductive material, and solvent to form a slurry, and then coated onto a current collector (110 and / or 120 in FIG. 1) to prepare electrodes, i.e., a positive electrode and a negative electrode, comprising an electrode active material layer (130 and / or 140 in FIG. 1). After placing the aforementioned separator between the prepared positive electrode and the negative electrode, the aforementioned aqueous electrolyte (150 in FIG. 1) is infiltrated to assemble the battery.

[0116] After assembling the battery, the battery may be aged for several hours so that the aqueous electrolyte can sufficiently penetrate into the positive active material layer and the negative active material layer to achieve equilibrium. Subsequently, a free constant current charge-discharge cycle may be performed on the aged battery to in situ electrochemical polymerization of the amphoteric monomers coated on the electrode active material particles, thereby forming an amphoteric polymer shell or a hydrogel shell based thereon. In this case, the amphoteric polymer may remain on the surface of the electrode active material particles, and the electrolyte may remain in a liquid state. In this specification, the free constant current charge-discharge cycle is for polymerizing the amphoteric monomers within the battery and may be performed during the battery formation process.

[0117] In this way, when electrode active material particles are coated with an amphoteric polymer, a uniform polymer layer can be formed on the electrode particles without changing the viscosity of the electrolyte, and the stability of the electrode and ion transport at the electrode-electrolyte interface can be improved. Specifically, the amphoteric polymer is located between the electrode active material particles and the aqueous electrolyte interface and can combine with hydrofluoric acid (HF), thereby preventing corrosion of the electrode active material by HF, which can improve the stability of the electrode and extend the electrode life.

[0118] An example of manufacturing a water-based lithium-ion battery according to the first embodiment can be seen in the example of manufacturing a secondary battery having a DMAPS-coated active material described below.

[0119]

[0120] Manufacturing of an aqueous lithium-ion battery according to the second embodiment

[0121] The above second embodiment, i.e., the amphoteric polymer or hydrogel based thereon, can be implemented in the following way when dispersed in the negative active material layer within the negative electrode and / or the positive active material layer within the positive electrode. Below, the negative active material and the positive active material are not distinguished and are referred to as electrode active materials, and the negative electrode and the positive electrode are not distinguished and are referred to as electrodes.

[0122] First, an electrode slurry in which an amphoteric monomer is dispersed can be prepared. Specifically, an amphoteric monomer-binder mixture can be obtained by placing the amphoteric monomer into a binder dispersion, specifically a binder dispersion containing a binder polymer and a solvent, and mixing them. In one example, the binder dispersion may be an aqueous dispersion of an aqueous binder, and in another example, the binder dispersion may be an organic binder dispersed in an organic solvent. The aqueous binder, the organic binder, and the organic solvent have been described above.

[0123] The amphoteric monomer may be contained in an amount of about 0.5% to 5% by weight within the amphoteric monomer-binder mixture. The electrode slurry can be prepared by adding electrode active material particles and a conductive material to the amphoteric monomer-binder mixture and mixing them. The electrode slurry can be coated onto a current collector (110 and / or 120 in FIG. 1) to prepare an electrode, i.e., a positive electrode and a negative electrode, comprising an electrode active material layer (130 and / or 140 in FIG. 1). After placing the separator described above between the prepared positive and negative electrodes, the battery can be assembled by infiltrating the aqueous electrolyte described above (150 in FIG. 1).

[0124] After assembling the battery, the battery may be aged for several hours so that the aqueous electrolyte can sufficiently penetrate into the positive electrode active material layer and the negative electrode active material layer to achieve equilibrium. Subsequently, a constant current charge-discharge cycle may be performed on the aged battery to in situ electrochemical polymerize the amphoteric monomers dispersed within the electrode active material layer of the electrode, thereby allowing an amphoteric polymer or a hydrogel based thereon to be dispersed within the electrode active material layer. An example of manufacturing an aqueous lithium-ion battery according to this method can be seen in Example 1 of manufacturing a secondary battery having electrodes including DMAPS, which will be described later.

[0125] In another example, an electrode slurry in which an amphoteric polymer is dispersed can be prepared. Specifically, a radical initiator is added to a binder dispersion along with an amphoteric monomer and mixed, and then heat is applied while stirring the mixture. The thermocatalyzed radical initiator initiates radical chain polymerization of the amphoteric monomer, and accordingly, the amphoteric monomer is polymerized to form an amphoteric polymer. In the dispersion in which the binder is dispersed along with the amphoteric polymer, the amphoteric polymer may be contained in an amount of about 0.5 wt% to 5 wt%, specifically 2 to 4 wt%. The radical initiator may be a water-soluble or oil-soluble electrolyte salt, such as a persulfate, peroxide, azobis compound, etc. The above electrolyte salt may be at least one selected from persulfates, for example, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, t-butylhydroperoxide, t-butylperoxybenzoate, 2,2-azobis(isobutyronitrile), 2,2-azobis(2-diaminopropane)hydrochloride, and 2,2-azobis(2,4-dimethylvaleronitrile). Specifically, the radical initiator may be at least one selected from potassium persulfate, sodium persulfate, and ammonium persulfate. In one embodiment, the catalyst may be potassium persulfate (K2S2O8), but is not limited thereto. The radical initiator may be used in a range of 0.5% to 5% by weight relative to the amphoteric ion monomer content.

[0126] Afterward, the electrode slurry can be prepared by adding electrode active material particles and a conductive material into a dispersion in which a binder is dispersed together with both ionic polymers and mixing them. The electrode slurry can be coated onto a current collector (110 and / or 120 in FIG. 1) to prepare an electrode, i.e., a positive electrode and a negative electrode, comprising an electrode active material layer (130 and / or 140 in FIG. 1). After placing the separator described above between the prepared positive and negative electrodes, the battery can be assembled by infiltrating the aqueous electrolyte described above (150 in FIG. 1). An example of manufacturing an aqueous lithium-ion battery according to this can be seen in Example 2 of manufacturing a secondary battery having electrodes including DMAPS, which is described later.

[0127] In this way, when the above-mentioned amphoteric polymer or a hydrogel based thereon is dispersed within the negative electrode active material layer in the negative electrode and / or the positive electrode active material layer in the positive electrode, the viscosity of the electrolyte may not change, and the stability of the electrode at the electrode-electrolyte interface and ion transport may be improved. Specifically, the amphoteric polymer can be located between the electrode active material layer and the aqueous electrolyte interface and combine with hydrofluoric acid (HF), thereby preventing corrosion of the electrode active material by HF, which can improve the stability of the electrode and extend the electrode life.

[0128]

[0129] Manufacturing of an aqueous lithium-ion battery according to the third embodiment

[0130] The third embodiment above, that is, the case where an amphoteric polymer impregnates an aqueous electrolyte between the anode and the cathode to form a hydrogel electrolyte, can be implemented in the following way.

[0131] After adding an amphoteric monomer to the above-mentioned aqueous electrolyte, a separator is placed between the anode and the cathode—specifically, between the anode and the cathode that do not contain the amphoteric monomer—and then the aqueous electrolyte containing the amphoteric monomer is infiltrated to assemble a battery. At this time, when the total weight of the aqueous electrolyte and the amphoteric monomer is 100, the amphoteric monomer may be contained in an amount of 0.04 to 20 parts by weight, or in one example, 3 to 7 parts by weight.

[0132] After assembling the battery, the battery may be aged for several hours so that the aqueous electrolyte can sufficiently penetrate into the positive active material layer and the negative active material layer to achieve equilibrium. During this process, the amphoteric monomers in the aqueous electrolyte can coat the surfaces of all particles in the positive electrode, specifically the positive active material particles and the conductive material particles, along with the aqueous electrolyte, and can also be dispersed within a binder matrix located between them, and can also coat the surfaces of all particles in the negative electrode, specifically the negative active material particles and the conductive material particles, and can also be dispersed within a binder matrix located between them.

[0133] In one example, an amphoteric monomer can be in situ electrochemically polymerized by performing a constant current charge-discharge cycle on an aged battery. In this case, electrons transferred from the anode and cathode during the charge-discharge process can generate reactive radical species, which can induce polymer chain propagation and polymer growth. Therefore, electrochemical polymerization begins at the electrode surface and continues throughout the electrolyte; however, the polymerization rate may be slow because multiple charge-discharge cycles are required to achieve complete polymerization, as the mobility of monomers and radical species is reduced due to the high viscosity of the aqueous electrolyte with a very high salt concentration. Specifically, the amphoteric monomer within the anode and cathode active material layers may polymerize first to form an amphoteric polymer, and subsequently, the amphoteric monomer within the electrolyte adjacent to the anode and cathode may polymerize to form an amphoteric polymer, while the amphoteric monomer within the electrolyte not adjacent to the anode and cathode may polymerize last to form an amphoteric polymer. Accordingly, in the initial stage of performing a constant current charge-discharge cycle, specifically after about 10 constant current charge-discharge cycles have been performed, the concentration of the amphoteric polymer in the electrolyte may decrease as it moves from the region adjacent to the anode and cathode to the inner region far from the anode and cathode, while conversely, the concentration of the amphoteric monomer in the electrolyte may increase as it moves from the region adjacent to the anode and cathode to the inner region far from the anode and cathode. However, when the constant current charge-discharge cycle has been sufficiently performed, specifically after about 40 cycles, the concentration of the amphoteric polymer may appear evenly distributed across all regions of the battery (Figs. 3 and 4 thereof).

[0134] For the above-mentioned in-situ electrochemical polymerization, a free constant current charge-discharge cycle may be performed immediately on the aged battery, or electrochemical charge-aging polymerization may be performed by performing a charge-aging charge-discharge cycle in which the aged battery is initially charged, aged for several days in a charged state, and then discharged, followed by a constant current charge-discharge cycle. An example of the manufacture of an aqueous lithium-ion battery in which a free constant current charge-discharge cycle is performed immediately on the aged battery can be seen in Examples 1 to 5 of the manufacture of hydrogel electrolyte secondary batteries described below, and an example of the manufacture of an aqueous lithium-ion battery in which electrochemical charge-aging polymerization is performed can be seen in Example 6 of the manufacture of hydrogel electrolyte secondary batteries described below.

[0135] In another example, heat can be applied to an aged battery to thermally polymerize the amphoteric monomer. To do this, battery assembly and aging can be carried out with a radical initiator added along with the amphoteric monomer in the aqueous electrolyte. During the heating process for thermal polymerization, the thermally catalyzed radical initiator can polymerize the monomer into radical chains. Thermal polymerization can be performed for 1 to 10 hours, specifically 2 to 8 hours, and more specifically 4 to 6 hours, under temperature conditions of 50 to 95°C, specifically 55 to 90°C, more specifically 70 to 85°C. The radical initiator may be a water-soluble or oil-soluble electrolyte salt, such as a persulfate, peroxide, or azobis compound. The above electrolyte salt may be at least one selected from persulfates, for example, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, t-butylhydroperoxide, t-butylperoxybenzoate, 2,2-azobis(isobutyronitrile), 2,2-azobis(2-diaminopropane)hydrochloride, and 2,2-azobis(2,4-dimethylvaleronitrile). Specifically, the radical initiator may be at least one selected from potassium persulfate, sodium persulfate, and ammonium persulfate. In one embodiment, the catalyst may be potassium persulfate (K2S2O8), but is not limited thereto. The radical initiator may be used in a range of 0.5% to 5% by weight relative to the amphoteric ion monomer content.

[0136] Zionic polymers on the electrode surface and within the electrolyte inhibit water splitting by restricting water movement to the electrode surface, and at the electrolyte-electrode interface, zionic polymers interact with and effectively bind to the generated hydrofluoric acid (HF) to improve battery durability.

[0137]

[0138] In the above embodiments, the polymerization of the zwitterionic monomer can be confirmed through Fourier Transform Infrared Spectroscopy (FTIR) analysis or Raman spectroscopy. Specifically, the polymerization of the zwitterionic monomer is confirmed in FTIR analysis at 1715–1730 cm⁻¹. -1 This can be confirmed through a significant decrease in the carbon-carbon double bond peak intensity, and also in Raman spectroscopy at 1635 cm⁻¹. -1 This can be confirmed through a significant decrease in the intensity of the carbon-carbon double bond peak appearing in the vicinity.

[0139]

[0140] The manufacturing of an aqueous lithium-ion battery according to the first and third embodiments above comprises, in common, the step of providing a positive electrode including a positive active material layer and a negative electrode including a negative active material layer; the step of assembling a battery by placing an aqueous electrolyte between the positive electrode and the negative electrode, wherein the aqueous electrolyte comprises a lithium salt and an aqueous solvent, and the mass of the lithium salt is greater than the mass of the aqueous solvent; and the step of aging the assembled battery so that the aqueous electrolyte penetrates into the positive active material layer and the negative active material layer, wherein at least one active material layer among the positive active material layer and the negative active material layer in the aged battery may include monomers having amphoteric functional groups in addition to the aqueous electrolyte. The monomers in the aged battery may be polymerized to form an amphoteric polymer within at least one active material layer among the positive active material layer and the negative active material layer.

[0141] The above polymerization can be performed using thermal polymerization or electrochemical polymerization. The electrochemical polymerization can be performed by conducting a constant current charge-discharge cycle on the assembled battery. Furthermore, the electrochemical polymerization can be performed by aging the assembled battery in a charged state and then discharging it. Each polymerization method may be referenced from the examples described above.

[0142]

[0143] Hereinafter, in order to explain the present invention more specifically, preferred experimental examples according to the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

[0144]

[0145] Aqueous electrolyte preparation example

[0146] A hydrate melt electrolyte was formed by dissolving 1.1389 g of LiN(SO2CF3)2(LiTFSi) (19.44 mol / kg) and 0.6581 g of LiN(SO2C2F5)2(LiBETi) (8.33 mol / kg) in 0.2 ml of ultrapure water. Dissolution was performed by mixing for 10 minutes at 2000 RPM (Revolutions Per Minute) in a Thinky mixer using a 40 mL container containing 5 mm alumina balls. The prepared electrolyte was stored in a dry place.

[0147]

[0148] Examples of preparation of monomer-electrolyte solutions 1 to 3

[0149] A monomer-electrolyte solution was prepared by adding DMAPS ([2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide) monomer to the aqueous electrolyte obtained in the aqueous electrolyte preparation example, such that the weight ratio of the aqueous electrolyte to DMAPS was 97:3 (Preparation Example 1), 95:5 (Preparation Example 2), or 93:7 (Preparation Example 3), and then mixing at 2000 RPM for 10 minutes in a Thinky mixer.

[0150]

[0151] Examples of preparing monomer-electrolyte solutions 4 to 6

[0152] A monomer-electrolyte solution was prepared by adding a potassium persulfate (KPS) radical initiator to the aqueous electrolyte obtained in the aqueous electrolyte preparation example, wherein the weight ratio of the aqueous electrolyte to the DMAPS was 95:5 (Preparation Example 4), 90:10 (Preparation Example 5), or 85:15 (Preparation Example 6), and the ratio of KPS to the weight of DMAPS was 2 wt%, and then mixing at 2000 RPM for 10 minutes in a Thinky mixer.

[0153]

[0154] Examples of preparing monomer-electrolyte solutions 7 to 8

[0155] A monomer-electrolyte solution was prepared by adding a DMAPS monomer, an acrylamide (AAm) monomer, an N,N-methylenebisacrylamide (MBA) crosslinking agent, and a KPS radical initiator to the aqueous electrolyte obtained in Preparation Example 1, wherein the weight ratio of the aqueous electrolyte, the DMAPS monomer, and the AAm monomer was 95:0.25:4.75 (Preparation Example 7) or 90:0.5:9.5 (Preparation Example 8), and the MBA crosslinking agent was at a ratio of 0.5 wt% and the KPS at a ratio of 2 wt% relative to the total weight of the DMAPS and AAm monomers, and then mixing at 2000 RPM for 10 minutes in a Thinky mixer.

[0156]

[0157] Examples of preparation of monomer-electrolyte solutions 9 to 11

[0158] A monomer-electrolyte solution was prepared by adding a monomer DMAPS, an monomer AAm, and a radical initiator KPS to the aqueous electrolyte obtained in Preparation Example 1, wherein the weight ratio of the aqueous electrolyte, the monomer DMAPS, and the monomer AAm was 90:2.5:7.5 (Preparation Example 9), 90:5:5 (Preparation Example 10), or 90:7.5:2.5 (Preparation Example 11), and the KPS was at a ratio of 2 wt% to the total weight of the monomers DMAPS and AAm, and then mixing at 2000 RPM for 10 minutes in a Thinky mixer.

[0159]

[0160] Examples of preparation of monomer-electrolyte solutions 12 to 13

[0161] A monomer-electrolyte solution was prepared by adding a DMAPS monomer, an MBA crosslinking agent, and a KPS radical initiator to the aqueous electrolyte obtained in Preparation Example 1, wherein the weight ratio of the aqueous electrolyte to the DMAPS monomer was 95:5 (Preparation Example 12) or 90:10 (Preparation Example 13), and the MBA crosslinking agent was 0.5 wt% and the KPS was 2 wt% relative to the weight of the DMAPS monomer, and then mixing at 2000 RPM for 10 minutes in a Thinky mixer.

[0162]

[0163] Table 1 below summarizes the compositions of the solutions according to the aqueous electrolyte preparation examples and monomer-electrolyte solution preparation examples 1 to 13.

[0164] Aqueous electrolyte DMAPS monomer AAm monomer MBA crosslinking agent KPS radical initiator Weight-ratio Aqueous electrolyte Preparation Example 100----Monomer-electrolyte solution Preparation Example 1973---Monomer-electrolyte solution Preparation Example 2955---Monomer-electrolyte solution Preparation Example 3937---Monomer-electrolyte solution Preparation Example 4955--2wt% monomer-electrolyte solution relative to DMAPS monomer Preparation Example 59010--2wt% monomer-electrolyte solution relative to DMAPS monomer Preparation Example 68515--2wt% monomer-electrolyte solution relative to DMAPS monomer Preparation Example 7950.254.75 0.5wt% relative to the total weight of monomers Preparation Example 2wt% monomer-electrolyte solution relative to the total weight of monomers 8900.59.5 0.5wt% of the total weight of monomers, 2wt% of the total weight of monomers, preparation example of a monomer-electrolyte solution 9902.57.5 - 2wt% of the total weight of monomers, preparation example of a monomer-electrolyte solution 109055 - 2wt% of the total weight of monomers, preparation example of a monomer-electrolyte solution 11907.52.5 - 2wt% of the total weight of monomers, preparation example of a monomer-electrolyte solution 12955 - 0.5wt% of the DMAPS monomer, 2wt% of the DMAPS monomer, preparation example of a monomer-electrolyte solution 139010 - 0.5wt% of the DMAPS monomer, 2wt% of the DMAPS monomer

[0165] Cathode Preparation Example 1 (LTO + PVDF) Li4Ti5O as the cathode active material 12 (LTO) powder, acetylene black as a conductive material, and PVDF binder were mixed in a weight ratio of 85:7.5:7.5 in a Thinky mixer at 2000 RPM for 10 minutes. This mixture was placed in the organic solvent N-methyl-2-pyrrolidone (NMP) and mixed in a Thinky mixer at 2000 RPM for 10 minutes to obtain a slurry. The obtained slurry was coated onto an aluminum foil current collector and dried at 100 °C to obtain an anode. The active material areal density of the obtained anode was 1.0 mg·cm³. -2 was.

[0166]

[0167] Cathode Preparation Example 2 (LTO + (SBR-CMC))

[0168] Li4Ti5O, a negative electrode active material 12 A slurry was obtained by mixing LTO powder, acetylene black as a conductive material, and a dispersion of a binder consisting of styrene-butadiene rubber and sodium carboxymethylcellulose (SBR-CMC) in a weight ratio of 85:7.5:7.5 in a Thinky mixer at 2000 RPM for 10 minutes. The SBR-CMC dispersion is a binder in the form of an aqueous dispersion containing 3 wt% of SBR and CMC (weight ratio 1:1), wherein the CMC is dissolved and the SBR is dispersed in degassed ultrapure water. The obtained slurry was applied to an aluminum foil current collector and dried at 100 °C to obtain an anode. The active material area density of the obtained anode was 1.0 mg·cm³. -2 was.

[0169]

[0170] Cathode Preparation Example 3 (ZNO + (SBR-CMC))

[0171] Zn2Nb as the negative electrode active material 34 O 87 Using (ZNO), the active material area density of the obtained anode is 2.4 mg·cm³ -2 The anode was obtained using the same method as in Cathode Preparation Example 2, except that...

[0172] Zn2Nb 34 O 87 ZnO is a Wadsley-Roth niobate-based material synthesized by the solid-state method. Specifically, ZnO and Nb2O5 were stoichiometrically mixed via high-energy ball milling, and then calcined at 1200 °C in an atmospheric atmosphere for 4 hours to produce Zn2Nb 34 O 87 I obtained.

[0173]

[0174] Cathode Preparation Example 4 (DMAPS-coated LTO + (SBR-CMC))

[0175] 0.004 g of DMAPS monomer powder was dissolved in 700 µL of dry ethanol. Then, Li4Ti5O, the cathode active material 12 0.2 g of (LTO) powder was dispersed in the obtained solution to obtain a mixture, which was stirred on a hot plate heated to 90 ℃ until the solvent evaporated, and dried in a drying oven at 100 ℃ for 24 hours to obtain DMAPS-coated LTO particles, i.e., powder. Here, DMAPS was contained in an amount of 2 parts by weight per 100 parts by weight of DMAPS-coated LTO particles.

[0176] An anode was obtained using the same method as in Cathode Preparation Example 2, except that instead of LTO powder not coated as a cathode active material, the DMAPS-coated LTO powder obtained above, acetylene black as a conductive material, and a mixture of styrene-butadiene rubber and sodium carboxymethylcellulose (SBR-CMC) as a binder were mixed in a weight ratio of 85:7.5:7.5. The active material area density of the obtained anode was 1.0 mg·cm². -2 was.

[0177]

[0178] Cathode Preparation Example 5 (LTO + (SBR-CMC) + DMAPS)

[0179] A mixture was obtained by adding DMAPS monomer powder to an SBR-CMC aqueous dispersion (containing 3 wt% of SBR and CMC (weight ratio 1:1)) at room temperature and dissolving it while stirring. The concentration of DMAPS in the mixture was 1 wt%. An anode was obtained using the same method as in Cathode Preparation Example 2, except that the SBR-CMC aqueous dispersion containing the dissolved DMAPS monomer obtained above was used instead of the pure SBR-CMC aqueous dispersion. The active material area density of the obtained anode was 1.0 mg·cm². -2 was.

[0180]

[0181] Cathode Preparation Example 6 (LTO + (SBR-CMC) + poly-DMAPS)

[0182] A poly-DMAPS hydrogel was obtained by thermally polymerizing the DMAPS monomer in ultrapure water at a weight ratio of 50:1 to a KPS initiator and gently stirring at 60°C for 24 hours. The obtained poly-DMAPS hydrogel was placed in an SBR aqueous dispersion and dispersed by stirring at room temperature for 30 minutes. Once well dispersed, CMC was added to obtain a binder dispersion in which the final concentration of SBR-CMC (weight ratio 1:1) in the solution was 2 wt% and the final concentration of poly-DMAPS was 3 wt%. At this time, the concentration of SBR-CMC was adjusted to 2 wt% to achieve an appropriate viscosity of the binder dispersion.

[0183] An anode was obtained using the same method as in Cathode Preparation Example 2, except that the poly-DMAPS dispersed SBR-CMC dispersion obtained above was used as the binder instead of the pure SBR-CMC dispersion. The active material area density of the obtained anode was 1.0 mg·cm². -2 was.

[0184]

[0185] Anode Preparation Example 1 (LMO + PVDF)

[0186] LiMn2O4 (LMO) powder as the cathode active material, acetylene black as the conductive material, and PVDF binder were mixed in a weight ratio of 85:7.5:7.5 in a Thinky mixer at 2000 RPM for 10 minutes. This mixture was placed in the organic solvent N-methyl-2-pyrrolidone (NMP) and mixed in a Thinky mixer at 2000 RPM for 10 minutes to obtain a slurry. The obtained slurry was coated onto a titanium current collector and dried at 100 °C to obtain a cathode. The mass distribution of the active material in the obtained cathode was 1.3 mg·cm². -2 was.

[0187]

[0188] Anode Preparation Example 2 (LMO + (SBR-CMC))

[0189] A slurry was obtained by mixing LiMn2O4 (LMO) powder as the cathode active material, acetylene black as the conductive material, and a binder mixture of styrene-butadiene rubber and sodium carboxymethylcellulose (SBR-CMC) in a weight ratio of 85:7.5:7.5 in a Thinky mixer at 2000 RPM for 10 minutes. The SBR-CMC dispersion is a binder in the form of an aqueous dispersion containing 3 wt% of SBR and CMC (weight ratio 1:1), wherein CMC is dissolved and SBR is dispersed in degassed ultrapure water. The obtained slurry was coated onto a titanium current collector and dried at 100 °C to obtain a cathode. The mass distribution of the active material in the obtained cathode was 1.3 mg·cm². -2 was.

[0190]

[0191] Anode Preparation Example 3 (DMAPS-coated LMO + (SBR-CMC))

[0192] 0.004 g of DMAPS monomer powder was dissolved in 700 µL of dry ethanol. Then, 0.2 g of LiMn2O4 (LMO) powder, which is the cathode active material, was dispersed in the obtained solution. The resulting mixture was stirred on a hot plate heated to 90°C until the solvent evaporated, and then dried in a drying oven at 100°C for 24 hours to obtain DMAPS-coated LMO particles, i.e., powder. Here, DMAPS was contained in an amount of 2 parts by weight per 100 parts by weight of DMAPS-coated LMO particles.

[0193] A cathode was obtained using the same method as in Cathode Preparation Example 2, except that instead of the LMO powder not coated as a cathode active material, the DMAPS-coated LMO powder obtained above, acetylene black as a conductive material, and a mixture of styrene-butadiene rubber and sodium carboxymethylcellulose (SBR-CMC) as a binder were mixed in a weight ratio of 85:7.5:7.5. The mass distribution of the active material in the obtained cathode was 1.3 mg·cm². -2 was.

[0194]

[0195] Anode Preparation Example 4 (LMO + (SBR-CMC) + DMAPS)

[0196] A mixed solution was obtained by adding DMAPS monomer powder to an SBR-CMC aqueous dispersion (containing 3 wt% of SBR and CMC (weight ratio 1:1)) at room temperature and dissolving it while stirring. The concentration of DMAPS in the mixed solution was 1 wt%. An anode was obtained using the same method as in Anode Preparation Example 2, except that the SBR-CMC aqueous dispersion containing the dissolved DMAPS monomer obtained above was used instead of the pure SBR-CMC aqueous dispersion. The active material mass distribution of the obtained anode was 1.3 mg·cm². -2 was.

[0197]

[0198] Anode Preparation Example 5 (LMO + (SBR-CMC) + poly-DMAPS)

[0199] A poly-DMAPS hydrogel was obtained by thermally polymerizing the DMAPS monomer in ultrapure water at a weight ratio of 50:1 to a KPS initiator and gently stirring at 60°C for 24 hours. The obtained poly-DMAPS hydrogel was placed in an SBR aqueous dispersion and dispersed by stirring at room temperature for 30 minutes. Once well dispersed, CMC was added to obtain a binder dispersion in which the final concentration of SBR-CMC (weight ratio 1:1) in the solution was 2 wt% and the final concentration of poly-DMAPS was 3 wt%. At this time, the concentration of SBR-CMC was adjusted to 2 wt% to achieve an appropriate viscosity of the binder dispersion.

[0200] A cathode was obtained using the same method as in Cathode Preparation Example 2, except that the poly-DMAPS dispersed SBR-CMC dispersion obtained above was used as the binder instead of the pure SBR-CMC dispersion. The active material mass distribution of the obtained cathode was 1.3 mg·cm². -2 was.

[0201]

[0202] Preparation Example 1 of an aqueous lithium-ion secondary battery

[0203] A modified lower case coated with aluminum on 316L grade stainless steel was prepared, and a plastic gasket was inserted. Then, an anode (LTO+(CMC-SBR)) containing the cathode active material LTO obtained in Cathode Preparation Example 2 and the binder CMC-SBR, a glass microfiber separator, and an anode (LMO+(CMC-SBR)) containing the anode active material LMO obtained in Anode Preparation Example 2 and the binder CMC-SBR obtained were sequentially stacked inside the lower case. Afterward, an aqueous electrolyte obtained in the aqueous electrolyte preparation example was added until the glass fiber separator was completely wetted and overflowed. Subsequently, a 316L grade stainless steel upper case was covered to obtain a coin cell-type battery. To prevent moisture contamination, the storage of materials and the aforementioned battery assembly were carried out in a dry room with a dew point of -36°C and an ambient temperature of 25°C.

[0204]

[0205] Preparation Example 2 of an aqueous lithium-ion secondary battery

[0206] Instead of the anode (LTO+(CMC-SBR)) obtained in Cathode Preparation Example 2, Zn2Nb is used as the cathode active material obtained in Cathode Preparation Example 3. 34 O 87 A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that an anode (ZNO+(CMC-SBR)) containing (ZNO) and a binder CMC-SBR was used.

[0207]

[0208] Examples of preparation of hydrogel electrolyte secondary batteries 1-5

[0209] A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that one of the monomer-electrolyte solutions obtained in Examples 1-5 of the preparation of monomer-electrolyte solutions was used instead of the aqueous electrolyte obtained in Example 1 of the preparation of an aqueous electrolyte.

[0210] The assembled battery was aged at 25°C for 10 hours. Afterwards, a free galvanostatic charge-discharge cycling was performed at least once at 1C with the battery set to a cutoff voltage of 2.8V during charging and 2V during discharging at 25°C to in situ electrochemical polymerization of the monomer in the monomer-electrolyte solution to produce a hydrogel electrolyte secondary battery.

[0211]

[0212] Preparation Example 6 of a Hydrogel Electrolyte Secondary Battery

[0213] A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that the monomer-electrolyte solution obtained in Example 2 of the preparation of a monomer-electrolyte solution was used instead of the aqueous electrolyte obtained in Example 1 of the preparation of an aqueous electrolyte, and the anode (ZNO + (SBR+CMC)) prepared in Example 3 of the preparation of a cathode was used instead of Example 2 of the preparation of a cathode.

[0214] The assembled battery was aged at 25°C for 10 hours. Afterwards, the battery was charged to 2.75V at 25°C at a 1C-rate and left for 5 days (i.e., aged), and then discharged to 1.5V at a 1C-rate (pre-charge / discharge cycle) to electrochemically charge-aging polymerize the monomer in the monomer-electrolyte solution to produce a hydrogel electrolyte secondary battery.

[0215]

[0216] Examples of Preparation of Hydrogel Electrolyte Secondary Battery 7-16

[0217] A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that one of the monomer-electrolyte solutions obtained in Examples 7-13 and 4-6 of the preparation of monomer-electrolyte solutions was used instead of the aqueous electrolyte obtained in Example 1 of the preparation of an aqueous electrolyte.

[0218] The assembled battery was aged at 25°C for 10 hours. Afterwards, the battery was transferred to an oven heated to 80°C and heated for 5 hours, then cooled to room temperature to thermally polymerize the monomer in the monomer-electrolyte solution to produce a hydrogel electrolyte secondary battery.

[0219] Specifically, as summarized in Table 2 below, the secondary batteries according to hydrogel electrolyte secondary battery preparation examples 7-13 each used monomer-electrolyte solutions according to monomer-electrolyte solution preparation examples 7-13, and the secondary batteries according to hydrogel electrolyte secondary battery preparation examples 14-16 each used monomer-electrolyte solutions according to monomer-electrolyte solution preparation examples 4-6.

[0220]

[0221] Preparation Example 17 of a Hydrogel Electrolyte Secondary Battery

[0222] A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that the monomer-electrolyte solution obtained in Example 2 of the preparation of a monomer-electrolyte solution was used instead of the aqueous electrolyte obtained in Example 1 of the preparation of an aqueous electrolyte, the anode (ZNO + (SBR+CMC)) prepared in Example 3 of the preparation of a cathode was used instead of Example 2 of the preparation of a cathode, and three glass microfiber separators (Q1, Q2, Q3) were used between the anode and the cathode.

[0223] The assembled battery was aged at 25°C for 10 hours. Afterwards, the battery was charged to 2.75V at 25°C at a 1C-rate and left for 5 days (i.e., aged), and then discharged to 1.5V at a 1C-rate (pre-charge / discharge cycle) to electrochemically charge-aging polymerize the monomer in the monomer-electrolyte solution to produce a hydrogel electrolyte secondary battery.

[0224]

[0225] Example of manufacturing a secondary battery having DMAPS-coated active material

[0226] A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that a cathode (LTO+(CMC-SBR)) containing DMAPS-coated LTO and binder CMC-SBR obtained in Example 4 of the preparation of a cathode was used instead of the cathode (LTO+(CMC-SBR)) obtained in Example 2 of the preparation of a cathode, and a cathode (DMAPS-coated LMO + (SBR-CMC)) containing DMAPS-coated LMO and CMC-SBR obtained in Example 3 of the preparation of a cathode was used instead of the cathode (LTO+(CMC-SBR)) obtained in Example 2 of the preparation of a cathode.

[0227] The assembled battery was aged at 25°C for 10 hours. Afterwards, the battery was subjected to at least one galvanostatic charge-discharge cycling at 1C with the cutoff voltage set to 2.8V during charging and 2V during discharging at 25°C to in situ electrochemically polymerize the DMAPS monomer coated with the negative electrode active material particles and the positive electrode active material particles.

[0228]

[0229] Preparation Example 1 of a secondary battery having electrodes including DMAPS

[0230] A battery was assembled in the same manner as in Example 1 of the preparation of an aqueous lithium-ion secondary battery, except that the cathode (LTO+(SBR-CMC)+DMAPS) containing LTO, binder CMC-SBR, and DMAPS monomer obtained in Example 5 of the preparation of a cathode was used instead of the cathode obtained in Example 2 of the preparation of a cathode, and the anode (LMO+(SBR-CMC)+DMAPS) containing LMO, binder CMC-SBR, and DMAPS monomer obtained in Example 4 of the preparation of anode (LMO+(SBR-CMC)+DMAPS) obtained in Example 4 of the preparation of anode (LMO) was used instead of the anode obtained in Example 2 of the preparation of anode (LMO).

[0231] The assembled battery was aged at 25°C for 10 hours. Afterwards, the battery was subjected to at least one galvanostatic charge-discharge cycling at 1C with the cutoff voltage set to 2.8V during charging and 2V during discharging at 25°C to in situ electrochemical polymerize the DMAPS monomers added to the anode and cathode.

[0232]

[0233] Preparation Example 2 of a secondary battery having electrodes including DMAPS

[0234] A battery was assembled in the same manner as in Example 1 of a water-based lithium-ion secondary battery, except that instead of the cathode obtained in Example 2 of a cathode preparation, a cathode (LTO+(SBR-CMC)+poly-DMAPS) comprising LTO, binder CMC-SBR, and poly-DMAPS by thermal polymerization obtained in Example 6 of a cathode preparation was used, and instead of the anode obtained in Example 2 of an anode preparation, an anode (LMO+(SBR-CMC)+poly-DMAPS) comprising LMO, binder CMC-SBR, and poly-DMAPS by thermal polymerization obtained in Example 5 of an anode preparation was used.

[0235]

[0236] Table 2 below summarizes the electrolyte solution, anode, cathode, monomer polymerization method used in water-based lithium-ion secondary battery preparation examples 1-2, hydrogel electrolyte secondary battery preparation examples 1-17, secondary battery preparation examples having DMAPS-coated active material, and secondary battery preparation examples 1-2 having electrodes containing DMAPS, as well as the capacity retention rate after 100 cycles of the battery obtained in each preparation example.

[0237] Electrolyte Solution Anode Anode Monomer Polymerization Method Capacity Retention Rate After 100 Cycles Aqueous Lithium-ion Secondary Battery Preparation Example 1 Aqueous Electrolyte Preparation Example Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) -22.5% Aqueous Lithium-ion Secondary Battery Preparation Example 2 Aqueous Electrolyte Preparation Example Preparation Example 3 (ZNO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) -80.8% Hydrogel Electrolyte Secondary Battery Preparation Example 1 Monomer-Electrolyte Solution Preparation Example 1 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) In-situ Electrochemical Polymerization 59.1% Hydrogel Electrolyte Secondary Battery Preparation Example 2 Monomer-Electrolyte Solution Preparation Example 2 Preparation Example Preparation Example 2 (LTO+(SBR-CMC)) 46.1% Hydrogel Electrolyte Secondary Battery Preparation Example 3 Monomer-Electrolyte Solution Preparation Example 3 Preparation Example 2 (LTO+(SBR-CMC)) 22.7% Hydrogel Electrolyte Secondary Battery Preparation Example 4 Monomer-Electrolyte Solution Preparation Example 4 Preparation Example 2 (LTO+(SBR-CMC)) 43.0% Hydrogel Electrolyte Secondary Battery Preparation Example 5 Monomer-Electrolyte Solution Preparation Example 5 Preparation Example 2 (LTO+(SBR-CMC)) 10.0% Hydrogel Electrolyte Secondary Battery Preparation Example 6 Monomer-Electrolyte Solution Preparation Example 2 Preparation Example 3 (ZNO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) Electrochemical charge-aging polymerization 90.1% hydrogel electrolyte secondary battery Preparation Example 7 Monomer-electrolyte solution Preparation Example 7 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) Thermal polymerization 0.2% hydrogel electrolyte secondary battery Preparation Example 8 Monomer-electrolyte solution Preparation Example 8 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) 0.3% hydrogel electrolyte secondary battery Preparation Example 9 Monomer-electrolyte solution Preparation Example 9 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2(LMO+(SBR-CMC))10%(Initial capacity: 10 mAh g -1) Hydrogel electrolyte secondary battery Preparation Example 10 Monomer-electrolyte solution Preparation Example 10 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) 15% (Initial capacity: 23 mAh g -1Hydrogel electrolyte secondary battery Preparation Example 11 Monomer-electrolyte solution Preparation Example 11 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) 14% Hydrogel electrolyte secondary battery Preparation Example 12 Monomer-electrolyte solution Preparation Example 12 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) 23.5% Hydrogel electrolyte secondary battery Preparation Example 13 Monomer-electrolyte solution Preparation Example 13 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example 2 (LMO+(SBR-CMC)) 35% Hydrogel electrolyte secondary battery Preparation Example 14 Monomer-electrolyte solution Preparation Example 4 Preparation Example 2 (LTO+(SBR-CMC)) Preparation Example Preparation Example 15 of a secondary battery with a monomer-electrolyte solution, 2 (LMO + (SBR-CMC)) 11% hydrogel electrolyte, Preparation Example 5, Preparation Example 2 (LTO + (SBR-CMC)) 40% hydrogel electrolyte, Preparation Example 16 of a secondary battery with a monomer-electrolyte solution, Preparation Example 6, Preparation Example 2 (LTO + (SBR-CMC)) 48% hydrogel electrolyte, Preparation Example 17 of a secondary battery with a monomer-electrolyte solution, Preparation Example 2, Preparation Example 3 (ZNO + (SBR-CMC)) 48% hydrogel electrolyte, Preparation Example 2 (LMO + (SBR-CMC)) electrochemical charge-aging polymerization, Preparation Example 4 of a secondary battery having an 88% DMAPS-coated active material, Preparation Example of a water-based electrolyte, Preparation Example 4 (DMAPS-coated LTO+(SBR-CMC)) Preparation Example 3 (DMAPS-coated LMO+(SBR-CMC)) In-situ electrochemical polymerization Secondary battery having electrodes containing 40.3% DMAPS Preparation Example 1 Aqueous electrolyte Preparation Example 5 (LTO+(SBR-CMC)+DMAPS) Preparation Example 4 (LMO+(SBR-CMC)+DMAPS) In-situ electrochemical polymerization Secondary battery having electrodes containing 44.8% DMAPS Preparation Example 2 Aqueous electrolyte Preparation Example 6 (LTO+(SBR-CMC)+poly-DMAPS) Preparation Example 5 (LMO+(SBR-CMC)+poly-DMAPS) Thermal polymerization 57.1%

[0238] Figure 3a shows the Raman spectra of the DMAPS monomer powder and its polymer, and Figure 3b shows the FTIR spectra of the DMAPS monomer powder, its polymer, and the aqueous electrolyte obtained in the aqueous electrolyte preparation example. Referring to Figure 3a, 1635 cm⁻¹ -1 The gray-highlighted peak is associated with the carbon-carbon double bond (C=C) of the DMAPS monomer, and at 1635 cm⁻¹ in the DMAPS polymer. -1 It can be seen that the peak of has disappeared.

[0239] Referring to Fig. 3b, the water of the electrolyte (1600-1670 cm -1 The related peak is C=C(1635-1640 cm⁻¹) -1 Since it blocks ), in order to evaluate polymerization, the conjugate C=O (1715-1730 cm²) of the α,β-unsaturated ester (C=CC=O) group of DMAPS -1 The relevant peaks must be used. When DMAPS polymerizes, the C=O peak shifts to a higher wavenumber because it is no longer conjugated with C=C, and the non-conjugated C=O is at 1730–1740 cm⁻¹. -1 It is located at . The monomer DMAPS exhibits conjugated C=O at 1715–1730 cm⁻¹. -1 While a peak of strong intensity is observed in this region, the electrolyte containing polymerized DMAPS does not show a peak in this region. Additionally, polymerized DMAPS shows a broad peak of lower intensity associated with C=O that has shifted to a non-conjugated state.

[0240]

[0241] FIG. 4a is an FTIR spectrum for a glass fiber separator containing DMAPS monomer powder, a bare glass microfiber separator used in Example 1 of preparation of an aqueous lithium-ion secondary battery, and a hydrogel electrolyte formed by in situ electrochemical polymerization of DMAPS monomer obtained by decomposing the battery obtained from Example 1 of preparation of a hydrogel electrolyte secondary battery, and FIG. 4b is the 1500–1850 cm⁻¹ of FIG. 4a. -1 This is the FTIR spectrum with the region magnified. Here, 40 free constant current charge-discharge cycles were performed for in-situ electrochemical polymerization.

[0242] Referring to Fig. 4a, 1715–1730 cm -1 A peak associated with the α,β-unsaturated ester functional group (-C(O)-C=C-) characterizing the DMAPS monomer appeared, while no peak appeared in this region in the bare glass microfiber membrane.

[0243] Meanwhile, in a glass fiber separator containing a hydrogel electrolyte electrochemically polymerized in situ with DMAPS monomers (ECP DMAPS contained fiberglass) at 1500–1000 cm -1 Various peaks associated with DMAPS appeared, which means that DMAPS contains a separator.

[0244] Referring to Fig. 4b, in the DMAPS monomer, the 1715–1725 cm⁻¹ related to the conjugated C=O of the α,β-unsaturated ester (C=CC=O) group -1 While a peak appeared, in glass fiber separators containing hydrogel electrolytes in situ electropolymerized DMAPS monomers, the peak was 1730–1740 cm⁻¹. -1 A non-conjugated C=O peak was observed in the region, which indicates that the DMAPS monomer was polymerized in a glass fiber separator containing a hydrogel electrolyte in which the DMAPS monomer was in situ electrochemically polymerized.

[0245]

[0246] FIG. 5a is a schematic diagram showing glass fiber separators (Q1, Q2, Q3) containing an anode (ZNO), a cathode (LMO), and a hydrogel electrolyte electrochemically charged and aged polymerized from three DMAPS monomers between them, obtained by decomposing the cell of the hydrogel electrolyte secondary battery prepared in Example 17 of preparation of hydrogel electrolyte before or after main charge and discharge, and FIG. 5b is an FTIR spectrum showing an anode (ZNO), a cathode (LMO), and three glass fiber separators (Q1, Q2, Q3) between them, obtained by decomposing the cell assembled in Example 17 of preparation of hydrogel electrolyte secondary battery after a pre-charge and discharge cycle before the main charge and discharge cycle (0 C), after 10 main charge and discharge cycles at 1 C (10 C), and after 300 main charge and discharge cycles (300 C).

[0247] Referring to Fig. 5a, among the glass fiber separators (Q1, Q2, Q3) containing a hydrogel electrolyte in which DMAPS monomers are electrochemically charge-aged polymerized, Q1 is positioned adjacent to the anode (ZNO), Q3 is positioned adjacent to the anode (LMO), and Q2 is positioned between Q1 and Q3.

[0248] Referring to Fig. 5b, it can be seen that polymerization proceeded during the pre-charge / discharge cycle from the fact that the conjugated C=O peak shifted to the non-conjugated C=O peak only in the anode (LMO) and Q3 facing the anode (LMO) before the main charge / discharge cycle (0 C). After 10 cycles (10 C), it can be seen that DMAPS in Q1 was also polymerized, and since the C=O peak shifted slightly in the non-conjugated direction or non-polymerizable conjugated C=O was also observed in the anode (ZNO), it may mean that DMAPS was partially polymerized in the anode (ZNO) or that unpolymerized DMAPS was captured within the SEI. Q2, which is furthest from the surface of the electrodes such as the cathode or anode, did not show any shift in the C=O peak before the charge / discharge cycle (0 C) and after 10 cycles (10 C), but showed a shift in the C=O peak after 300 cycles (300 C), indicating that the contained DMAPS was polymerized.

[0249] From this, gradient polymerization can be observed in which the monomer in the monomer-electrolyte solution polymerizes first on the electrode surface, and due to the high viscosity of the monomer-electrolyte solution, the entire polymerization was not completely completed even after 10 cycles, and it can be seen that a number of cycles, about 40 cycles, are required for the complete polymerization of the monomer-electrolyte solution.

[0250]

[0251] FIG. 6a is a schematic diagram showing glass fiber separators (Q1, Q2, Q3) containing an anode (ZNO), a cathode (LMO), and a hydrogel electrolyte electrochemically charge-aged polymerized from three DMAPS monomers between them, obtained by decomposing the cell of the hydrogel electrolyte secondary battery prepared in Example 17 of Preparation of Hydrogel Electrolyte Secondary Battery before or after main charge-discharge; FIG. 6b is a Raman spectrum for three glass fiber separators (Q1, Q2, Q3) obtained by decomposing the cell prepared in Example 17 of Preparation of Hydrogel Electrolyte Secondary Battery before a main charge-discharge cycle (0 C); and FIG. 6c is a diagram showing three glass fiber separators (Q1, Q2, Q3) obtained by decomposing the cell prepared in Example 17 of Preparation of Hydrogel Electrolyte Secondary Battery after 10 main charge-discharge cycles at 1 C (10 C) and after 300 main charge-discharge cycles (300 C). This is the Raman spectrum for Q2, Q3.

[0252] Referring to Figures 6a and 6b, when observing that the C=C peak disappears or its intensity decreases only in Q3 before the main charge / discharge cycle (0 C), it can be seen that polymerization of DMAPS proceeded only in Q3 facing the anode (LMO) during the pre-charge / discharge cycle.

[0253] Referring to Figures 6a and 6c, when observing that the C=C peak of Q1 disappears or its intensity decreases after 10 cycles of main charging and discharging (10 C), it can be seen that DMAPS in Q1 was polymerized during the 10 cycles of main charging and discharging. Meanwhile, when observing that the C=C peak of Q2, which is furthest from the surface of electrodes such as the cathode or anode, disappears or its intensity decreases after 300 cycles of main charging and discharging (300 C), it can be seen that DMAPS in Q2 was polymerized during the 300 cycles of main charging and discharging.

[0254] From this, as observed in Fig. 5b, it can be seen that the monomer in the monomer-electrolyte solution undergoes gradient polymerization, where it polymerizes first on the electrode surface, and due to the high viscosity of the monomer-electrolyte solution, it was not completely polymerized even after 10 main charge-discharge cycles, and it can be seen that a long number of cycles are required for the complete polymerization of the monomer-electrolyte solution.

[0255]

[0256] FIGS. 7a and 7b show the battery (LTO / LMO) according to Example 1 of preparation of an aqueous lithium-ion secondary battery using a pure aqueous electrolyte without the addition of amphoteric ionic monomers such as DMAPS, with 1C (theoretical capacity 148 mAh g -1 The voltage profile after the first two constant current charge / discharge cycles and the graph showing the change in capacity after a total of 100 cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0257] Referring to Fig. 7a, the difference in charge capacity between the first and second cycles was estimated to be due to the active formation of the solid electrolyte interface (SEI) caused by the decomposition of free water during the first charge cycle. Free water is formed by the insertion of lithium ions into the anode.

[0258] Referring to Fig. 7b, the capacity retention rate of the battery after 100 cycles was 22.5%. This rapid capacity degradation of the battery is due to the active formation of HF acid during charge-discharge cycles, and the generated HF can attack the cathode material by dissolving manganese (Mn) from the LiMn2O4 structure. This dissolution of Mn can lead to structural instability and loss of active material, thereby degrading capacity and overall battery performance. Additionally, dissolved manganese ions migrate to the anode and form a solid electrolyte interface (SEI) that hinders the movement of lithium ions, which can cause further performance degradation.

[0259]

[0260] FIGS. 8a and 8b show the battery (ZNO / LMO) according to Preparation Example 2 of an aqueous lithium-ion secondary battery using a pure aqueous electrolyte without the addition of amphoteric ionic monomers such as DMAPS, with 1C (theoretical capacity 148 mAh g -1 The voltage profile after the first two constant current charge / discharge cycles and the graph showing the change in capacity after a total of 300 cycles are shown, respectively (voltage range is 1.5V ~ 2.75V).

[0261] Referring to Fig. 8a, the difference in charge capacity between the first and second cycles was estimated to be due to the active formation of the solid electrolyte interface (SEI) caused by the decomposition of free water during the first charge cycle. Free water is formed by the insertion of lithium ions into the anode.

[0262] Referring to Fig. 8b, the capacity retention rate of the battery after 100 cycles is 80.8%, and the capacity retention rate after 300 cycles is 61.5%.

[0263] Referring simultaneously to FIGS. 7a, FIGS. 7b, FIGS. 8a, and FIGS. 8b, the battery (ZNO / LMO) according to Example 2 of the aqueous lithium-ion secondary battery preparation had a slightly lower average battery voltage compared to the battery (LTO / LMO) according to Example 1 of the aqueous lithium-ion secondary battery preparation, but provided better long-term performance. However, the battery (ZNO / LMO) according to Example 2 of the aqueous lithium-ion secondary battery preparation also did not have a significantly superior capacity retention rate, which means that it still has the same problem of HF-induced damage as the battery (LTO / LMO) according to Example 1 of the aqueous lithium-ion secondary battery preparation.

[0264]

[0265] FIGS. 9a and 9b show the battery (LTO / LMO) according to Example 1 of Preparation of a hydrogel electrolyte secondary battery using an aqueous electrolyte containing the amphoteric ionic monomer DMAPS, at 1C (theoretical capacity 148 mAh g) during preparation. -1The voltage profile after performing the initial 2 free constant current charge / discharge cycles and the graph showing the change in capacity when performing a total of 100 constant current charge / discharge cycles at 1C including 2 free constant current charge / discharge cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0266] FIGS. 10a and 10b show the hydrogel electrolyte secondary battery (LTO / LMO) according to Preparation Example 2 using an aqueous electrolyte containing the amphoteric ionic monomer DMAPS during preparation at 1C (theoretical capacity 148 mAh g⁻¹). -1 The voltage profile after performing the initial 2 free constant current charge / discharge cycles and the graph showing the change in capacity when performing a total of 100 constant current charge / discharge cycles at 1C including 2 free constant current charge / discharge cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0267] FIGS. 11a and 11b show the hydrogel electrolyte secondary battery (LTO / LMO) according to Preparation Example 3 using an aqueous electrolyte containing the amphoteric ionic monomer DMAPS during preparation at 1C (theoretical capacity 148 mAh g⁻¹). -1 The voltage profile after performing the initial 2 free constant current charge / discharge cycles and the graph showing the change in capacity when performing a total of 100 constant current charge / discharge cycles at 1C including 2 free constant current charge / discharge cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0268] Referring to FIGS. 9a, 10a, and 11a, the difference in charge capacity between the first and second cycles was presumed to be due to the active formation of the solid electrolyte interface (SEI) caused by the decomposition of free water during the first charge cycle. However, compared to the batteries according to aqueous lithium-ion secondary battery preparation examples 1 and 2 in FIGS. 7a and 8a, the difference in charge capacity between the first and second cycles is less pronounced because a smaller amount of free water was decomposed, indicating that the stability of the electrolyte was improved by including the DMAPS polymer. This was presumed to be because DMAPS has amphoteric ionic functional groups.

[0269] Referring to FIG. 9b, the capacity retention rate after 100 cycles of the battery according to Example 1 of the hydrogel electrolyte secondary battery is 59.1%, referring to FIG. 10b, the capacity retention rate after 100 cycles of the battery according to Example 2 of the hydrogel electrolyte secondary battery is 46.1%, and referring to FIG. 11b, the capacity retention rate after 100 cycles of the battery according to Example 3 of the hydrogel electrolyte secondary battery is 22.7%.

[0270] Referring simultaneously to FIGS. 9b, FIGS. 10b, and FIGS. 11b, the battery according to Example 1 of hydrogel electrolyte secondary battery preparation exhibits the best performance despite containing the smallest amount of DMAPS (3 wt%) in the electrolyte, which demonstrates that unwanted secondary parasitic reactions may be induced during the electrochemical polymerization process as the DMAPS monomer concentration increases. Meanwhile, considering that the capacity retention rate after 100 cycles of the battery (LTO / LMO) according to Example 1 of aqueous lithium-ion secondary battery preparation in FIG. 7b is 22.5%, it was found that the capacity retention rates after 100 cycles of the batteries according to Examples 1 to 3 of hydrogel electrolyte secondary battery preparation were improved. This was presumed to be due to the fact that DMAPS has an amphoteric ionic functional group.

[0271]

[0272] FIGS. 12a and 12b show 1C (theoretical capacity 148 mAh g) for the battery (ZNO / LMO) according to Hydrogel Electrolyte Secondary Battery Preparation Example 6. -1 The voltage profile after the first two constant current charge / discharge cycles and the graph showing the change in capacity after a total of 300 cycles are shown, respectively (voltage range is 1.5V ~ 2.75V).

[0273] Referring to Fig. 12a, the dotted line indicates that the battery assembled during the process of preparing Example 6 of a hydrogel electrolyte secondary battery is aged for 10 hours, then first charged to 2.75V at 25°C at a 1C-rate, stopped for 5 days after charging, and discharged when the in-situ polymerization process is finished (pre-charge / discharge cycle). The straight line indicates the first main charge / discharge cycle after the polymerization process, and the dotted line indicates the second main charge / discharge cycle.

[0274] Referring to Fig. 12b, the capacity retention rate after 100 cycles of the battery according to Example 6 of the hydrogel electrolyte secondary battery is 90.1%, and the capacity retention rate after 300 cycles is 82%. Meanwhile, considering that the capacity retention rate after 100 cycles of the battery (ZNO / LMO) according to Example 2 of the aqueous lithium-ion secondary battery in Fig. 8b is 80.8%, it was found that the capacity retention rates after 100 cycles of the batteries according to Example 6 of the hydrogel electrolyte secondary battery were improved. This was presumed to be because DMAPS has amphoteric ionic functional groups.

[0275]

[0276] FIG. 13 shows 1C (theoretical capacity 148 mAh g) for the batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 7 and 8. -1 This graph shows the change in capacity when a total of 100 constant current charge / discharge cycles are performed (voltage range is 2V ~ 2.8V).

[0277] Referring to FIG. 13, the battery in which the total weight of the DMAPS monomer and AAm monomer according to Example 7 of the hydrogel electrolyte secondary battery preparation is 5 wt%, and the battery in which the total weight of the DMAPS monomer and AAm monomer according to Example 8 of the hydrogel electrolyte secondary battery preparation is 10 wt%, both show a rapid decrease in capacity after 20 and 30 cycles, respectively. This was presumed to be due to the decomposition of the polymer structure caused by the continuous attack of hydrofluoric acid (HF) generated by the relatively high temperature applied during the thermal polymerization process and hydrofluoric acid generated during the charge-discharge process.

[0278]

[0279] FIG. 14 shows 1C (theoretical capacity 148 mAh g) for batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 9 to 11. -1 This graph shows the change in capacity when a total of 100 constant current charge / discharge cycles are performed (voltage range is 2V ~ 2.8V).

[0280] Referring to FIG. 14, compared to hydrogel electrolyte secondary battery preparation example 8, hydrogel electrolyte secondary battery preparation examples 9 to 11, in which the content of DMAPS monomer was increased while the content of AAm monomer was decreased without using an MBA crosslinking agent, show that performance deteriorates as the concentration of AAm increases. This is presumed to be because acrylamide is unstable in the absence of a crosslinking agent and decomposes immediately, blocking the electrode surface.

[0281]

[0282] FIG. 15 shows 1C (theoretical capacity 148 mAh g) for batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 12 to 13. -1 This graph shows the change in capacity when a total of 100 constant current charge / discharge cycles are performed (voltage range is 2V ~ 2.8V).

[0283] Referring to Fig. 15, the performance of a hydrogel electrolyte thermally polymerized using a crosslinking agent with a monomer composed solely of DMAPS without AAm is superior to that of a mixed monomer of DMAPS and AAm. When containing 10 wt% DMAPS, 105 mAh g⁻¹ -1 It showed a higher capacity and a retention rate of 35% after 100 cycles, and showed lower performance when containing 5 wt% DMAPS.

[0284] As indicated by the fact that the hydrogel electrolyte cell according to Example 2, which contains 5 wt% of DMAPS and polymerizes DMAPS by in-situ electrochemical polymerization, showed a retention rate of 46.1% after 100 cycles (Fig. 10), it can be seen that obtaining a hydrogel electrolyte by in-situ electrochemical polymerization rather than thermal polymerization demonstrates superior battery durability.

[0285]

[0286] FIG. 16 shows 1C (theoretical capacity 148 mAh g) for batteries (LTO / LMO) according to hydrogel electrolyte secondary battery preparation examples 14 to 16. -1 This graph shows the change in capacity when a total of 100 constant current charge / discharge cycles are performed (voltage range is 2V ~ 2.8V).

[0287] Referring to Fig. 16, the performance of the DMAPS hydrogel electrolyte thermally polymerized without a crosslinking agent is superior to that of the case where a crosslinking agent is used. The best performance was observed when using 15 wt% DMAPS, with a value of 93 mAh g⁻¹. -1It showed a capacity of 48% after 100 cycles. Meanwhile, as shown in FIG. 10b, the battery according to Example 2 of a hydrogel electrolyte secondary battery, which contains 5 wt% of DMAPS in the electrolyte and is formed by in situ electrochemical polymerization, showed a capacity retention rate of 46.1% after 100 cycles; whereas the battery according to Example 12 of a hydrogel electrolyte secondary battery, which contains 5 wt% of DMAPS and KPS radical initiator in the electrolyte and is formed by thermal polymerization, showed a capacity retention rate of 23.5% after 100 cycles, so it can be seen that the electrochemically polymerized hydrogel electrolyte exhibits better stability.

[0288]

[0289] FIG. 17a is the FTIR spectrum for an anode in which the DMAPS monomer was in situ electrochemically polymerized, obtained by disassembling the battery obtained in the secondary battery preparation example having DMAPS monomer powder, the anode (LTO electrode) obtained in Cathode Preparation Example 2, and the DMAPS-coated active material, after one cycle of pre-charge / discharge or ten cycles of main charge / discharge, and FIG. 17b is the 1500–1850 cm⁻¹ of FIG. 17a. -1 This is an FTIR spectrum with the region magnified.

[0290] Referring to Fig. 17a, the DMAPS monomer is 1500 to 1000 cm⁻¹ -1 Along with various DMAPS-related peaks in the region, 1715–1725 cm⁻¹ -1 The emphasized peak of the region is shown. 1715 ~ 1725 cm -1 The peak in the region is associated with the conjugate C=O of the α,β-unsaturated ester functional group (-C(O)-C=C-).

[0291] However, the anode obtained after in situ electrochemical polymerization of a cell containing an anode with DMAPS-coated LTO is 1500 to 1000 cm⁻¹ -1Various peaks associated with DMAPS appeared in the region, indicating that DMAPS is covering the electrode. Meanwhile, the anode obtained after in-situ electrochemical polymerization of a cell containing an anode with DMAPS-coated LTO exhibited peaks at 1715–1725 cm⁻¹. -1 The peak in the region was not shown.

[0292] Referring to Fig. 17b, in the anode obtained by decomposing a cell containing an anode having DMAPS-coated LTO after in-situ electrochemical polymerization by charging and discharging one or ten cycles, the value is 1715–1725 cm⁻¹. -1 The peak in the region shows a shift toward the non-conjugated C=O side, indicating DMAPS polymerization. In particular, the decomposed sample after 10 charge-discharge cycles shows a more distinct shift, indicating that the in situ polymerization process is slow and requires several cycles to complete.

[0293]

[0294] FIGS. 18a and 18b show the 1C (theoretical capacity 148 mAh g) for a battery (DMAPS-coated LTO / DMAPS-coated LMO) according to an example of secondary battery preparation having a DMAPS-coated active material. -1 The voltage profile after performing the initial 2 free constant current charge / discharge cycles and the graph showing the change in capacity after performing a total of 100 constant current charge / discharge cycles including the free constant current charge / discharge cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0295] Referring to Fig. 18a, the difference in charge capacity between the first and second pre-charge / discharge cycles is due to the active formation of the solid electrolyte interface (SEI) during the first charge cycle, caused by unwanted secondary parasitic reactions resulting from the decomposition of free water or electrochemical polymerization reactions.

[0296] Referring to Fig. 18b, the capacity retention rate after 100 cycles is 40.3%. The relatively low initial capacity may be due to unwanted secondary parasitic reactions occurring during the electrochemical polymerization reaction. However, compared to the capacity retention rate of 22.5% after 100 cycles of the battery according to Example 1 of the aqueous lithium-ion secondary battery using active material particles not coated by DMAPS as shown in Fig. 7b, it can be confirmed that there was a significant improvement in the capacity retention rate as the active material was coated with DMAPS.

[0297]

[0298] FIG. 19a is the FTIR spectrum for the DMAPS monomer powder, the anode (LTO electrode) obtained in Cathode Preparation Example 2, and the anode (poly DMAPS + LTO) obtained in Cathode Preparation Example 6, and FIG. 19b is the 1500–1850 cm⁻¹ of FIG. 19a. -1 This is an FTIR spectrum with the region magnified.

[0299] Referring to Fig. 19a, the DMAPS monomer is 1500 to 1000 cm⁻¹ -1 Along with various DMAPS-related peaks in the region, 1715–1725 cm⁻¹ -1 The emphasized peak of the region is shown. 1715 ~ 1725 cm -1 The peak in the region is associated with the conjugate C=O of the α,β-unsaturated ester functional group (-C(O)-C=C-).

[0300] However, the anode containing poly DMAPS is 1500 to 1000 cm -1 Various peaks associated with DMAPS appeared in the region, indicating that DMAPS covers the entire electrode. Meanwhile, the anode containing poly DMAPS is at 1715–1725 cm⁻¹. -1 The peak in the region was not shown.

[0301] Referring to Fig. 19b, at the anode containing poly DMAPS, 1715–1725 cm-1 The peak of the region is at 1730–1740 cm -1 It shows that the region has moved toward the non-conjugated C=O side, which indicates DMAPS polymerization.

[0302]

[0303] FIGS. 20a and 20b show the 1C (theoretical capacity 148 mAh g) for a secondary battery according to Example 1 of Preparation (LTO+DMAPS / LMO+DMAPS) having electrodes including DMAPS. -1 The voltage profile after performing the initial 2 free constant current charge / discharge cycles and the graph showing the change in capacity after performing a total of 100 constant current charge / discharge cycles including the free constant current charge / discharge cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0304] Referring to Fig. 20a, the difference in charge capacity between the first and second pre-charge / discharge cycles is due to the active formation of the solid electrolyte interface (SEI) during the first charge cycle, caused by unwanted secondary parasitic reactions resulting from the decomposition of free water or electrochemical polymerization reactions.

[0305] Referring to Fig. 20b, the capacity retention rate after 100 cycles is 44.8%. The relatively low initial capacity may be due to unwanted secondary parasitic reactions occurring during the electrochemical polymerization reaction. However, compared to the capacity retention rate of 22.5% after 100 cycles of the battery according to Example 1 of the aqueous lithium-ion secondary battery using electrodes not containing DMAPS as shown in Fig. 7b, it can be confirmed that there was a significant improvement in the capacity retention rate with the use of electrodes containing DMAPS.

[0306]

[0307] FIGS. 21a and 21b show the 1C (theoretical capacity 148 mAh g) for a secondary battery according to Preparation Example 2 (LTO+poly-DMAPS / LMO+poly-DMAPS) having electrodes including DMAPS. -1 The voltage profile after the first two constant current charge / discharge cycles and the graph showing the change in capacity after a total of 100 constant current charge / discharge cycles are shown, respectively (voltage range is 2V ~ 2.8V).

[0308] Referring to Fig. 21a, the difference in charge capacity between the first and second pre-charge / discharge cycles is due to the active formation of the solid electrolyte interface (SEI) caused by unwanted secondary parasitic reactions resulting from the decomposition of free water during the first charge cycle. However, the thermally polymerized DMAPS polymer significantly reduced the amount of decomposed free water, exhibiting superior performance compared to a cell without amphoteric ionic polymers (Figs. 7a and 7b).

[0309] Referring to Fig. 21b, the capacity retention rate after 100 cycles is 57.1%. The relatively low initial capacity may be due to unwanted secondary parasitic reactions occurring during the electrochemical polymerization reaction. However, compared to the capacity retention rate of 22.5% after 100 cycles of the battery according to Example 1 of the aqueous lithium-ion secondary battery using electrodes not containing DMAPS as shown in Fig. 7b, it can be confirmed that there was a significant improvement in the capacity retention rate with the use of electrodes containing DMAPS.

[0310]

[0311] Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications and changes are possible by those skilled in the art within the technical spirit and scope of the present invention.

Claims

1. Anode active material layer; cathode active material layer; and A aqueous electrolyte located between the positive electrode active material layer and the negative electrode active material layer, comprising a lithium salt and an aqueous solvent, wherein the mass of the lithium salt is greater than the mass of the aqueous solvent, A water-based lithium-ion battery in which at least one of the positive active material layer and the negative active material layer comprises an ionic polymer.

2. In Paragraph 1, A water-based lithium-ion battery in which the above-mentioned ionic polymers are non-crosslinked linear polymers.

3. In Paragraph 1, A water-based lithium-ion battery in which all monomers included in the above-mentioned amphoteric polymer are monomers containing amphoteric functional groups.

4. In Paragraph 1, A water-based lithium-ion battery in which the above-mentioned ionic polymers are homopolymers formed by polymerizing identical monomers.

5. In Paragraph 1, A water-based lithium-ion battery in which the above-mentioned amphoteric polymer is polymerized from a monomer represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R1 is hydrogen or a methyl group, Z is O or NH, m is 0 or 1, L1 and L2 are directly bonded or C1-C4 alkylene groups regardless of each other, and either X or Y is a moiety containing the cationic functional group and the other is a moiety containing the anionic functional group.

6. In Paragraph 5, A water-based lithium-ion battery in which X is a cationic functional group that is ammonium, pyridinium, or pyrazolium, and Y is an anionic functional group that is a sulfonate or carboxylate.

7. In Paragraph 1, The above-mentioned amphoteric polymer is N-substituted acrylamide sulfobetaine, 1-(3-sulfopropyl)-2-vinylpyridinium hydroxide inner salt, 3-sulfopropyldimethyl-3-methacrylamidopropylammonium inner salt, 1-(4-vinylpyridin-1-ium-1-yl)propane-1-sulfonate, 2-methacryloyloxyethyl phosphorylcholine, An aqueous lithium-ion battery polymerized from monomers comprising 3-(1-vinyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonate, carboxybetaine acrylamide, N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine, or a combination of two or more of these.

8. In Paragraph 7, A water-based lithium-ion battery in which the above-mentioned amphoteric polymer is polymerized from N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine.

9. In Paragraph 1, A water-based lithium-ion battery having a molal concentration of 15 to 35 m in the above-mentioned aqueous electrolyte.

10. In Paragraph 1, A water-based lithium-ion battery in which the negative electrode active material included in the above negative electrode active material layer is lithium titanate or Wadsley-Roth niobate.

11. In Paragraph 1, The positive active material included in the above positive active material layer is LiMn (2-x) M x Aqueous lithium-ion battery, O4 (M is Ni or Co, 0≤x≤1).

12. In Paragraph 1, A water-based lithium-ion battery, wherein at least one active material layer among the positive active material layer and the negative active material layer comprises active material particles coated with the two ionic polymers.

13. In Paragraph 12, A water-based lithium-ion battery, wherein the amphoteric polymer is contained in an amount of 0.5 to 5 parts by weight per 100 parts by weight of active material particles contained in at least one active material layer among the positive active material layer and the negative active material layer.

14. In Paragraph 1, A water-based lithium-ion battery in which the two ionic polymers and active material particles are dispersed and located within at least one active material layer among the positive active material layer and the negative active material layer.

15. In Paragraph 1, A water-based lithium-ion battery comprising, between the positive electrode active material layer and the negative electrode active material layer, a biionic polymer together with the water-based electrolyte.

16. In Paragraph 15, A water-based lithium-ion battery in which, when the total weight of the water-based electrolyte and the amphoteric polymer is 100, the amphoteric polymer is contained in an amount of 0.04 to 20 parts by weight.

17. In Paragraph 15, A water-based lithium-ion battery in which the concentration of the above-mentioned two ionic polymers decreases from the region adjacent to the positive active material layer or the negative active material layer toward the inner region.

18. A step of providing a positive electrode including a positive active material layer and a negative electrode including a negative active material layer; A step of assembling a battery by placing an aqueous electrolyte between the anode and the cathode, the electrolyte comprising a lithium salt and an aqueous solvent, wherein the mass of the lithium salt is greater than the mass of the aqueous solvent; The above-mentioned assembled battery is aged to allow the aqueous electrolyte to penetrate into the positive active material layer and the negative active material layer, wherein at least one active material layer among the positive active material layer and the negative active material layer in the aged battery comprises monomers having both ionic functional groups together with the aqueous electrolyte; and A method for manufacturing an aqueous lithium-ion battery, comprising the step of polymerizing the monomers in the aged battery to form an amphoteric polymer in at least one active material layer among the positive active material layer and the negative active material layer.

19. In Paragraph 18, A method for manufacturing an aqueous lithium-ion battery in which the above polymerization is performed using thermal polymerization or electrochemical polymerization.

20. In Paragraph 19, A method for manufacturing an aqueous lithium-ion battery in which the above electrochemical polymerization is performed by carrying out a constant current charge-discharge cycle on the assembled battery.

21. In Paragraph 19, A method for manufacturing an aqueous lithium-ion battery in which the above electrochemical polymerization is performed by aging the assembled battery in a charged state and then discharging it.

22. In Paragraph 18, A method for manufacturing an aqueous lithium-ion battery, wherein, in the step of providing the positive electrode and the negative electrode, at least one active material layer among the positive active material layer and the negative active material layer comprises active material particles coated with the monomers.

23. In Paragraph 18, A method for manufacturing an aqueous lithium-ion battery, wherein, in the step of providing the positive electrode and the negative electrode, at least one active material layer among the positive electrode active material layer and the negative electrode active material layer is an active material layer in which the monomers and active material particles are mixed.

24. In Paragraph 18, A method for manufacturing an aqueous lithium-ion battery, wherein, in the step of assembling the battery, a mixture of the aqueous electrolyte and the monomers is disposed between the positive electrode and the negative electrode.

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