Solid electrolyte for lithium-ion battery, manufacturing method thereof, and lithium-ion battery including same

Abstract

Provided is a solid electrolyte for a lithium-ion battery, the solid electrolyte comprising: a network to which quaternary cellulose including cellulose oxide and a functional group having nitrogen are bonded; and lithium ions bonded to the network.

Description

Solid electrolyte for lithium-ion batteries, method for producing the same, and lithium-ion batteries containing the same

[0001] The present application relates to a solid electrolyte for a lithium ion battery, a method for producing the same, and a lithium ion battery including the same, and more specifically, to a solid electrolyte for a lithium ion battery having improved ionic conductivity and mechanical strength, a method for producing the same, and a lithium ion battery including the same.

[0002]

[0003] As the secondary battery industry rapidly grows beyond the existing small devices and home appliances into medium- and large-scale high-energy applications such as electric vehicles and energy storage systems (ESS), the market value of the secondary battery industry, which was only about $22 billion in 2018, is projected to grow to about $118 billion in 2025.

[0004] In this way, in order for secondary batteries to be utilized in medium- to large-scale energy storage media, price competitiveness, energy density, and / or stability that are significantly improved compared to the current level may be required.

[0005] In accordance with these technical needs, research on secondary batteries using solid electrolytes is being actively conducted. For example, International Patent Publication No. WO2014200198A1 discloses a composite electrode-composite electrolyte combination in which a composite electrode layer and a composite electrolyte layer are integrated, wherein the composite electrode layer includes a current collector and an electrode mixture layer formed on the current collector, the electrode mixture layer includes an electrode active material, a conductive material, a crosslinked polymer matrix, a dissociable salt, and an organic solvent, the composite electrolyte layer includes a crosslinked polymer matrix, inorganic particles, a dissociable salt, and an organic solvent, and the electrode mixture layer and the composite electrolyte layer are overlapped and physically bonded. For another example, Korean Patent Publication No. 10-1734301 discloses a method for producing a sol, comprising: a first step of reacting a first metal precursor composed of a Li precursor, a second metal precursor composed of an Al precursor, a third metal precursor composed of a Ti precursor, and a P precursor with a chelating agent to produce a sol; a second step of heating the sol to produce a gel; a third step of heating the gel to thermally decompose it; a fourth step of heat-treating the thermally decomposed gel by bringing it into contact with air; a fifth step of cooling the powder obtained through the fourth step; a sixth step of mixing 0.2 to 1 wt% of a sintering aid Bi2O3 into the powder cooled in the fifth step; and a seventh step of pressurizing and sintering the mixed powder obtained in the sixth step at 850°C while bringing it into contact with air, wherein the sintered body has a relative density (%) of 90.0 to 99.7 and an ionic conductivity (S cm). -1 ) is 7.9Х10 -4 9.9Х10 -4 A method for manufacturing a solid electrolyte for a lithium battery characterized by having a

[0006] However, solid electrolytes for secondary batteries currently have low ionic conductivity, insufficient mechanical strength and flexibility, poor interface stability, complex and high-cost manufacturing processes, temperature dependence, poor thermal stability, and limited scalability.

[0007] Accordingly, a solid electrolyte that can overcome existing limitations is required.

[0008]

[0009] The technical problem to be solved by the present application is to provide a solid electrolyte for a lithium ion battery having an amorphous phase by inducing an amorphous structure by a solvent, a method for producing the same, and a lithium ion battery including the same.

[0010] Another technical problem to be solved by the present application is to provide a solid electrolyte for a lithium ion battery, which can easily store OH ions for a long time without substantial loss and has improved ion mobility for OH ions, a method for producing the same, and a lithium ion battery including the same.

[0011] Another technical problem that the present application seeks to solve is to provide a solid electrolyte for a lithium-ion battery, a method for manufacturing the same, and a lithium-ion battery including the same, which is efficient because the manufacturing process steps are simplified and the process cost is reduced.

[0012] Another technical problem to be solved by the present application is to provide a solid electrolyte for a lithium ion battery, in which ionic conductivity is maximized by organic ionic plastic crystals (OIPC), a method for producing the same, and a lithium ion battery including the same.

[0013] The technical problems that this application seeks to solve are not limited to those described above.

[0014]

[0015] To solve the above technical problem, the present application provides a solid electrolyte for a lithium ion battery.

[0016] According to one embodiment, the solid electrolyte for a lithium ion battery may include a network in which oxidized cellulose and quaternized cellulose including a functional group having nitrogen are combined, and lithium ions combined with the network.

[0017] According to one embodiment, the lithium ion battery further comprises an intermediate that is ion-exchanged with the lithium ion and remains, wherein the intermediate may not participate in the charge and discharge reactions of the lithium ion battery.

[0018] In one embodiment, the intermediate in the network may be less than the lithium ion.

[0019] In one embodiment, the intermediate may comprise copper ions.

[0020]

[0021] To solve the above technical problem, the present application provides a solid electrolyte for a lithium ion battery.

[0022] According to one embodiment, the solid electrolyte for a lithium ion battery may include a network in which oxidized cellulose and quaternized cellulose having a functional group having nitrogen are bonded, lithium ions bonded to the network, and organic ionic plastic crystals bonded to the network to which the lithium ions are bonded.

[0023] In one embodiment, the organic ionic plastic crystals can be bonded to -NH or -O of the network.

[0024]

[0025] To solve the above technical problem, the present application provides a lithium ion battery.

[0026] According to one embodiment, the lithium ion battery may include the solid electrolyte, a positive electrode provided on one side of the solid electrolyte, and a metal negative electrode provided on the other side of the solid electrolyte.

[0027]

[0028] To solve the above technical problem, the present application provides a method for manufacturing a solid electrolyte for a lithium ion battery.

[0029] According to one embodiment, the method for producing a solid electrolyte for a lithium ion battery may include the steps of: producing a cellulose gel by reacting oxidized cellulose and quaternized cellulose in a solvent; providing the cellulose gel on a substrate and drying it to obtain a membrane; providing the membrane in a solution containing an intermediate to be ion-exchanged, thereby producing an intermediate-bound membrane in which the intermediate is bound to the membrane; and producing a solid electrolyte by ion-exchanging the intermediate with lithium ions in the intermediate-bound membrane using a solution containing lithium ions and the solvent.

[0030] According to one embodiment, the method for manufacturing a solid electrolyte for a lithium ion battery further includes, before the ion exchange, a step of providing the solvent to the intermediate binding membrane, and in the process for manufacturing the solid electrolyte, the solvent may be provided two or more times and four or less times as the same substance.

[0031] In one embodiment, the solvent can induce an amorphous structure that increases the flexibility of the cellulose chains, enhances the structural stability of the cross-linked network, and disrupts the crystallinity of the cellulose chains, thereby increasing the ionic conductivity of the solid electrolyte.

[0032] According to one embodiment, the solvent may have a dielectric constant of 32.2 or greater and 46.5 or less.

[0033] According to one embodiment, the ion exchange may be performed for 24 hours or more and 48 hours or less.

[0034] According to one embodiment, the method comprises adding a filler to the oxidized cellulose and the quaternized cellulose in the solvent to increase ionic conductivity, wherein the filler may include an organic ionic plastic crystal.

[0035] According to one embodiment, the method for producing a solid electrolyte for a lithium ion battery may further include a step of preparing cellulose, a step of oxidizing the cellulose to produce the oxidized cellulose, and a step of providing a secondary amine source to the cellulose to produce the quaternized cellulose including a functional group having nitrogen.

[0036] In one embodiment, the membrane may be provided to a solution containing the intermediate until the membrane turns blue.

[0037]

[0038] According to an embodiment of the present application, a solid electrolyte for a lithium ion battery can be provided, comprising a network in which oxidized cellulose and quaternized cellulose including a functional group having nitrogen are combined, and lithium ions combined with the network.

[0039] According to an embodiment of the present application, bacterial cellulose combined with chitosan as cellulose for forming the network can be used.

[0040] Due to this, OH ions can be easily stored for a long time without substantial loss within the solid electrolyte by the chitosan, and ion mobility for OH ions can be improved.

[0041] Additionally, according to an embodiment of the present application, cellulose acetate, which is commercially available, can be used as the cellulose.

[0042] Due to this, the manufacturing process steps for manufacturing the solid electrolyte can be simplified and the process cost can be reduced, making it efficient.

[0043] In addition, according to an embodiment of the present application, an organic ionic plastic crystal (OIPC) containing thiophenium and fluorohydrogenate as additives can be provided to the bacterial cellulose in which chitosan is bound to the cellulose.

[0044] Due to this, OH ions can be easily stored for a long time without substantial loss within the solid electrolyte by the chitosan, and ion mobility for OH ions can be improved, and the organic ionic plastic crystals (OIPC) can be bonded to -NH or -O of the network in which the oxidized cellulose and the quaternized cellulose are bonded, so that ion conductivity can be maximized.

[0045] In addition, according to an embodiment of the present application, an organic ionic plastic crystal (OIPC) containing thiophenium and fluorohydrogenate as additives can be provided to cellulose acetate, which is commercially available as the cellulose.

[0046] Due to this, the manufacturing process steps for manufacturing the solid electrolyte are simplified, the process cost is reduced, and it is efficient, and the organic ionic plastic crystals (OIPC) are bonded to -NH or -O of the network in which the oxidized cellulose and the quaternized cellulose are bonded, so that ionic conductivity can be maximized.

[0047]

[0048] FIG. 1 is a drawing for explaining a method for producing oxidized cellulose and quaternized cellulose according to an embodiment of the present application.

[0049] FIG. 2 is a drawing for explaining a method for manufacturing a solid electrolyte according to an embodiment of the present application.

[0050] Figure 3 is a drawing for explaining cellulose according to an embodiment of the present application.

[0051] FIG. 4 is a drawing for explaining oxidized cellulose according to an embodiment of the present application.

[0052] FIG. 5 is a drawing for explaining quaternized cellulose according to an embodiment of the present application.

[0053] Figure 6 is a drawing for explaining a cellulose gel according to an embodiment of the present application.

[0054] FIG. 7 is a drawing for explaining an intermediate binding membrane according to an embodiment of the present application.

[0055] FIG. 8 is a drawing for explaining a solid electrolyte according to an embodiment of the present application.

[0056] Figure 9 is a graph showing the ion conductivity according to the ion exchange process time in the manufacturing process of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-1 and 1-2 of the present application.

[0057] Fig. 10 is an x-ray diffraction (XRD) graph of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-1 and 1-2 of the present application.

[0058] Figure 11 is a Nyquist plot for analyzing the electrochemical impedance of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-1-1 and 1-1-2 of the present application.

[0059] Fig. 12 is a Nikist plot for analyzing the electrochemical impedance of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-2-1 to 1-2-4 of the present application.

[0060] Figure 13 shows the results of analysis of the solid electrolyte interphase (SEI) of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0061] Figure 14 is a photograph of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application (a) formed on a glass substrate and (b, c) optical photographs after separation from the glass substrate.

[0062] FIG. 15 is a scanning electron microscopy (SEM) image of a wrinkled region on (a) the top surface and (b) the bottom surface of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0063] FIG. 16 is a scanning electron microscope (SEM) image of a uniform area on (a) the top surface and (b) the bottom surface of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0064] Figure 17 is a scanning electron microscope (SEM) image of a cross-section of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0065] Figure 18 is a photograph taken while applying high voltage to a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0066] Figure 19 is a graph evaluating the performance of an electrochemical symmetric cell including a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0067] Figure 20 is a capacity analysis result of a lithium ion battery including a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0068] Figure 21 is a graph showing the ion conductivity according to the ion exchange process time in the manufacturing process of a solid electrolyte for a lithium ion battery according to Experimental Example 2-1 and Experimental Example 2-2 of the present application.

[0069] Figure 22 is a photograph of (a) a solid electrolyte for a lithium ion battery formed on a glass substrate according to Experimental Example 2 of the present application, and (b) an optical photograph after separation from the glass substrate.

[0070] Figure 23 is a graph evaluating the performance of an electrochemical symmetric cell including a solid electrolyte for a lithium ion battery according to Experimental Example 2 of the present application.

[0071] Figure 24 is a graph showing the ionic conductivity of each filler used in the manufacturing process of a solid electrolyte for a lithium ion battery according to Experimental Examples 3-1 to 3-3 of the present application.

[0072]

[0073] Hereinafter, preferred embodiments of the present application will be described in detail with reference to the attached drawings. However, the technical concepts of the present application are not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to sufficiently convey the concepts of the present application to those skilled in the art.

[0074] In this specification, when a component is referred to as being on another component, it means that the component may be formed directly on the other component, or a third component may be positioned between them. Furthermore, in the drawings, the shapes and thicknesses of regions are exaggerated for the purpose of effectively explaining the technical content.

[0075] Also, although terms such as first, second, and third have been used to describe various components in various embodiments of this specification, these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiments. Also, the term "and / or" has been used herein to mean including at least one of the components listed before and after.

[0076] In the specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof described in the specification, and should not be construed as excluding the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In addition, the term "connection" is used in the present specification to mean both indirectly connecting multiple components and directly connecting them.

[0077] Additionally, terms such as “part,” “unit,” and “module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software.

[0078] In addition, when describing the present application below, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present application, the detailed description will be omitted.

[0079]

[0080] FIG. 1 is a drawing for explaining a method for producing oxidized cellulose and quaternized cellulose according to an embodiment of the present application, FIG. 2 is a drawing for explaining a method for producing a solid electrolyte according to an embodiment of the present application, FIG. 3 is a drawing for explaining cellulose according to an embodiment of the present application, FIG. 4 is a drawing for explaining oxidized cellulose according to an embodiment of the present application, FIG. 5 is a drawing for explaining quaternized cellulose according to an embodiment of the present application, FIG. 6 is a drawing for explaining a cellulose gel according to an embodiment of the present application, FIG. 7 is a drawing for explaining an intermediate-bonded membrane according to an embodiment of the present application, and FIG. 8 is a drawing for explaining a solid electrolyte according to an embodiment of the present application.

[0081] Referring to FIGS. 1 and 3, cellulose (1) can be prepared (S110).

[0082] According to one embodiment, the cellulose (1) may be produced from a bacterial strain cultured in a culture medium containing a chitosan derivative. That is, the cellulose (1) may be bacterial cellulose to which chitosan is bound. When the cellulose (1) is bacterial cellulose to which chitosan is bound, OH ions can be easily stored for a long time without substantial loss in a solid electrolyte (100, see FIG. 8) produced by the chitosan, and ion mobility for OH ions can be improved.

[0083] Alternatively, commercially available cellulose may be prepared as the cellulose (1). Specifically, the cellulose (1) may be cellulose acetate. However, the present invention is not limited thereto. When commercially available cellulose is used, the manufacturing process steps for manufacturing the solid electrolyte (100) can be simplified, and the process costs can be reduced, making it efficient.

[0084] Continuing with reference to FIGS. 1 and 4, the cellulose (1) may be oxidized to produce oxidized cellulose (10) (S120). Specifically, the cellulose (1) may be oxidized using TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl). However, the present invention is not limited thereto.

[0085] Referring to Fig. 4, the surface of the oxidized cellulose (10) can be oxidized.

[0086] Accordingly, when the oxidized cellulose (10) is combined with the quaternized cellulose (20) described below to form a network, OH ions can hop (grotthuss transport) on the surface of the network where the oxidized cellulose (10) and the quaternized cellulose (20) are combined. Furthermore, OH ions can diffuse and move in the interior spaced from the surface of the network. In addition, the solid electrolyte (100) to be manufactured can have an amorphous phase, and thus can have high ionic conductivity compared to a crystalline structure.

[0087] Continuing with reference to FIGS. 1 and 5, a secondary amine source is provided to the cellulose (1), so that a quaternized cellulose (20) including a nitrogen-containing functional group can be manufactured (S130). Specifically, the secondary amine source may be dimethylamine ((CH3)2NH). However, the present invention is not limited thereto. The nitrogen-containing functional group can be expressed as in the chemical formula below.

[0088] <Chemical formula>

[0089]

[0090] That is, the above quaternary cellulose (20) may include a quaternary ammonium group (quaternary N).

[0091] Referring to FIG. 5, the quaternized cellulose (20) may include a functional group having nitrogen on the surface.

[0092] Accordingly, when the quaternized cellulose (20) is combined with the oxidized cellulose (10) to form a network, OH ions can hop, i.e., move through the grooves, on the surface of the network where the oxidized cellulose (10) and the quaternized cellulose (20) are combined. Furthermore, OH ions can diffuse and move within the interior spaced from the surface of the network. In addition, the solid electrolyte (100) to be manufactured can have an amorphous phase, and thus, can have a higher ionic conductivity than a crystalline structure.

[0093] Continuing with reference to FIGS. 2 and 6, in a solvent, the oxidized cellulose (10) and the quaternized cellulose (20) are reacted to produce a cellulose gel (30) (S140).

[0094] According to an embodiment of the present application, in the manufacturing process of the solid electrolyte (100), the solvent may be provided 2 to 4 times as the same substance. More specifically, the solvent may be a solvent having a dielectric constant of 32.2 to 46.5. More specifically, for example, the solvent may be any one selected from the group including N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), sulfolane, or acetonitrile, and may be provided 3 times as the same substance. For example, the same DMF may be provided once in this step and twice and three times in subsequent steps as the solvent.

[0095] Due to this, in the solvent, the oxidized cellulose (10) and the quaternized cellulose (20) can react, making gelation easy, and the cellulose gel (30) can be easily manufactured.

[0096] Additionally, the solid electrolyte (100) manufactured from the cellulose gel (30) can be formed into a flexible soft film.

[0097] According to an embodiment of the present application, the solvent, for example, DMF, can act as a plasticizer during the reaction of the oxidized cellulose (10) and the quaternized cellulose (20) because it has high viscosity, dielectric constant, and boiling point.

[0098] Due to this, the flexibility of the cellulose chain formed by the above reaction is increased, the structural stability of the cross-linked network is strengthened, and the crystallinity of the cellulose chain is disturbed, thereby inducing an amorphous structure that increases the ionic conductivity of the solid electrolyte (100).

[0099] Accordingly, the manufactured solid electrolyte (100) may have an amorphous phase, and thus may have high ionic conductivity. When the solid electrolyte (100) has an amorphous structure, lithium ions (3, Li) are more readily absorbed than those in a crystalline structure. + , see Fig. 8) can be easily formed. More specifically, DMF can form C=C bonds in cellulose chains to transform the crystal structure, thereby causing longer cellulose chains to become entangled, thereby improving hydrophilicity and surface roughness. As a result, the mechanical strength of the solid electrolyte (100) being manufactured can be improved.

[0100] In contrast, in the manufacturing process of a solid electrolyte, when the solvent is a different substance, for example, DMF is provided once in this step and acetonitrile is provided twice and three times in subsequent steps, the manufactured solid electrolyte can be formed into a hard film.

[0101] Additionally, the solid electrolyte being manufactured may have a crystalline phase, which may result in a decrease in ionic conductivity.

[0102] However, according to an embodiment of the present application, in the manufacturing process of the solid electrolyte (100), the solvent may be provided 2 to 4 times with the same material, more specifically, a solvent having a dielectric constant of 32.2 to 46.5 may be provided 3 times with the same material.

[0103] Due to this, in the solvent, the oxidized cellulose (10) and the quaternized cellulose (20) can react, making gelation easy, and the cellulose gel (30) can be easily manufactured.

[0104] Additionally, the solid electrolyte (100) manufactured from the cellulose gel (30) can be formed into a flexible soft film.

[0105] Furthermore, since the manufactured solid electrolyte (100) has an amorphous phase, the ionic conductivity can be high.

[0106] According to one embodiment, in the present step (S140), a filler that increases ionic conductivity may be further added to the oxidized cellulose (10) and the quaternized cellulose (20) in the solvent. Specifically, the filler may be an organic ionic plastic crystal (OIPC). More specifically, the filler may be a compound in which cations and anions are combined. For example, the cation may be at least one selected from the group consisting of thiophenium, thiazolium, phosphoranium, thiazolidinium, imidazolium, pyrrolidinium, or oxathiouranium, and the anion may be at least one selected from the group consisting of fluorohydrogenate, cyano(nitroso)methanide, or tetrazolidine.

[0107] Due to this, the filler, i.e., the organic ionic plastic crystals (OIPC), can be bonded to the network in which the oxidized cellulose (10) and the quaternized cellulose (2) are bonded. More specifically, the organic ionic plastic crystals (OIPC) can be bonded to -NH or -O of the network.

[0108] Accordingly, the ionic conductivity of the manufactured solid electrolyte (100) can be high.

[0109] Continuing with reference to FIGS. 2, 6, and 7, the cellulose gel (30) is provided on a substrate and dried to obtain a membrane (40) (S150).

[0110] Continuing with reference to FIGS. 2 and 7, the membrane (40) is provided in a solution containing an ion-exchanged intermediate (2), and an intermediate-bonded membrane (50) in which the intermediate (2) is bonded to the membrane (40) can be manufactured (S160). Specifically, the intermediate (2) is a copper ion (CU 2+ ) may be.

[0111] According to one embodiment, the membrane (40) may be provided to a solution containing the intermediate (2) until the point at which it turns blue.

[0112] Due to this, the intermediate (2) can be bonded to the membrane (40), and the intermediate bonded membrane (50) can be manufactured.

[0113] According to one embodiment, in the intermediate binding membrane (50), the intermediate (2) can be ion-exchanged with lithium ions (3, see FIG. 8) in a subsequent step. After the intermediate (2) is ion-exchanged with the lithium ions (3), it remains in the network in which the oxidized cellulose (10) and the quaternized cellulose (20) are bound, but it remains less than the lithium ions in the network and can not participate in the charge and discharge reactions of the lithium ion battery.

[0114] Accordingly, since the intermediate (2) does not participate in the charge and discharge reactions of a lithium-ion battery, side effects, such as side reactions or by-products, within the lithium-ion battery can be minimized. As a result, the stability of the interface between the solid electrolyte (100) and the metal negative electrode in the lithium-ion battery can be improved.

[0115] In addition, since the intermediate (2) does not participate in the charge and discharge reactions of the lithium ion battery, the ion conduction path led by lithium ions (3) may not be interrupted, and accordingly, the ion conductivity of the solid electrolyte (100) may be high.

[0116] In addition, since the intermediate (2) does not participate in the charging and discharging reactions of a lithium-ion battery, the risk of overcharging or short circuiting, for example, dendrite induction, can be reduced. Accordingly, the major safety issues of lithium-ion batteries can be resolved.

[0117] In addition, since the intermediate (2) remains in an inactive state during the charging and discharging process of a lithium-ion battery, electrolyte decomposition or electrode deterioration that affects the cycle life of the lithium-ion battery can be minimized. Accordingly, the long-term stability of the lithium-ion battery can be excellent.

[0118] Furthermore, since the intermediate (2) functions only as an ion exchange intermediate and only a minimal amount remains in the final material, i.e., the lithium-ion battery, performance degradation due to residual impurities after the process can be minimized. This can enhance the reliability of the manufacturing process.

[0119] According to one embodiment, the solvent may be provided to the intermediate binding membrane (50) after the intermediate binding membrane (50) is manufactured and before ion exchange in a subsequent step.

[0120] According to an embodiment of the present application, in the manufacturing process of the solid electrolyte (100), the solvent may be provided three times as the same material, for example, DMF.

[0121] Due to this, residual impurities, such as hydroxide or aqueous solution reagents, can be easily removed from the intermediate binding membrane (50), and impurities can be minimized.

[0122] Continuing with reference to FIGS. 2 and 8, a solid electrolyte (100) may be manufactured by ion-exchanging the intermediate (2) with lithium ions (3) in the intermediate binding membrane (50) using a solution containing lithium ions (3) and the solvent (S170). For example, the ion exchange may be performed for 24 hours or more and 48 hours or less.

[0123] Due to this, the ionic conductivity of the manufactured solid electrolyte (100) can be high.

[0124] According to one embodiment, through the ion exchange, the intermediate (2) remains in the network in which the oxidized cellulose (10) and the quaternized cellulose (20) are combined after being ion-exchanged with the lithium ions (3), but remains less than the lithium ions in the network and can not participate in the charge and discharge reactions of the lithium ion battery.

[0125] Accordingly, since the intermediate (2) does not participate in the charging and discharging reactions of a lithium-ion battery, side effects, such as side reactions or by-products, within the lithium-ion battery can be minimized. As a result, the stability of the interface between the solid electrolyte (100) and the metal negative electrode in the lithium-ion battery can be improved.

[0126] In addition, since the intermediate (2) does not participate in the charge and discharge reactions of the lithium ion battery, the ion conduction path led by lithium ions (3) may not be interrupted, and accordingly, the ion conductivity of the solid electrolyte (100) may be high.

[0127] In addition, since the intermediate (2) does not participate in the charging and discharging reactions of a lithium-ion battery, the risk of overcharging or short circuiting, for example, dendrite induction, can be reduced. Accordingly, the major safety issues of lithium-ion batteries can be resolved.

[0128] In addition, since the intermediate (2) remains in an inactive state during the charging and discharging process of a lithium-ion battery, electrolyte decomposition or electrode deterioration that affects the cycle life of the lithium-ion battery can be minimized. Accordingly, the long-term stability of the lithium-ion battery can be excellent.

[0129] Furthermore, since the intermediate (2) functions only as an ion exchange intermediate and only a minimal amount remains in the final material, i.e., the lithium-ion battery, performance degradation due to residual impurities after the process can be minimized. This can enhance the reliability of the manufacturing process.

[0130] In addition, according to an embodiment of the present application, in the manufacturing process of the solid electrolyte (100), the solvent may be provided three times as the same material, for example, DMF.

[0131] Due to this, the intermediate (2) can be easily ion-exchanged with the lithium ion (3) through the solution containing the solvent and the lithium ion (3).

[0132]

[0133] According to the above described method for manufacturing a solid electrolyte for a lithium ion battery, a solid electrolyte (100) for a lithium ion battery can be provided, which includes a network in which the oxidized cellulose (10) and the quaternized cellulose (20) including the functional group having nitrogen are combined, and lithium ions (3) combined to the network.

[0134] According to an embodiment of the present application, the solid electrolyte (100) may further include the intermediate, i.e., copper ions (2), which are ion-exchanged with the lithium ions (3) and remain. The intermediate (2) remains less than the lithium ions (3) in the network and may not participate in the charge and discharge reactions of the lithium ion battery.

[0135] Accordingly, since the intermediate (2) does not participate in the charging and discharging reactions of a lithium-ion battery, side effects, such as side reactions or by-products, within the lithium-ion battery can be minimized. As a result, the stability of the interface between the solid electrolyte (100) and the metal negative electrode in the lithium-ion battery can be improved.

[0136] In addition, since the intermediate (2) does not participate in the charge and discharge reactions of the lithium ion battery, the ion conduction path led by lithium ions (3) may not be interrupted, and accordingly, the ion conductivity of the solid electrolyte (100) may be high.

[0137] In addition, since the intermediate (2) does not participate in the charging and discharging reactions of a lithium-ion battery, the risk of overcharging or short circuiting, for example, dendrite induction, can be reduced. Accordingly, the major safety issues of lithium-ion batteries can be resolved.

[0138] In addition, since the intermediate (2) remains in an inactive state during the charging and discharging process of a lithium-ion battery, electrolyte decomposition or electrode deterioration that affects the cycle life of the lithium-ion battery can be minimized. Accordingly, the long-term stability of the lithium-ion battery can be excellent.

[0139] Furthermore, since the intermediate (2) functions only as an ion exchange intermediate and only a minimal amount remains in the final material, i.e., the lithium-ion battery, performance degradation due to residual impurities after the process can be minimized. This can enhance the reliability of the manufacturing process.

[0140] In addition, in the method for manufacturing a solid electrolyte for a lithium ion battery described above, when a filler that increases ionic conductivity, i.e., an organic ionic plastic crystal (OIPC), is further added to the oxidized cellulose (10) and the quaternized cellulose (20) in the solvent, a solid electrolyte (100) for a lithium ion battery can be provided, which includes a network in which the oxidized cellulose (10) and the quaternized cellulose (20) including a functional group having nitrogen are bonded, the lithium ions (3) bonded to the network, and the organic ionic plastic crystal (OIPC) bonded to the network in which the lithium ions (3) are bonded.

[0141] According to an embodiment of the present application, the organic ionic plastic crystal (OIPC) can be bonded to -NH or -O of the network.

[0142] Accordingly, the ionic conductivity of the solid electrolyte (100) can be high.

[0143] Furthermore, according to an embodiment of the present application, a lithium ion battery can be provided, including the solid electrolyte (100), a positive electrode provided on one side of the solid electrolyte (100), and a metal negative electrode provided on the other side of the solid electrolyte (100).

[0144] According to an embodiment of the present application, in the solid electrolyte (100) of the lithium ion battery, when the cellulose (1) is bacterial cellulose to which chitosan is bound, OH ions can be easily stored for a long time without substantial loss within the solid electrolyte (100) by the chitosan, and ion mobility for OH ions can be improved.

[0145] Alternatively, in the case where cellulose (1) sold commercially is used as the solid electrolyte (100) of the lithium ion battery, the manufacturing process step for manufacturing the solid electrolyte (100) can be simplified and the process cost can be reduced, making it efficient.

[0146] In addition, according to an embodiment of the present application, in the manufacturing process of the solid electrolyte (100), the solvent may be provided two or more times and four or less times as the same material having a dielectric constant of 32.2 or more and 46.5 or less. For example, the same DMF may be provided three times as the solvent.

[0147] Due to this, in the solvent, the oxidized cellulose (10) and the quaternized cellulose (20) can react, making gelation easy, and the cellulose gel (30) can be easily manufactured.

[0148] Additionally, the solid electrolyte (100) manufactured from the cellulose gel (30) can be formed into a flexible soft film.

[0149] According to an embodiment of the present application, the solvent, for example, DMF, can act as a plasticizer during the reaction of the oxidized cellulose (10) and the quaternized cellulose (20) because it has high viscosity, dielectric constant, and boiling point.

[0150] Due to this, the flexibility of the cellulose chain formed by the above reaction is increased, the structural stability of the cross-linked network is strengthened, and the crystallinity of the cellulose chain is disturbed, thereby inducing an amorphous structure that increases the ionic conductivity of the solid electrolyte (100).

[0151] Accordingly, the solid electrolyte (100) may have an amorphous phase, and thus may have high ionic conductivity. When the solid electrolyte (100) has an amorphous structure, the ion transfer path of the lithium ions (3) may be formed more easily than when the solid electrolyte (100) has a crystalline structure. More specifically, DMF may form a C=C bond in a cellulose chain to modify the crystal structure, and thus, longer cellulose chains may become entangled, and hydrophilicity and surface roughness may be improved. As a result, the mechanical strength of the solid electrolyte (100) may be improved.

[0152] Due to this, the electrical and mechanical characteristics of the lithium ion battery including the solid electrolyte (100) can be excellent.

[0153]

[0154] Hereinafter, specific experimental examples and characteristic evaluation results according to embodiments of the present application are described.

[0155]

[0156] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-1) according to Experimental Example 1-1

[0157] Acetobacter xylinum was prepared as a bacterial strain.

[0158] A suspension of 1 g of chitosan chloride dissolved in 1% (v / v) aqueous acetic acid was treated with 1 M glycidyltrimethylammonium chloride in a nitrogen (N2) atmosphere at 65°C for 24 hours, precipitated, and filtered several times with ethanol to prepare a chitosan derivative.

[0159] A modified Hestrin-Schramm (HS) culture medium containing 2% w / v of the above chitosan derivative, 2% w / v of pineapple juice, 0.5% w / v of yeast, 0.5% w / v of peptone, 0.27 w / v% of sodium phosphate, and 0.115 w / v% of citric acid was prepared.

[0160] A bacterial pellicle was prepared by culturing the bacterial strain, Acetobacter xylinum, in the above culture medium for 7 to 10 days.

[0161] The bacterial pellicle was treated with 2% w / v sodium hydroxide / potassium hydroxide (NaOH / KOH) at 120°C for 6 hours to remove bacterial cell aggregates, then reacted with 1N hydrochloric acid (HCl) at 1:15 w / v for 30 minutes to remove excess reagent, and then rinsed with water until the pH became neutral, thereby producing the cellulose (1).

[0162] In the presence of 0.1 g of sodium bromide (NaBr), 3.1 g (12%) of sodium hypochlorite (NaClO), and 0.5 M of sodium hydroxide (NaOH), the cellulose (1) was reacted with TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) for 3 hours, and then washed with 0.5 M of hydrochloric acid (HCl) and deionized water to oxidize the cellulose (1), thereby producing the oxidized cellulose (10).

[0163] After reacting 35 ml of dimethylamine ((CH3)2NH), 1.25 g of lithium bromide (LiBr), 2.1 g of N-bromosuccinimide (C4H4BrNO2), and 3.2 g of triphenylphosphine (P(C6H5)3) at 80°C for 1 hour, the mixture was precipitated and washed in deionized water / ethanol, and freeze-dried overnight to produce the quaternized cellulose (20) containing the nitrogen-containing functional group.

[0164] In DMF, 1 wt% of glutaraldehyde was added as a crosslinking agent, and the oxidized cellulose (10) and the quaternized cellulose (20) were reacted to produce the cellulose gel (30). This corresponds to a process in which DMF was provided once among the processes in which the same DMF was provided a total of three times as the solvent in the example of the present application.

[0165] On a glass substrate, the cellulose gel (30) was provided and dried overnight to obtain the membrane (40).

[0166] Disperse a piece of copper wire in concentrated sodium hydroxide (NaOH) for 7 to 10 days, and the mobile copper ion (Cu) in the aqueous solution as the intermediate (2) 2+ ) was prepared. After the membrane (40) was immersed in the copper ion (2) for 3 to 24 hours until the membrane (40) changed from transparent to blue, it was washed with deionized water to manufacture an intermediate-bonded membrane (50) in which the intermediate (2) was bound to the membrane (40).

[0167] The intermediate binding membrane (50) was transferred to DMF to remove hydroxide and / or aqueous solution, which corresponds to a process in which DMF was provided twice among the processes in which the same DMF was provided a total of three times as the solvent in the embodiment of the present application.

[0168] In a glove box or dry room, the lithium ion (3, Li+ ) and DMF, the copper ions (2) and the lithium ions (3) were ion-exchanged in the intermediate binding membrane (50) for 24 to 48 hours, which corresponds to a process in which DMF was provided three times among the processes in which the same DMF was provided three times in total as the solvent in the embodiment of the present application.

[0169] After the above ion exchange, the solid electrolyte (ex1-1) for a lithium ion battery according to Experimental Example 1-1 was manufactured by drying at 50 to 60°C overnight.

[0170]

[0171] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-2) according to Experimental Example 1-2

[0172] In the above-described Experimental Example 1-1, the same acetonitrile was provided a total of three times instead of DMF as the solvent, thereby manufacturing a solid electrolyte (ex1-2) for a lithium-ion battery according to Experimental Example 1-2.

[0173]

[0174] The above-described Experimental Examples 1-1 and 1-2 can be summarized as shown in Table 1 below.

[0175] Cellulose (1) Solvent Experiment Example 1-1 (ex1-1) Bacterial cellulose bound to chitosan DMF 3 times Experiment Example 1-2 (ex1-2) Bacterial cellulose bound to chitosan Acetonitrile 3 times

[0176]

[0177] Figure 9 is a graph showing the ion conductivity according to the ion exchange process time in the manufacturing process of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-1 and 1-2 of the present application.

[0178] Referring to FIG. 9, in the experimental examples 1-1 and 1-2 (ex1-1, ex1-2), it can be confirmed that the ionic conductivity of the solid electrolyte (100) increases in the ranges of 0.4 to 7.3 mS / cm and 0.6 to 3.3 mS / cm, respectively, as the lithium ion (3) exchange process time in the DMF and acetonitrile solvents increases.

[0179] In particular, as shown in Fig. 9, it can be confirmed that the increase in ion conductivity is the greatest when the ion exchange is performed for 24 hours or more and 48 hours or less.

[0180] Accordingly, the excellent ion conductivity characteristics of the solid electrolyte (100) manufactured by performing the ion exchange for 24 hours or more and 48 hours or less can be proven.

[0181] In addition, according to Experimental Examples 1-1 and 1-2 (ex1-1, ex1-2) of the present application with reference to FIG. 9, in the process for manufacturing the solid electrolyte (100), the solvent was provided as the same substance a total of three times. That is, the same DMF was provided a total of three times (ex1-1), or the same acetonitrile was provided a total of three times (ex1-2).

[0182] Due to this, in the solvent, the oxidized cellulose (10) and the quaternized cellulose (20) can react, making gelation easy, and the cellulose gel (30) can be easily manufactured.

[0183] Additionally, the solid electrolyte (100) manufactured from the cellulose gel (30) can be formed into a flexible soft film.

[0184] Unlike the experimental examples of the present application, in the process of manufacturing a solid electrolyte, when the solvent is a different substance, for example, DMF is provided once, and acetonitrile is provided twice and three times in subsequent processes, the manufactured solid electrolyte can be formed into a hard film.

[0185]

[0186] Fig. 10 is an x-ray diffraction (XRD) graph of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-1 and 1-2 of the present application.

[0187] Referring to Fig. 10, it can be confirmed that the solid electrolyte (ex1-1) for a lithium ion battery according to the above experimental example 1-1 has a relatively more amorphous structure than the above experimental example 1-2 (ex1-2).

[0188] Accordingly, it can be proven that DMF according to the above experimental example 1-1 acts as a plasticizer during the reaction of the oxidized cellulose (10) and the quaternized cellulose (20) because it has high viscosity, dielectric constant, and boiling point.

[0189]

[0190] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-1-1) according to Experimental Example 1-1-1

[0191] In the above-described experimental example 1-1, the copper ions (2) and the lithium ions (3) were ion-exchanged for 24 hours to manufacture a solid electrolyte (ex1-1-1) for a lithium ion battery according to experimental example 1-1-1.

[0192]

[0193] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-1-2) according to Experimental Example 1-1-2

[0194] In the above-described experimental example 1-1, the copper ions (2) and the lithium ions (3) were ion-exchanged for 72 hours to manufacture a solid electrolyte (ex1-1-2) for a lithium ion battery according to experimental example 1-1-2.

[0195]

[0196] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-2-1) according to Experimental Example 1-2-1

[0197] In the above-described experimental example 1-2, the copper ions (2) and the lithium ions (3) were ion-exchanged for 12 hours to manufacture a solid electrolyte (ex1-2-1) for a lithium ion battery according to experimental example 1-2-1.

[0198]

[0199] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-2-2) according to Experimental Example 1-2-2

[0200] In the above-described experimental example 1-2, the copper ions (2) and the lithium ions (3) were ion-exchanged for 24 hours to manufacture a solid electrolyte (ex1-2-2) for a lithium ion battery according to experimental example 1-2-2.

[0201]

[0202] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-2-3) according to Experimental Example 1-2-3

[0203] In the above-described experimental example 1-2, the copper ions (2) and the lithium ions (3) were ion-exchanged for 48 hours to manufacture a solid electrolyte (ex1-2-3) for a lithium ion battery according to experimental example 1-2-3.

[0204]

[0205] Manufacturing of a solid electrolyte for lithium-ion batteries (ex1-2-4) according to Experimental Example 1-2-4

[0206] In the above-described experimental example 1-2, the copper ions (2) and the lithium ions (3) were ion-exchanged for 72 hours to manufacture a solid electrolyte (ex1-2-4) for a lithium ion battery according to experimental example 1-2-4.

[0207]

[0208] The above-described experimental examples 1-1-1 to 1-2-4 can be summarized as shown in Table 2 below.

[0209] Classification Solvent Ion Exchange Time (h) Experiment Example 1-1-1 (ex1-1-1) DMF 3 times 24 Experiment Example 1-1-2 (ex1-1-2) DMF 3 times 72 Experiment Example 1-2-1 (ex1-2-1) Acetonitrile 3 times 12 Experiment Example 1-2-2 (ex1-2-2) Acetonitrile 3 times 24 Experiment Example 1-2-3 (ex1-2-3) Acetonitrile 3 times 48 Experiment Example 1-2-4 (ex1-2-4) Acetonitrile 3 times 72

[0210]

[0211] FIG. 11 is a Nyquist plot for analyzing the electrochemical impedance of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-1-1 and 1-1-2 of the present application, and FIG. 12 is a Nyquist plot for analyzing the electrochemical impedance of a solid electrolyte for a lithium ion battery according to Experimental Examples 1-2-1 to 1-2-4 of the present application.

[0212] Referring to FIGS. 11 and 12, it can be confirmed that the electrochemical impedance characteristics are the best when the ion exchange is performed for 24 hours or more and 48 hours or less.

[0213] Accordingly, the excellent ion conductivity characteristics of the solid electrolyte (100) manufactured by performing the ion exchange for 24 hours or more and 48 hours or less can be proven.

[0214]

[0215] Manufacturing of a solid electrolyte (ex1) for a lithium-ion battery according to Experimental Example 1

[0216] In the same manner as in Experimental Example 1-1 described above, a culture medium containing a chitosan derivative was prepared, and a solid electrolyte (ex1) for a lithium-ion battery according to Experimental Example 1 was prepared using bacterial cellulose bound to chitosan, which was prepared by culturing the bacterial strain Acetobacter xylinum in the culture medium.

[0217]

[0218] Manufacturing of a solid electrolyte (ex2) for a lithium-ion battery according to Experimental Example 2

[0219] In the above-described experimental example 1-1, a solid electrolyte (ex2) for a lithium-ion battery according to experimental example 2 was manufactured using commercially available cellulose acetate.

[0220]

[0221] Experimental examples 1 and 2 described above can be summarized as shown in Table 3 below.

[0222] Cellulose (1) Experimental example 1 (ex1) Bacterial cellulose combined with chitosan Experimental example 2 (ex2) Cellulose acetate sold on the market

[0223]

[0224] Figure 13 shows the results of analysis of the solid electrolyte interphase (SEI) of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0225] Figure 13 shows the results measured after 50 charge and discharge cycles at 0.5 C-rate after forming a lithium ion battery cell including a solid electrolyte (ex1), a cathode polymer structure (CPS), and a lithium metal anode according to the above experimental example 1.

[0226] Referring to Figure 13, it can be confirmed that peaks for inorganic phases related to Li-F and Li-S are dominantly observed over organic carbon-based phases. Additionally, peaks for small amounts of sulfonated or sulfurized components can also be confirmed.

[0227] Accordingly, it can be seen that in the SEI layer, most of the S and F originate from LiTFSI of the solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1.

[0228]

[0229] Figure 14 is a photograph of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application (a) formed on a glass substrate and (b, c) optical photographs after separation from the glass substrate.

[0230] Referring to Fig. 14, it can be seen that the solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 is formed with a thickness of 300 to 500 μm.

[0231]

[0232] FIG. 15 is a scanning electron microscopy (SEM) image of a wrinkled region on (a) the top surface and (b) the bottom surface of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application, and FIG. 16 is a scanning electron microscopy (SEM) image of a uniform region on (a) the top surface and (b) the bottom surface of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0233] Referring to FIGS. 15 and 16, it can be seen that the solid electrolyte (ex1) for a lithium ion battery according to the experimental example 1 has a mostly clean and smooth surface, although it is confirmed to be slightly rough and wrinkled in some areas.

[0234]

[0235] Figure 17 is a scanning electron microscope (SEM) image of a cross-section of a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0236] Referring to Fig. 17, it can be confirmed that the solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 has a very dense structure inside the cross-section and a clean surface outside the cross-section.

[0237]

[0238] Figure 18 is a photograph taken while applying high voltage to a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0239] Referring to FIGS. 18(a) to 18(c), it can be confirmed that the solid electrolyte (ex1) for a lithium ion battery according to the experimental example 1 above does not substantially cause physical damage, expansion, or other changes at a high pressure of 20 MPa or less.

[0240] On the other hand, referring to Fig. 18(d), it can be confirmed that the solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 starts to crack at a high pressure of 35 MPa or higher.

[0241] Accordingly, the excellent mechanical properties of the solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 can be demonstrated at a high pressure of less than 35 MPa.

[0242]

[0243] Figure 19 is a graph evaluating the performance of an electrochemical symmetric cell including a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0244] Figure 19 is a result measured when a solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 is placed between a pair of lithium metals to form an electrochemically symmetrical cell.

[0245] Referring to Fig. 19, an electrochemical symmetric cell including a solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 has a current of 5 mA / cm 2 It can be confirmed that it operates stably for 1400 hours at current density.

[0246] Thus, the symmetrical cell including the solid electrolyte (ex1) for lithium ion batteries according to the above experimental example 1 has a capacity of 2.5 mAh / cm 2 It can be proven that it can be operated stably for 1400 cycles with the corresponding area capacity.

[0247]

[0248] Figure 20 is a capacity analysis result of a lithium ion battery including a solid electrolyte for a lithium ion battery according to Experimental Example 1 of the present application.

[0249] FIG. 20(a) is a result of forming and measuring a lithium ion battery cell including a solid electrolyte (ex1), a cathode polymer structure (CPS), and a lithium metal anode according to the above Experimental Example 1, and FIG. 20(b) is a result of forming and measuring a lithium ion battery cell including a solid electrolyte (ex1), a lithium iron phosphate (LFP, LiFePO4) anode, and a lithium metal anode according to the above Experimental Example 1.

[0250] Referring to FIG. 20, it can be confirmed that the lithium ion battery cell including the cathode polymer structure (CPS) of FIG. 20(a) and the lithium ion battery cell including the lithium iron phosphate (LFP) cathode of FIG. 20(b) exhibit capacities of 479 mAh / g and 144 mAh / g at 1C-rate after 400 cycles and 250 cycles, respectively.

[0251] In the case of a lithium ion battery cell including a cathode polymer structure (CPS) as shown in Fig. 20(a), stability was shown for 400 cycles with a capacity retention rate of 89%, and in the case of a lithium ion battery cell including a lithium iron phosphate (LFP) cathode as shown in Fig. 20(b), stability was shown for more than 250 cycles with a capacity retention rate of 97%.

[0252] Accordingly, it can be proven that the solid electrolyte (ex1) for a lithium ion battery according to the above experimental example 1 operates stably with both a cathode polymer structure (CPS) and a lithium iron phosphate (LFP) cathode.

[0253]

[0254] Manufacturing of a solid electrolyte for lithium-ion batteries (ex2-1) according to Experimental Example 2-1

[0255] In the above-described Experimental Example 2, DMF was provided as the solvent a total of three times to manufacture a solid electrolyte (ex2-1) for a lithium-ion battery according to Experimental Example 2-1.

[0256]

[0257] Manufacturing of a solid electrolyte for lithium-ion batteries (ex2-2) according to Experimental Example 2-2

[0258] In the above-described Experimental Example 2, the same acetonitrile was provided a total of three times instead of DMF as the solvent, thereby manufacturing a solid electrolyte (ex2-2) for a lithium-ion battery according to Experimental Example 2-2.

[0259]

[0260] The above-described Experimental Examples 2-1 and 2-2 can be summarized as shown in Table 4 below.

[0261] Cellulose (1) Solvent Experiment Example 2-1 (ex2-1) Cellulose acetate sold commercially DMF 3 times Experiment Example 2-2 (ex2-2) Cellulose acetate sold commercially Acetonitrile 3 times

[0262]

[0263] Figure 21 is a graph showing the ion conductivity according to the ion exchange process time in the manufacturing process of a solid electrolyte for a lithium ion battery according to Experimental Example 2-1 and Experimental Example 2-2 of the present application.

[0264] Referring to Fig. 21, in the above Experimental Example 2-1 and Experimental Example 2-2 (ex2-1, ex2-2), it can be confirmed that the ionic conductivity of the solid electrolyte (100) increases in the range of 0.4 to 7.1 mS / cm and 0.5 to 3.1 mS / cm, respectively, as the lithium ion (3) exchange process time in the DMF and acetonitrile solvents increases.

[0265] Accordingly, it can be seen that the ionic conductivity of the DMF-based solid electrolyte (100) according to the above experimental example 2-1 (ex2-1) is higher than that of the acetonitrile-based solid electrolyte (100) according to the above experimental example 2-2 (ex2-2).

[0266] However, in the case of the acetonitrile-based solid electrolyte (100) according to the above experimental example 2-2 (ex2-2), there is a technical effect in that the manufacturing ease is high, the process time can be reduced to 1 / 10 compared to DMF, the toxicity, i.e., the toxic metabolism of by-products, is low, and the material unit cost can be reduced to 1 / 2 compared to DMF.

[0267] In addition, since the boiling point of DMF is 153°C while that of acetonitrile is 81°C, the acetonitrile-based solid electrolyte (100) according to the above experimental example 2-2 (ex2-2) has the advantage of being able to significantly shorten the drying time in the manufacturing process, and through this, there is a technical effect of being able to shorten the process time by more than 5 days compared to DMF even in a climate where the relative humidity in the summer reaches 99%.

[0268]

[0269] Figure 22 is a photograph of (a) a solid electrolyte for a lithium ion battery formed on a glass substrate according to Experimental Example 2 of the present application, and (b) an optical photograph after separation from the glass substrate.

[0270] Referring to Fig. 22, it can be seen that the solid electrolyte (ex2) for a lithium ion battery according to the above experimental example 2 is formed with a thickness of 300 to 500 μm.

[0271]

[0272] Figure 23 is a graph evaluating the performance of an electrochemical symmetric cell including a solid electrolyte for a lithium ion battery according to Experimental Example 2 of the present application.

[0273] Figure 23 is a result measured when a solid electrolyte (ex2) for a lithium ion battery according to the above experimental example 2 is placed between a pair of lithium metals to form an electrochemically symmetrical cell.

[0274] Referring to Fig. 23, an electrochemical symmetric cell including a solid electrolyte (ex2) for a lithium ion battery according to the above experimental example 2 has a current of 1 mA / cm 2 It can be confirmed that it operates stably for 700 hours at current density.

[0275] Thus, the symmetrical cell including the solid electrolyte (ex2) for lithium ion batteries according to the above experimental example 2 has a capacity of 0.5 mAh / cm 2 It can be proven that it can be operated stably for 700 cycles with the corresponding area capacity.

[0276]

[0277] Manufacturing of a solid electrolyte for lithium-ion batteries (ex3-1) according to Experimental Example 3-1

[0278] In the experimental example 1 described above, in DMF, an organic ionic plastic crystal (OIPC) containing 5 wt% of thiophenium cations and fluorohydrogenate anions as a filler was added to the crosslinking agent, the oxidized cellulose (10), and the quaternized cellulose (20), and ion-exchanged for 12 hours to manufacture a solid electrolyte (ex3-1) for a lithium ion battery according to experimental example 3-1.

[0279]

[0280] Manufacturing of a solid electrolyte for lithium-ion batteries (ex3-2) according to Experimental Example 3-2

[0281] In the above-described experimental example 3-1, succinonitrile was added as the filler, and a solid electrolyte (ex3-2) for a lithium-ion battery according to experimental example 3-2 was manufactured.

[0282]

[0283] Manufacturing of a solid electrolyte for lithium-ion batteries (ex3-3) according to Experimental Example 3-3

[0284] In the above-described Experimental Example 3-1, 2,2'-azobisisobutyronitrile was added as the filler, thereby manufacturing a solid electrolyte (ex3-3) for a lithium ion battery according to Experimental Example 3-3.

[0285]

[0286] The above-described experimental examples 3-1 to 3-3 can be summarized as shown in Table 5 below.

[0287] Example 3-1 of the filler experiment (ex3-1) Thiophenium and fluorohydrogenate Example 3-2 of the filler experiment (ex3-2) Succinronitrile Example 3-3 of the filler experiment (ex3-3) 2,2'-azobisisobutyronitrile

[0288]

[0289] Figure 24 is a graph showing the ionic conductivity of each filler used in the manufacturing process of a solid electrolyte for a lithium ion battery according to Experimental Examples 3-1 to 3-3 of the present application.

[0290] Referring to Fig. 24, in Experimental Examples 3-1 to 3-3 (ex3-1 to ex3-3), it can be confirmed that the ionic conductivity of the solid electrolyte (100) is high in the order of 5.1 mS / cm (ex3-1) when the filler is thiophenium and fluorohydrogenate, 3.5 mS / cm (ex3-2) when the filler is succinimide, and 2.8 mS / cm (ex3-3) when the filler is 2,2'-azobisisobutyronitrile.

[0291] Accordingly, according to the experimental example of the present application, when an organic ionic plastic crystal (OIPC) is added as the filler, it can be proven that the ionic conductivity of the solid electrolyte (100) is improved by bonding the organic ionic plastic crystal (OIPC) to -NH or -O of the network in which the oxidized cellulose (10) and the quaternized cellulose (20) are bonded.

[0292]

[0293] Manufacturing of a solid electrolyte (ex4) for a lithium-ion battery according to Experimental Example 4

[0294] In the above-described Experimental Example 2, in DMF, an organic ionic plastic crystal (OIPC) containing 5 to 10 wt% of thiophenium cations and fluorohydrogenate anions as a filler was added to the crosslinking agent, the oxidized cellulose (10), and the quaternized cellulose (20), thereby producing a solid electrolyte (ex4) for a lithium ion battery according to Experimental Example 4.

[0295]

[0296] Experimental examples 1 to 4 described above can be summarized as shown in Table 6 below.

[0297] Cellulose (1) Filler Experimental example 1 (ex1) Bacterial cellulose combined with chitosan - Experimental example 2 (ex2) Cellulose acetate sold commercially - Experimental example 3 (ex3) Bacterial cellulose combined with chitosan - Thiophenium and fluorohydrogenate Experimental example 4 (ex4) Cellulose acetate - Thiophenium and fluorohydrogenate sold commercially

[0298]

[0299] That is, according to Experimental Example 1 (ex1) of the present application, bacterial cellulose in which chitosan is bound to the cellulose (1) can be used.

[0300] Due to this, OH ions can be easily stored for a long time without substantial loss within the solid electrolyte (100) by the chitosan, and ion mobility for OH ions can be improved.

[0301] In addition, according to Experimental Example 2 (ex2) of the present application, cellulose acetate sold commercially can be used as the cellulose (1).

[0302] Due to this, the manufacturing process step for manufacturing the solid electrolyte (100) can be simplified and the process cost can be reduced, making it efficient.

[0303] In addition, according to Experimental Example 3 (ex3) of the present application, an organic ionic plastic crystal (OIPC) containing thiophenium and fluorohydrogenate as the additives can be provided to the bacterial cellulose in which chitosan is bound to the cellulose (1).

[0304] Due to this, OH ions can be easily stored for a long time without substantial loss within the solid electrolyte (100) by the chitosan, and ion mobility for OH ions can be improved, and the organic ionic plastic crystals (OIPC) can be bonded to -NH or -O of the network in which the oxidized cellulose (10) and the quaternized cellulose (20) are bonded, so that ion conductivity can be maximized.

[0305] In addition, according to Experimental Example 4 (ex4) of the present application, an organic ionic plastic crystal (OIPC) containing thiophenium and fluorohydrogenate as the additives can be provided to cellulose acetate, which is commercially available as the cellulose (1).

[0306] Due to this, the manufacturing process step for manufacturing the solid electrolyte (100) is simplified, the process cost is reduced, and it is efficient, and the organic ionic plastic crystal (OIPC) is bonded to -NH or -O of the network in which the oxidized cellulose (10) and the quaternized cellulose (20) are bonded, so that ionic conductivity can be maximized.

[0307]

[0308] While the present application has been described in detail using preferred embodiments, the scope of the present application is not limited to the specific embodiments and should be interpreted in accordance with the appended claims. Furthermore, those skilled in the art will appreciate that numerous modifications and variations are possible without departing from the scope of the present application.

Claims

1. A network comprising oxidized cellulose and quaternized cellulose containing a nitrogen-containing functional group; and A solid electrolyte for a lithium ion battery, comprising lithium ions bonded to the above network.

2. In paragraph 1, Further comprising the intermediate product remaining after ion exchange with the lithium ion, A solid electrolyte for a lithium-ion battery, comprising the intermediate that does not participate in the charge and discharge reactions of the lithium-ion battery.

3. In paragraph 2, A solid electrolyte for a lithium ion battery, wherein the intermediate in the above network comprises less lithium ions remaining than the above lithium ions.

4. In paragraph 2, The above intermediate is a solid electrolyte for a lithium ion battery, comprising copper ions.

5. A network comprising oxidized cellulose and quaternized cellulose containing a nitrogen-containing functional group; Lithium ions coupled to the above network; and A solid electrolyte for a lithium ion battery, comprising an organic ionic plastic crystal bonded to the network to which the lithium ions are bonded.

6. In paragraph 5, A solid electrolyte for a lithium ion battery, wherein the organic ionic plastic crystal comprises -NH or -O bonded to the network.

7. A solid electrolyte according to any one of paragraphs 1 and 5; An anode provided on one side of the solid electrolyte; and A lithium ion battery comprising a metal negative electrode provided on the other side of the solid electrolyte.

8. A step of producing a cellulose gel by reacting oxidized cellulose and quaternized cellulose in a solvent; A step of providing the cellulose gel on a substrate and drying it to obtain a membrane; A step of providing the membrane to a solution containing an ion-exchanged intermediate, thereby producing an intermediate-bound membrane in which the intermediate is bound to the membrane; and A method for producing a solid electrolyte for a lithium ion battery, comprising the step of producing a solid electrolyte by ion-exchanging the intermediate with lithium ions in the intermediate binding membrane using a solution containing lithium ions and the solvent.

9. In paragraph 8, Before the ion exchange, further comprising the step of providing the solvent to the intermediate binding membrane, A method for manufacturing a solid electrolyte for a lithium ion battery, wherein in the manufacturing process of the solid electrolyte, the solvent is provided two or more times and four or less times as the same substance.

10. In paragraph 8, The above solvent increases the flexibility of the cellulose chains and strengthens the structural stability of the cross-linked network. A method for manufacturing a solid electrolyte for a lithium ion battery, comprising inducing an amorphous structure that increases the ionic conductivity of the solid electrolyte by interfering with the crystallinity of the cellulose chain.

11. In paragraph 8, A method for producing a solid electrolyte for a lithium ion battery, wherein the solvent comprises a material having a dielectric constant of 32.2 or more and 46.5 or less.

12. In paragraph 8, A method for manufacturing a solid electrolyte for a lithium ion battery, wherein the ion exchange is performed for 24 hours or more and 48 hours or less.

13. In paragraph 8, Including adding a filler that increases ionic conductivity to the oxidized cellulose and the quaternized cellulose in the solvent, A method for manufacturing a solid electrolyte for a lithium ion battery, wherein the filler comprises an organic ionic plastic crystal.

14. In paragraph 8, Steps for preparing cellulose; A step of oxidizing the cellulose to produce the oxidized cellulose; and A method for producing a solid electrolyte for a lithium ion battery, further comprising the step of producing the quaternized cellulose containing a nitrogen-containing functional group by providing a secondary amine source to the cellulose.

15. In paragraph 8, A method for producing a solid electrolyte for a lithium ion battery, comprising providing the membrane to a solution containing the intermediate until the membrane turns blue.

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