Method for producing polymer solid electrolyte

Abstract

The present invention relates to a method for producing a polymer solid electrolyte, and the polymer solid electrolyte produced by freezing and thawing includes a cross-linked structure formed by a cross-linking functional group, and the cross-linked structure includes (a) a cross-link between the cross-linking functional groups, (b) a cross-link between the cross-linking functional group and a solvent, and (c) a bond between the cross-linking functional group and a lithium salt, so that the crystallinity of the polymer solid electrolyte can be reduced and the ionic conductivity can be improved without using a separate plasticizer. In addition, the method can be carried out in a continuous process and in a large volume.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0066932 filed May 31, 2022 and Korean Patent Application No. 10-2023-0070122 filed May 31, 2023, and incorporates all contents disclosed in the documents of said Korean patent applications as part of this specification.

[0002] The present invention relates to a method for producing a polymer solid electrolyte. [Background technology]

[0003] Lithium-ion batteries that use liquid electrolytes have a structure in which the negative and positive electrodes are separated by a separator, so if the separator is damaged by deformation or external impact, a short circuit can occur, which can lead to risks such as overheating and explosion. Therefore, the development of a solid electrolyte that can ensure safety is a very important issue in the field of lithium-ion secondary batteries.

[0004] Lithium secondary batteries using solid electrolytes have the advantages of increased battery safety and the ability to prevent electrolyte leakage, thereby improving battery reliability and facilitating the production of thin batteries. Furthermore, because lithium metal can be used in the anode, it is possible to improve energy density, making them attractive for applications such as small secondary batteries and large-capacity secondary batteries for electric vehicles, and are attracting attention as next-generation batteries.

[0005] Among solid electrolytes, polymer solid electrolytes may use either ion-conductive polymer materials or inorganic materials such as oxides or sulfides that have ion-conductive properties, but hybrid materials that combine polymer materials and inorganic materials have also been proposed.

[0006] Such conventional polymer solid electrolytes were manufactured through solution casting and high-temperature drying processes. However, conventional polymer solid electrolyte manufacturing technology had limitations in that it was difficult to manufacture polymer solid electrolytes with improved ionic conductivity due to the high crystallinity of crystalline or semi-crystalline polymers. In other words, the high crystallinity of polymers inhibits the chain mobility of polymers, restricting the movement of lithium ions within the polymer solid electrolyte, making it difficult to improve the ionic conductivity of the polymer solid electrolyte.

[0007] For example, conventional polymer solid electrolytes can be manufactured by forming a coating film using polyvinyl alcohol (PVA), which contains a hydroxyl group as a cross-linking functional group, as a polymer, followed by a high-temperature drying process. Specifically, the PVA is dissolved in water to prepare a PVA aqueous solution, which is then solution-cast onto a substrate to form a coating film. The PVA aqueous solution is then dried at room temperature or a high temperature to produce a PVA film-like polymer solid electrolyte. Here, high temperature refers to temperatures above 80°C, the glass transition temperature (Tg) of PVA. During the drying process, hydrogen bonds are formed between the cross-linking functional groups in the PVA after water evaporation. This hydrogen bonding causes polymer chain folding, resulting in an increase in the crystallinity of the polymer film. The higher the crystallinity, the more brittle the polymer film becomes. Highly crystallized and brittle polymer films exhibit reduced chain mobility, and if dissociated ions exist within the polymer film, ion mobility is significantly reduced. For this reason, typical PVA films produced by forming a coating film and then drying it at high temperatures as described above exhibit physical properties that are unsuitable for use as polymer solid electrolytes in lithium secondary batteries.

[0008] To overcome these limitations of polymer solid electrolytes, a technology has been developed to improve the mobility of polymer chains by adding a plasticizer to a crystalline or semi-crystalline polymer, thereby increasing the ionic conductivity of the polymer solid electrolyte. However, using a plasticizer can be difficult because it requires ensuring appropriate dispersion and miscibility between the polymer and plasticizer, making it difficult to set process conditions. Furthermore, using a liquid plasticizer reduces its compatibility with the polymer, making it difficult to perform the manufacturing process with a polymer solid electrolyte.

[0009] Therefore, there is a need for technological development of a method for manufacturing a polymer solid electrolyte in the form of a free-standing film that can be continuously processed without using additional additives such as plasticizers. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Chinese Patent Application Publication No. 112259788 Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a method for producing a polymer solid electrolyte that allows for improved ionic conductivity and a continuous process.

[0012] Another object of the present invention is to provide an all-solid-state battery including a polymer solid electrolyte produced by the above-mentioned production method. [Means for solving the problem]

[0013] Technical Solutions In order to achieve the above purpose, The present invention provides (1) preparing a polymer solid electrolyte-forming solution containing a polymer solution including a cross-linking functional group and a lithium salt; (2) unwinding the base film using an unwinder and feeding it to a conveying path; (3) applying the polymer solid electrolyte-forming solution onto the substrate film to form a coating film; (4) transporting the substrate film on which the coating film has been formed to a freezing section and freezing the coating film; (5) transferring the substrate film on which the frozen coating film is formed to a thawing section, and thawing the frozen coating film to prepare a polymer solid electrolyte layer; and (6) A method for producing a polymer solid electrolyte, comprising the step of winding and recovering the substrate film including the polymer solid electrolyte layer using a rewinder.

[0014] The present invention also provides an all-solid-state battery containing the polymer solid electrolyte produced by the production method of the present invention. [Effects of the Invention]

[0015] The method for preparing a polymer solid electrolyte according to the present invention reduces the crystallinity of the polymer by utilizing a cross-linked structure formed by cross-linking functional groups contained in the polymer and a structure including amorphous polymer chains, thereby improving ionic conductivity. Furthermore, these structural features can reduce brittleness, ductility, and viscosity.

[0016] Furthermore, the method for producing a polymer solid electrolyte according to the present invention allows for the production of a polymer solid electrolyte in a continuous process, making mass production possible. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a flowchart of a method for producing a polymer solid electrolyte of the present invention. [Figure 2] 1 is a graph showing the tendency of the ionic conductivity of the electrolyte depending on the molar ratio ([Li] / [OH]) of the cross-linkable functional group to the lithium salt. [Figure 3]Photographs showing the morphology of electrolytes depending on the molar ratio of cross-linking functional groups to lithium ([Li] / [OH]). DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will now be described in further detail to aid in its understanding.

[0019] The terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed in a way that is consistent with the technical idea of ​​the present invention, based on the principle that an inventor can appropriately define the concept of a term in order to best describe his or her invention.

[0020] The term "crosslinked structure" used herein refers to a structure including a three-dimensional frame formed by polymer chains and an internal space of the frame. The polymer chains are formed by crosslinking involving crosslinking functional groups contained in the polymer. The crosslinked structure has a three-dimensional shape and is formed by polymer chains intertwined with each other, so it can also be called a three-dimensional network structure.

[0021] Method for producing polymer solid electrolyte The present invention relates to a method for producing a polymer solid electrolyte, and the method for producing a polymer solid electrolyte of the present invention comprises the steps of: (1) preparing a polymer solid electrolyte-forming solution containing a polymer solution including a cross-linking functional group and a lithium salt; (2) unwinding the base film using an unwinder and feeding it to a conveying path; (3) applying the polymer solid electrolyte-forming solution onto the substrate film to form a coating film; (4) transporting the substrate film on which the coating film has been formed to a freezing section and freezing the coating film; (5) transferring the substrate film on which the frozen coating film is formed to a thawing section and thawing the frozen coating film to prepare a polymer solid electrolyte layer; and (6) The method includes a step of winding and recovering the substrate film including the polymer solid electrolyte layer using a rewinder.

[0022] The step (1) is a step of preparing an aqueous solution of a polymer containing a cross-linkable functional group and a solution for forming a polymer solid electrolyte containing a lithium salt.

[0023] In the present invention, the polymer containing cross-linkable functional groups is a polymer containing cross-linkable functional groups that can form a cross-linked structure by (a) cross-linking between cross-linkable functional groups, (b) cross-linking between the cross-linkable functional groups and a solvent, and (c) bonding between the cross-linkable functional groups and a lithium salt. The bonds (a), (b), and (c) will be described in more detail below.

[0024] For example, the cross-linkable functional group may include one or more selected from the group consisting of a hydroxyl group, a carboxyl group, and an amide group.

[0025] The weight-average molecular weight (Mw) of the polymer containing cross-linkable functional groups is 80,000 g / mol to 130,000 g / mol, specifically, 80,000 g / mol or more, 83,000 g / mol or more, or 85,000 g / mol or more, and 90,000 g / mol or less, 110,000 g / mol or less, or 130,000 g / mol or less. If the weight-average molecular weight (Mw) of the polymer containing cross-linkable functional groups is less than 80,000 g / mol, the bonds formed by the cross-linkable functional groups may not be sufficient to form a cross-linked structure. If the weight-average molecular weight (Mw) of the polymer containing cross-linkable functional groups exceeds 130,000 g / mol, the entanglement of polymer chains in the polymer aqueous solution increases, and the solvent penetration rate into the polymer chains decreases. This may accelerate gelation of the polymer, reduce the solubility of the polymer, and hinder smooth bonding by the cross-linking functional groups, making it difficult to form a cross-linked structure.

[0026] Furthermore, the polymer containing the cross-linkable functional group has the characteristic that phase separation between the polymer and the solvent occurs smoothly in the polymer solution, and the bonds (a), (b), and (c) are well formed by the cross-linkable functional group contained in the phase-separated polymer in the step (4) of freezing the coating film.

[0027] For example, the polymer containing the cross-linkable functional group may be polyvinyl alcohol (PVA), gelatin, methylcellulose, agar, dextran, poly(vinyl pyrrolidone), polyethylene oxide, poly(acrylic amide), poly(acrylic acid) (PAA), starch-carboxymethyl cellulose, hyaluronic acid-methylcellulose, chitosan, poly(N-isopropylacrylamide), and amino-terminated polyethylene glycol. Preferably, the polymer containing a cross-linkable functional group is polyvinyl alcohol, which is advantageous in that phase separation between the polyvinyl alcohol and the solvent is efficiently carried out in the step of freezing the coated film in step (4), and the polyvinyl alcohol forms a cross-linked structure through the bonds (a), (b), and (c) derived from the cross-linkable functional group of the polyvinyl alcohol phase-separated from the solvent.

[0028] In the present invention, the lithium salt is contained in a dissociated state in the internal space of the cross-linked structure, and can improve the ionic conductivity of the polymer solid electrolyte.

[0029] Furthermore, the lithium salt forms a bond with the cross-linking functional group (c) described below, thereby preventing the occurrence of crystallinity in the polymer solid electrolyte and simultaneously promoting the formation of amorphous polymer chains.

[0030] The lithium salts include LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, (CF3SO2)2NLi, and (FSO2)2NLi.

[0031] In the present invention, the molar ratio ([Li] / [G]) of the crosslinkable functional group ([G]) of the polymer containing the crosslinkable functional group to the lithium ([Li]) of the lithium salt contained in the polymer solid electrolyte is 0.1 or more and less than 0.5, specifically, more than 0.1, 0.2 or more, or 0.3 or more, and 0.4 or less, or less than 0.5. If the molar ratio ([Li] / [G]) is 0.1 or less, the content of the lithium salt may decrease, and the ionic conductivity of the polymer solid electrolyte may decrease. If the molar ratio ([Li] / [G]) is 0.5 or more, the content of the polymer containing the crosslinkable functional group may decrease, and the bonds (a), (b), and (c) may not be sufficiently formed, resulting in increased crystallinity and decreased ionic conductivity. If the crosslinkable functional group is a hydroxyl group (OH - ), the [G] can be expressed as [OH] or [O].

[0032] The solvent used in preparing the polymer solution is a polar solvent, such as water, that is, the polymer solution may be an aqueous polymer solution.

[0033] The concentration of the polymer solution containing a cross-linkable functional group can be appropriately adjusted to ensure smooth application of the polymer solid electrolyte-forming solution to a substrate film. For example, the polymer containing a cross-linkable functional group may be contained in an amount of 5 wt % to 20 wt % of the total weight of the polymer solution containing a cross-linkable functional group, specifically, 5 wt % or more, 7 wt % or more, or 9 wt % or more, and 13 wt % or less, 17 wt % or less, or 20 wt % or less. If the polymer containing a cross-linkable functional group is contained in an amount less than 5 wt %, the concentration may be too dilute and may run off during application to the substrate film. If the amount is more than 20 wt %, it may be difficult to dissolve the lithium salt at the desired concentration in the polymer solution, making it difficult to apply the solution in a uniform thin film.

[0034] The step (2) is a step of unwinding the base film using an unwinder and feeding it to a conveying path.

[0035] The unwinder unwinds and supplies the substrate film wound in a roll to a predetermined transport path, and can unwind and supply the substrate film by its own drive, and can finally unwind and supply the substrate film by the drive force of a rewinder that winds up the substrate film including the polymer solid electrolyte layer.

[0036] Therefore, the method for producing the polymer solid electrolyte of the present invention is a roll-to-roll process.

[0037] The substrate film is not particularly limited as long as it can function as a support on which the polymer solid electrolyte-forming solution is applied, and examples of the substrate film include stainless steel (SS), polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate copolymer film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, and polyimide film.

[0038] The step (3) is a step of coating the polymer solid electrolyte-forming solution on the substrate film to form a coating film.

[0039] The coating method in the present invention is not particularly limited as long as it can coat the polymer solid electrolyte-forming solution on the substrate film in the form of a film, for example, bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting.

[0040] In one embodiment of the present invention, a solution casting method can be used. More specifically, the polymer solid electrolyte forming solution prepared in step (1) above can be placed in a mixer, and the mixer can be positioned above a substrate film. The polymer solid electrolyte forming solution can be continuously cast onto the substrate film being fed through a transport path to form a coating film.

[0041] In step (4), the substrate film on which the coating film is formed is transported to a freezing section to freeze the coating film, and a polymer solid electrolyte can be produced in step (4). The polymer solid electrolyte of the present invention includes an amorphous polymer chain having a cross-linked structure and the cross-linkable functional group, and the cross-linked structure and the amorphous polymer chain having the cross-linkable functional group are formed by freezing the coating film. The polymer solid electrolyte of the present invention includes the amorphous polymer chain and a lithium salt in an internal space formed within the cross-linked structure, and the lithium salt is contained in a dissociated state.

[0042] The cross-linked structure is formed when some of the cross-linking functional groups contained in the polymer form localized crystallites, which act as cross-linkable junction points and cross-link. Here, the term "crystallites" refers to a knot-like structure resembling tangled threads, unlike a crystalline structure formed by folding of polymer chains.

[0043] The cross-linked structure includes (a) a cross-link between cross-linkable functional groups, (b) a cross-link between the cross-linkable functional group and a solvent, and (c) a bond between the cross-linkable functional group and a lithium salt, and the cross-linked structure is formed by the cross-linkable functional groups inducing the bonds of (a), (b), and (c).

[0044] In the present invention, the (a) cross-linking bond between the cross-linking functional groups includes a hydrogen bond between the cross-linking functional groups, and for example, the hydrogen bond is - The hydrogen bond between

[0045] If the cross-linked structure is composed only of cross-links between the (a) cross-linkable functional groups, the polymer solid electrolyte may become crystalline, possibly resulting in a decrease in ionic conductivity.

[0046] However, since the cross-linked structure includes not only (a) cross-links between the cross-linkable functional groups but also (b) cross-links between the cross-linkable functional groups and the solvent, and (c) cross-links between the cross-linkable functional groups and the lithium salt, the occurrence of crystallinity in the polymer solid electrolyte can be prevented.

[0047] In the present invention, the cross-linking between the (b) cross-linking functional group and the solvent may include a hydrogen bond. For example, the hydrogen bond may be an OH - and H + In this case, H + may be derived from an aqueous solvent.

[0048] The cross-linking between the cross-linkable functional group and the solvent in (b) refers to hydrogen bonding between the cross-linkable functional group and a portion of the solvent remaining after freezing and the thawing process in step (5) described below.

[0049] Furthermore, the crosslinking between the (b) crosslinkable functional group and the solvent interferes with the crosslinking between the (a) crosslinkable functional groups, and the crosslinked structure is not composed only of crosslinks between the (a) crosslinkable functional groups, thereby preventing an increase in the crystallinity of the polymer solid electrolyte. The solvent may contain water.

[0050] In the present invention, the bond between the (c) cross-linkable functional group and the lithium salt may include a bond due to Lewis acid-base interaction, for example, the bond may be a bond between OH - and Li + is a combination of

[0051] The bond between the (c) cross-linking functional group and the lithium salt interferes with the cross-linking between the (a) cross-linking functional groups and the cross-linking between the (b) cross-linking functional group and the solvent, and the cross-linked structure is not composed only of cross-links between the (a) cross-linking functional groups, thereby preventing the occurrence of crystallinity in the polymer solid electrolyte and promoting the formation of amorphous polymer chains. The more amorphous polymer chains are formed, the more the mobility of the polymer chains improves, which in turn increases the hopping effect of the lithium ions, and may improve the ionic conductivity of the polymer solid electrolyte.

[0052] In the present invention, the amorphous polymer refers to a polymer chain formed by cross-linking functional groups, which does not form crystals due to regular folding of the polymer chain, but exists in a free state of behavior. That is, the amorphous polymer chain includes a polymer containing cross-linking functional groups that do not form bonds such as (a), (b), and (c).

[0053] Due to the cross-linked structure, the polymer solid electrolyte is not easily broken or destroyed, and can function as an electrolyte support that stably contains lithium ions.

[0054] In addition, the amorphous polymer chains provide elasticity to the polymer solid electrolyte, minimizing brittleness, which is a property that makes the polymer solid electrolyte easily broken. The polymer chains also have excellent polymer chain mobility, which improves the mobility of lithium ions within the electrolyte, thereby providing a polymer solid electrolyte with improved ionic conductivity.

[0055] Furthermore, in step (4), phase separation may occur between the polymer and water contained in the aqueous polymer solution containing cross-linking functional groups used to form the coating film. This phase separation occurs because the strength of the hydrogen bonds between water molecules is stronger than that between the cross-linking functional groups and water molecules. The water molecules aggregated by the hydrogen bonds between water molecules exist as an ice phase due to the freezing in step (4). As a result, the number of cross-linking functional groups that form hydrogen bonds through their interaction with water molecules is significantly reduced.

[0056] That is, in the step of freezing the coating film, the polymer and water contained in the polymer aqueous solution must first undergo phase separation, and the phase separation is induced by hydrogen bonding between water molecules. As a result, the main target of the freezing step is the water molecules that induce phase separation. Alternatively, the targets of the freezing step after phase separation has been induced to a certain extent are the water molecules and the polymer.

[0057] Due to the phase separation, the inside of the coating film is divided into (i) a polymer-poor phase and (ii) a polymer-rich phase.

[0058] The (i) polymer-poor phase is a portion containing water molecules aggregated by hydrogen bonds between water molecules, and exists in an ice phase, which can also be called a free water state.

[0059] The (ii) polymer-rich phase is a region containing polymers that have phase-separated from water. The phase-separated polymers are polymers containing cross-linking functional groups that have been freed from interactions with water molecules. After phase separation, they are in a free state and do not form crystals through regular folding, but exist in a relatively free amorphous state, which is called an amorphous polymer chain.

[0060] In addition, some of the cross-linkable functional groups contained in the phase-separated polymer act as cross-linkable junction points where localized microcrystals can cross-link, forming a cross-linked structure including the bonds (a), (b), and (c).

[0061] The freezing of the coating film in step (4) can be carried out by appropriately selecting conditions sufficient to freeze the coating film. For example, the freezing temperature can be between -30°C and -10°C. Specifically, the freezing temperature is between -30°C, -25°C, or -23°C, and between -18°C, -15°C, or -10°C. If the freezing temperature is below -30°C, cracks may occur in the coating film. If the freezing temperature is above -10°C, phase separation between the polymer and water may be insufficient, making it difficult to form amorphous polymer chain regions. The freezing can be carried out for a period of 20 to 30 hours to ensure sufficient freezing.

[0062] The freezing section is located in a section where a coating film is formed on a substrate film and the substrate film on which the coating film is formed is transported to a rewinder, and is composed of a plurality of units.

[0063] Conventionally, polymer solid electrolytes have been manufactured through a high-temperature drying process, but in this case, the high crystallinity of crystalline or semi-crystalline polymers inhibits the mobility of polymer chains, restricting the movement of lithium ions within the polymer solid electrolyte and resulting in low ionic conductivity.

[0064] Therefore, in the present invention, a plasticizer is not used instead of a high-temperature drying process, and a freezing process is performed. This not only avoids the crystallization of the polymer, but also induces (a) cross-linking between the cross-linking functional groups, (b) cross-linking between the cross-linking functional groups and the solvent, and (c) bonding between the cross-linking functional groups and the lithium salt, due to the cross-linking functional groups contained in the polymer. As a result, a polymer solid electrolyte with improved ionic conductivity can be produced.

[0065] The step (5) is a step of conveying the substrate film on which the frozen coating film is formed to a thawing section to thaw the frozen coating film, thereby manufacturing a polymer solid electrolyte layer.

[0066] In step (5), the ice contained in the polymer-poor phase (i) melts and evaporates, thereby producing a polymer solid electrolyte with increased free volume.

[0067] The thawing can be performed by appropriately selecting conditions that allow the frozen coating film to be thawed to a degree that allows it to be applied to a polymer solid electrolyte. For example, the thawing temperature is 15°C to 35°C, or room temperature (25°C). If the thawing temperature is lower than 15°C, the efficiency of drying water after thawing (ice melting) may decrease, and if it exceeds 35°C, the coating film may shrink, causing wrinkles or warping.

[0068] As described above, the (4) step of freezing the coating film and the (5) step of thawing the frozen coating film induce the bonds of (a), (b), and (c), forming a cross-linked structure and forming amorphous polymer chains.

[0069] Therefore, steps (4) and (5) can be repeatedly performed, and the degree of cross-linked structure formation can be controlled by the number of repetitions. When steps (4) and (5) are considered to be one cycle, step (4) of freezing the coating film and step (5) of thawing the frozen coating film can be performed for one or more cycles, two or more cycles, three or more cycles, or five or more cycles. The upper limit of the cycles is not particularly limited, but may be 10 or less cycles, 13 or less cycles, or 15 or less cycles. As the number of cycles within this range increases, the degree of cross-linked structure formation increases, thereby increasing the modulus and strength of the polymer solid electrolyte.

[0070] When the thawing is completed in the step (5), the coating film can be used as a polymer solid electrolyte.

[0071] The thawing section is located within a section where the substrate film on which the frozen coating film is formed is transported to the rewinder, and is composed of a plurality of stages.

[0072] After step (5) and before step (6), the method may further include a step of immersing the polymer solid electrolyte layer in a liquid electrolyte and then drying it.

[0073] By further including this step, the ionic conductivity of the polymer solid electrolyte can be further improved by the liquid electrolyte, which is also contained in the inner space of the cross-linked structure.

[0074] The liquid electrolyte may be any liquid electrolyte commonly used in the art, and the composition of the liquid electrolyte is not particularly limited as long as it can be used in lithium secondary batteries. For example, the liquid electrolyte may include a lithium salt and a non-aqueous solvent. The lithium salt may be any one of the lithium salts described above. The non-aqueous solvent may include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), dioxolane (DOX), dimethoxyethane (DME), diethoxyethane (DEE), γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane.

[0075] The liquid electrolyte is contained in an amount of 1 to 5 wt % based on the total weight of the polymer solid electrolyte. If the content of the liquid electrolyte is less than 1 wt %, the effect of improving ion conductivity may be insignificant, and if it exceeds 5 wt %, stability may be reduced.

[0076] The step (6) is a step of winding and recovering the substrate film including the polymer solid electrolyte layer using a rewinder.

[0077] The rewinder can wind up the substrate film containing the polymer solid electrolyte in a roll and recover it, and can wind up the substrate film containing the polymer solid electrolyte layer by its own drive.

[0078] The recovered substrate film including the polymer solid electrolyte layer can be used as it is, or the polymer solid electrolyte layer can be used in the form of a free-standing film by additionally performing a step of separating the polymer solid electrolyte layer from the substrate film.

[0079] The freestanding film refers to a film that can maintain its film form by itself at room temperature and pressure without a separate support, i.e., without a substrate film.

[0080] The polymer solid electrolyte of the present invention exhibits elasticity, can minimize brittleness, and has the properties of a support that stably contains lithium ions, and is therefore in a suitable form as a polymer solid electrolyte.

[0081] The method for producing a polymer solid electrolyte of the present invention is a roll-to-roll process, which allows continuous production and mass production.

[0082] In the present invention, the ionic conductivity of the polymer solid electrolyte is 10 -4 S / cm or more.

[0083] The polymer solid electrolyte has low crystallinity and improved ionic conductivity due to its structural characteristics including the cross-linked structure, and as a result, despite being a solid electrolyte, it exhibits ionic conductivity at a level equal to or higher than that of conventional liquid electrolytes, thereby improving the performance of all-solid-state batteries.

[0084] All solid state battery The present invention also relates to an all-solid-state battery including the polymer solid electrolyte, the all-solid-state battery including a negative electrode, a positive electrode, and a polymer solid electrolyte interposed between the negative electrode and the positive electrode, the solid electrolyte being produced by the production method, and having the characteristics described above.

[0085] Specifically, the polymer solid electrolyte undergoes freezing and thawing processes to form physical cross-links, reducing crystallinity and improving ionic conductivity, making it suitable as an electrolyte for all-solid-state batteries.

[0086] In the present invention, the positive electrode included in the all-solid-state battery may include a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of a positive electrode current collector.

[0087] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0088] The positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions. For example, lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), Li[Ni x Co y Mn z M v ]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga, and In, and 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, and x+y+z+v=1), Li (Li a M b-a-b’ M' b’ )O 2-c A c (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2, M comprises one or more elements selected from the group consisting of Mn and Ni, Co, Fe, Cr, V, Cu, Zn, and Ti, M' is one or more elements selected from the group consisting of Al, Mg, and B, and A is one or more elements selected from the group consisting of P, F, S, and N), or compounds substituted with one or more transition metals, such as compounds of the formula Li 1+y Mn 2-y O4 (where y is 0-0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2, lithium copper oxide (Li2CuO2), vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7, and the chemical formula LiNi 1-y M y Ni-site lithium nickel oxide, represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01-0.3) 2-y M yExamples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M=Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01-0.1) or Li2Mn3MO8 (where M=Fe, Co, Co, Ni, Cu, or Zn), LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkali metal ion, disulfide compounds, and Fe2(MoO4)3.

[0089] The positive electrode active material is contained in an amount of 40 wt % to 80 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material is 40 wt % or more or 50 wt % or more and 70 wt % or less or 80 wt % or less. If the content of the positive electrode active material is less than 40 wt %, the connectivity between the wet positive electrode active material layer and the dry positive electrode active material layer may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be increased.

[0090] The binder is a component that assists in binding the positive electrode active material and the conductive material and binding them to the current collector, and is selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, polyphosphazene, polyacrylonite, The binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0091] The binder is contained in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer, and more specifically, the binder content is 1 wt % or more or 3 wt % or more and 15 wt % or less or 30 wt % or less. If the binder content is less than 1 wt %, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced. If the binder content exceeds 30 wt %, the adhesive strength is improved, but the content of the positive electrode active material is reduced accordingly, which may result in a decrease in battery capacity.

[0092] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples include graphite or conductive carbon. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, and lamp black; carbon-based substances having a graphene or graphite crystal structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more, but are not necessarily limited to these.

[0093] The conductive material is typically included in an amount of 0.5 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the conductive material content is 0.5 wt % or more, or 1 wt % or more, and 20 wt % or less, or 30 wt % or less. If the conductive material content is too low, such as less than 0.5 wt %, the effect of improving electrical conductivity may be difficult to expect, or the electrochemical characteristics of the battery may be degraded. If the conductive material content is too high, such as more than 30 wt %, the amount of positive electrode active material may be relatively small, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the positive electrode is not particularly limited, and conventional methods known in the art, such as coating the positive electrode active material, may be used.

[0094] The positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between an external conductor and the positive electrode active material layer.

[0095] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the all-solid-state battery and has high electronic conductivity. For example, the positive electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, palladium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, silver, or the like, or an aluminum-cadmium alloy.

[0096] The positive electrode current collector may have a fine uneven structure on its surface or a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer, and may therefore be in various forms such as a film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0097] The positive electrode can be manufactured by a conventional method. Specifically, the positive electrode can be manufactured by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent to form a positive electrode active material layer. The resulting composition is then applied to a positive electrode current collector, dried, and optionally compression-molded into a current collector to improve electrode density. Preferably, the organic solvent is one that can uniformly disperse the positive electrode active material, binder, and conductive material and that evaporates easily. Specific examples of the organic solvent include acetonitrile, methanol, ethanol, tetrahydrofuran, water, and isopropyl alcohol.

[0098] In the present invention, the negative electrode included in the all-solid-state battery may include a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0099] The negative electrode active material is a lithium ion (Li + ) reversibly intercalated or deintercalated, a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, lithium metal, or a lithium alloy.

[0100] The lithium ion (Li +The material capable of reversibly inserting or de-inserting lithium ions (Li) is, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The material capable of reversibly forming a lithium-containing compound by reacting with lithium (Li) is, for example, tin oxide, titanate, or silicon. The lithium alloy is, for example, an alloy of lithium (Li) and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0101] Preferably, the negative electrode active material is lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0102] The negative electrode active material may be included in an amount of 40 wt % to 80 wt % based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material is 40 wt % or more or 50 wt % or more and 70 wt % or less or 80 wt % or less. If the content of the negative electrode active material is less than 40 wt %, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be increased.

[0103] The binder is the same as that described above in the positive electrode active material layer.

[0104] The conductive material is the same as that described above for the positive electrode active material layer.

[0105] The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and examples of the negative electrode current collector that can be used include copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. Similarly to the positive electrode current collector, the negative electrode current collector can be in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc., with fine irregularities formed on the surface.

[0106] The method for manufacturing the anode is not particularly limited, and the anode may be manufactured by forming an anode active material layer on an anode current collector using a layer or film formation method commonly used in the art. For example, methods such as compression bonding, coating, and vapor deposition may be used. Furthermore, the anode of the present invention also includes a battery in which a thin lithium film is formed on the metal plate by initial charging after assembling the battery without a thin lithium film on the anode current collector.

[0107] The present invention also provides a battery module including the all-solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

[0108] In this case, specific examples of the device include, but are not limited to, power tools powered by electric motors, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters, electric golf carts, and power storage systems.

[0109] Preferred examples are shown below to aid in understanding the present invention. However, the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the category and technical idea of ​​the present invention, and it is natural that these changes and modifications also fall within the scope of the appended claims.

[0110] In the following examples and comparative examples, polymer solid electrolytes were prepared using polymers containing cross-linkable functional groups, the molar ratio of the cross-linkable functional groups to lithium ions, and whether or not a freezing / thawing process was applied, as shown in Table 1 below.

[0111] [Table 1]

[0112] Example 1 PVA (MW: 89,000 g / mol, degree of hydrolysis: >99%) was mixed with water to prepare a 10 wt% PVA aqueous solution. LiTFSI was added to the PVA aqueous solution and stirred to prepare a solution containing PVA, a polymer with cross-linkable functional groups, and LiTFSI, a lithium salt. The molar ratio ([Li] / [OH]) of the "OH" in the cross-linkable functional groups of the PVA to the "Li" in the lithium salt was adjusted to 0.4.

[0113] The solution was poured into a mixer and then applied by solution casting onto a substrate film (SS foil) fed to a conveying path by an unwinder. The film was then conveyed to a freezing section and frozen at -20°C for 24 hours, and then conveyed to a thawing section and thawed at 25°C to produce a polymer solid electrolyte layer on the substrate film. The substrate film containing the produced polymer solid electrolyte layer was wound and recovered using a rewinder. The substrate film was then peeled off to obtain a free-standing polymer solid electrolyte film.

[0114] Example 2 A polymer solid electrolyte was produced in the same manner as in Example 1, except that PVA having a weight-average molecular weight (Mw) of 85,000 g / mol was used.

[0115] Example 3 A polymer solid electrolyte was produced in the same manner as in Example 1, except that PVA having a weight-average molecular weight (Mw) of 100,000 g / mol was used.

[0116] Example 4 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the molar ratio ([Li] / [OH]) of the cross-linkable functional group “OH” of the PVA to the “Li” of the lithium salt was set to 0.1.

[0117] Example 5 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the molar ratio ([Li] / [OH]) of the cross-linkable functional group “OH” of the PVA to the “Li” of the lithium salt was set to 0.2.

[0118] Example 6 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the molar ratio ([Li] / [OH]) of the cross-linkable functional group "OH" of the PVA to the "Li" of the lithium salt was set to 0.3.

[0119] Comparative Example 1 A polymer solid electrolyte was produced in the same manner as in Example 1, except that a solution containing PVA, a polymer having a cross-linkable functional group, and LiTFSI, a lithium salt, was applied to an SS foil substrate, and then dried at 80°C.

[0120] Comparative Example 2 A polymer solid electrolyte was produced in the same manner as in Example 1, except that PEO, a polymer having no cross-linking functional groups, was used instead of PVA.

[0121] Comparative Example 3 A polymer solid electrolyte was produced in the same manner as in Comparative Example 1, except that a solution containing PVA, a polymer having a cross-linkable functional group, and LiTFSI, a lithium salt, was applied to an SS foil substrate, and then dried at room temperature (25°C).

[0122] Comparative Example 4 A polymer solid electrolyte was produced in the same manner as in Example 1, except that a 35% aqueous solution of poly(acrylic acid, PAA) (Mw: 100,000 g / mol) was used instead of PVA.

[0123] Comparative Example 5 A polymer solid electrolyte was produced in the same manner as in Example 1, except that PVA having a weight-average molecular weight (Mw) of 50,000 g / mol was used.

[0124] Comparative Example 6 A polymer solid electrolyte was produced in the same manner as in Example 1, except that PVA having a weight-average molecular weight (Mw) of 146,000 g / mol was used.

[0125] Comparative Example 7 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the molar ratio ([Li] / [OH]) of “OH” contained in the cross-linking functional group of PVA to “Li” of the lithium salt was set to 0.5.

[0126] Comparative Example 8 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the molar ratio of "OH" contained in the cross-linking functional group of PVA to "Li" of the lithium salt ([Li] / [OH]) was set to 0.52.

[0127] Experimental Example 1 In order to measure the ionic conductivity of the film-shaped polymer solid electrolytes prepared in the examples and comparative examples, a test was carried out using a 1.7671 cm 2 The solid polymer electrolyte was punched into a circle of the desired size, and the punched solid polymer electrolyte was placed between two pieces of stainless steel (SS) to prepare a coin cell.

[0128] Resistance was measured using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) at 25°C with an amplitude of 10 mV and a scan range of 500 kHz to 20 MHz, and the ionic conductivity of the polymer solid electrolyte was calculated using the following Equation 1:

[0129]

number

[0130] In the above formula 1, σ i is the ionic conductivity (S / cm) of the polymer solid electrolyte, R is the resistance (Ω) of the polymer solid electrolyte measured by the electrochemical impedance spectrometer, L is the thickness (μm) of the polymer solid electrolyte, and A is the area (cm 2 ) means

[0131] The ionic conductivity of the polymer solid electrolyte calculated using Equation 1, whether a freestanding film was formed, and the results of observing the appearance of the polymer solid electrolyte are shown in Table 2. Here, whether the freestanding film was formed (formed: O, not formed: X) and the appearance of the polymer solid electrolyte were observed with the naked eye.

[0132] [Table 2]

[0133] As shown in Table 2, it was confirmed that a polymer solid electrolyte in the form of a freestanding film can be prepared by using PVA having an appropriate molecular weight and a molar ratio ([Li] / [OH]) of the crosslinkable functional group to the lithium salt as the polymer containing the crosslinkable functional group, and by applying a freezing and thawing process (Examples 1, 2, 3, 5, and 6).

[0134] In Comparative Example 4, PAA was used as the polymer containing a cross-linkable functional group. Since PAA froze during the freezing step after the formation of the coating film and became liquid again during the thawing step, a free-standing film-like polymer solid electrolyte could not be produced.

[0135] In Comparative Example 5, the molecular weight of the PVA was low, so the electrolyte was produced in a liquid state, and a free-standing film-like polymer solid electrolyte could not be obtained.

[0136] In addition, in Comparative Example 6, the molecular weight of the PVA was so high that a solution for forming a coating film could not be obtained, and the electrolyte production process could not be carried out.

[0137] In addition, in Example 4, a brittle film was produced due to the low molar ratio of cross-linkable functional groups to lithium ([Li] / [OH]), and it was confirmed that the brittle film had significantly lower ionic conductivity than a free-standing film.

[0138] In addition, in Comparative Example 7, a high viscous gel was produced instead of a film due to the high molar ratio of cross-linkable functional groups to lithium ([Li] / [OH]). Although the gel had high ionic conductivity, it was in the form of a gel rather than a film, and it was confirmed that it was unsuitable for use as a polymer solid electrolyte. A gel state refers to a solid state with such low mechanical strength that it cannot be peeled off from the substrate, or a highly viscous liquid state, making it difficult to use as a polymer solid electrolyte.

[0139] In addition, in Comparative Example 8, the molar ratio of cross-linkable functional groups to lithium ([Li] / [OH]) was higher than in Example 1, resulting in the production of a highly viscous gel rather than a film. Although the gel had high ionic conductivity, it was confirmed that it was unsuitable for use as a polymer solid electrolyte because it was in the form of a gel rather than a film.

[0140] In Comparative Example 1, the electrolyte was prepared using a high-temperature drying process at 80°C, resulting in a highly viscous gel-like electrolyte. A uniform coating film could not be formed on the substrate, and bubbles, aggregation, and warping occurred during coating film formation.

[0141] Comparative Example 2 was an electrolyte prepared using PEO without cross-linking functional groups, and was in a liquid state rather than a film state.

[0142] Comparative Example 3 was a polymer solid electrolyte prepared using a room temperature drying process. Due to the absence of physical cross-links formed by the freezing and thawing processes, the polymer solid electrolyte had low mechanical strength and low ionic conductivity.

[0143] FIG. 2 is a graph showing the tendency of the ionic conductivity of the electrolyte depending on the molar ratio ([Li] / [OH]) of the cross-linkable functional group to the lithium salt.

[0144] Referring to FIG. 2, the molar ratio of lithium to cross-linking functional groups ([Li] / [OH], n Li / n PVA ) increases, the ionic conductivity of the polymer solid electrolyte increases. Comparative Example 3 was produced by a room temperature drying process, and it was found that the ionic conductivity was significantly low.

[0145] FIG. 3 is a photograph showing the electrolyte morphology depending on the molar ratio of cross-linkable functional groups to lithium ([Li] / [OH]).

[0146] Referring to FIG. 3, Example 4, in which the molar ratio of cross-linking functional groups to lithium ([Li] / [OH]) was 0.1, produced a brittle film, Comparative Example 7, in which the molar ratio was 0.5, produced a highly viscous gel, and Examples 1, 5, and 6, in which the molar ratio was greater than 0.1 and less than 0.5, produced film-shaped polymer solid electrolytes.

[0147] Example 7 A polymer solid electrolyte was produced in the same manner as in Example 1, except that two cycles of freezing and thawing were performed.

[0148] Example 8 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the freezing and thawing steps were repeated three times.

[0149] Example 9 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the freezing and thawing steps were repeated five times.

[0150] Example 10 A polymer solid electrolyte was produced in the same manner as in Example 1, except that the freezing and thawing process was repeated 10 times.

[0151] Comparative Example 9 PVA (MW: 89,000 g / mol; hydrolysis degree: >99%) was mixed with water to prepare a 10 wt% PVA aqueous solution, which was then coated onto SS foil and dried at high temperature (90°C for 3 hours) to prepare a PVA film.

[0152] Comparative Example 10 A PVA film was produced in the same manner as in Comparative Example 9, except that boric acid was added as a crosslinking agent.

[0153] Experimental Example 2 An experiment was carried out to compare the presence or absence of a cross-linked structure inside the polymer solid electrolyte and the degree of its formation.

[0154] Since the purpose of the comparison was to compare only the presence or absence and degree of formation of a crosslinked structure, the PVA film of Comparative Example 9, which did not contain a crosslinked structure, and Comparative Example 10, in which a chemical crosslinked structure was formed by a crosslinking agent, were used for comparison.

[0155] (1) Check the degree of swelling The test samples were immersed in water at room temperature (25°C) for 12 hours, and then the swelling degree of the samples was checked and evaluated according to the following criteria.

[0156] <Criteria for determining swelling degree> ◎: Swelled to 80% or more of the total volume.

[0157] ○: Swelled to 50% or more of the total volume.

[0158] △: Swelling of 20% or more of the total volume.

[0159] X: Swelling of less than 10% of the total volume.

[0160] (2) Modulus The modulus was measured on a Universal testing machine (UTM).

[0161] [Table 3]

[0162] Referring to Table 3, Examples 1 and 7 to 10, which are polymer solid electrolytes prepared by a freezing and thawing process, exhibited moduli above a certain level, and the swelling degree decreased as the number of freezing and thawing cycles increased. Generally, the swelling degree and mechanical properties of a polymer are significantly affected by the degree of crosslinking. The formation of crosslinking points increases the internal resistance of the polymer chain, resulting in increased swelling resistance and mechanical strength. In particular, the formation of physical crosslinks due to the freezing and thawing process is affected by the number of cycles. The results show that the modulus increases and the swelling degree decreases with increasing cycles, indicating that the crosslinked structure also increases with increasing cycles. Example 1 showed a swelling degree of 50% or more of the total volume, which was measured after 12 hours at room temperature, and is suitable for the properties required for polymer solid electrolytes for all-solid-state batteries.

[0163] It was found that the PVA film of Comparative Example 9 was swollen to 80% or more of its total volume, which indicates that no cross-linked structure was present inside the polymer.

[0164] The PVA film of Comparative Example 10 had a chemical cross-linked structure formed by adding boric acid as a cross-linking agent, and it was found that its modulus was lower than that of Comparative Example 9, in which no cross-linked structure was formed.

[0165] The PVA film of Comparative Example 10 had a reduced modulus compared to that of Comparative Example 9 due to the formation of a chemical cross-linked structure, reduced crystallinity, and increased polymer flexibility.

[0166] Meanwhile, Examples 1 and 7 to 10 correspond to PVA films in the form of hydrogels based on physical cross-linking formed using a freezing and thawing process, unlike the manufacturing methods of Comparative Examples 9 and 10. This shows a tendency for the modulus to increase as the degree of cross-linking increases. In Examples 1 and 7 to 10, the cross-linked structure increases as the number of freezing and thawing cycles increases, and the modulus also tends to increase. Through the freezing and thawing process, some of the cross-linking functional groups contained in the PVA form localized crystals, and these localized crystals act as cross-linkable junction points, increasing the modulus.

[0167] Although the present invention has been described above using limited examples and drawings, the present invention is not limited thereto, and it is understood that various modifications and variations can be made by a person having ordinary skill in the art to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims set forth below.

Claims

1. (1) preparing a solution for forming a polymer solid electrolyte by adding a lithium salt to a polymer solution containing a cross-linkable functional group, the polymer solution containing a cross-linkable functional group including a polymer containing a cross-linkable functional group and a solvent; (2) unwinding the base film using an unwinder and feeding it to a conveying path; (3) applying the polymer solid electrolyte-forming solution onto the substrate film to form a coating film; (4) transporting the substrate film on which the coating film has been formed to a freezing section and freezing the coating film; (5) transferring the substrate film on which the frozen coating film is formed to a thawing section and thawing the frozen coating film to form a polymer solid electrolyte layer; and (6) A method for producing a polymer solid electrolyte, comprising: winding and recovering the substrate film including the polymer solid electrolyte layer using a rewinder, The weight average molecular weight (Mw) of the polymer containing a crosslinkable functional group is 80,000 g / mol to 130,000 g / mol; The polymer containing a cross-linkable functional group includes polyvinyl alcohol (PVA), a molar ratio ([Li] / [G]) of lithium ([Li]) in the lithium salt to the cross-linkable functional group ([G]) in the polymer is greater than 0.1 and less than 0.

5.

2. 2. The method of claim 1, wherein the cross-linkable functional group comprises at least one selected from the group consisting of a hydroxyl group, a carboxyl group, and an amide group.

3. 2. The method of claim 1, wherein the weight average molecular weight (Mw) of the polymer having the cross-linkable functional group is 83,000 g / mol to 110,000 g / mol.

4. The lithium salt is LiNO ３ , LiOH, LiCl, LiBr, LiI, LiClO ４ , LiBF ４ , LiB １０ Cl １０ , LiPF ６ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiAlCl ４ , C.H. ３ SO ３ Li, CF ３ SO ３ Li, LiSCN, LiC(CF ３ SO ２ ) ３ , (CF ３ SO ２ ) ２ NLi, and (FSO ２ ) ２ 2. The method for producing a polymer solid electrolyte according to claim 1, wherein the polymer solid electrolyte comprises one or more selected from the group consisting of NLi.

5. 2. The method for preparing a polymer solid electrolyte according to claim 1, wherein the polymer having a cross-linkable functional group is contained in an amount of 5 to 20 wt % based on the total weight of the polymer solution having a cross-linkable functional group.

6. The method for producing a polymer solid electrolyte according to claim 1 , wherein the solvent of the polymer solution containing the cross-linking functional group is water.

7. 2. The method for producing a polymer solid electrolyte according to claim 1, wherein a molar ratio ([Li] / [G]) of lithium ([Li]) of the lithium salt to the cross-linkable functional group ([G]) of the polymer is 0.2 or more and 0.4 or less.

8. 2. The method for producing a polymer solid electrolyte according to claim 1, wherein the freezing is performed at a temperature of −30° C. to −10° C.

9. The method for producing a polymer solid electrolyte according to claim 1 , wherein the thawing is performed at 15° C. to 35° C.

10. The method for producing a polymer solid electrolyte according to claim 1 , wherein the freezing in step (4) and the thawing in step (5) are repeated.

11. The polymer solid electrolyte includes an amorphous polymer chain having a cross-linked structure and the cross-linkable functional group, the cross-linked structure includes (a) a cross-link between the cross-linking functional groups, (b) a cross-link between the cross-linking functional group and the solvent, and (c) a bond between the cross-linking functional group and the lithium salt; the cross-linking bond between the cross-linking functional groups (a) comprises a hydrogen bond, the cross-linking between the cross-linking functional group and the solvent (b) comprises a hydrogen bond; 2. The method for producing a polymer solid electrolyte according to claim 1, wherein the (c) bond between the cross-linkable functional group and the lithium salt includes a bond based on Lewis acid-base interaction.

12. The method for producing a polymer solid electrolyte according to claim 11 , wherein the solvent contains water.

13. The method for preparing a polymer solid electrolyte according to claim 11 , wherein the cross-linked structure and the amorphous polymer chains containing the cross-linkable functional groups are formed in step (4).

14. 2. The method for producing a polymer solid electrolyte according to claim 1, further comprising the step of immersing the polymer solid electrolyte layer in a liquid electrolyte and then drying it after the step (5) and before the step (6).

15. The ionic conductivity of the polymer solid electrolyte is 10 －４ 2. The method for producing a polymer solid electrolyte according to claim 1, wherein the surface roughness is 100 nm.

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